document_title: Vice President of the United States

question_text: who is the leader of the senate when the vp isn't there

question_tokens: who is the leader of the senate when the vp is n 't there

text: Vice President of the United States

text: Origin[edit]

text: No mention of an office of vice president was made at the 1787 Constitutional Convention until near the end, when an 11-member committee on "Leftover Business" proposed a method of electing the president and vice president, and recommended that the vice president succeed the executive in the event of a vacancy in that position, but would otherwise serve as the president of the Senate, casting a vote only to break a tie. Although delegates approved establishing the office, with both its executive and senatorial functions, not many understood the extent of the vice president's duties. Only a few states had an analogous position. Among those that did, New York's constitution provided that, "The lieutenant-governor shall, by virtue of his office, be president of the Senate, and, upon an equal division, have a casting voice in their decisions, but not vote on any other occasion."[9]

text: Convention delegates had previously considered the selection of the Senate's presiding officer, deciding that, "The Senate shall choose its own President," and had agreed that this official would be designated the executive's immediate successor. They had also considered the mode of election of the executive but had not reached consensus. This all changed on September 4, when the committee recommended that the nation's chief executive be elected by a group of electors apportioned among the states, with each state receiving a number of presidential electors equal to the sum of that state's allocation of representatives and senators.[10][11]

text: The formation of the office of vice president was a by-product of this recommendation. The proposed presidential election process called for each state to choose members of the electoral college who were mandated to vote for the candidate who had received most votes in their state. Recognizing that loyalty to one's individual state outweighed loyalty to the new federation, the Constitution's framers assumed that individual electors would be inclined to choose a candidate from their own state (a so-called "favorite son" candidate) over one from another. So they created the office of vice president and required that electors vote for two candidates, requiring that at least one of their votes must be for a candidate from outside the elector's state, believing that this second vote could be cast for a candidate of national character.[11][12] Additionally, to guard against the possibility that some electors might strategically throw away their second vote in order to bolster their favorite son's chance of winning, it was specified that the first runner-up presidential candidate would become vice president. Creating this new office imposed a political cost on strategically discarded electoral votes, incentivizing electors to make their choices for president without resort to electoral gamesmanship and to cast their second ballot accordingly.[11]

text: Roles of the vice president[edit]

text:
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text: The vice presidency was established primarily to provide a successor in the event of the president's death, disability, or resignation.[4][13] Vice presidents have two constitutionally mandated duties: to serve as President of the Senate (but without a vote, unless the Senate is evenly divided), and to receive from the states the tally of electoral ballots cast for president and vice president and to open the certificates during a joint session of Congress.[4] Other statutorily granted roles include membership of both the National Security Council and the Board of Regents of the Smithsonian Institution.[14][15]

text: President of the United States Senate[edit]

text: As President of the Senate (Article I, Section 3, Clause 4), the vice president has two primary duties: to cast a vote in the event of a Senate deadlock and to preside over and certify the official vote count of the Electoral College. For example, in the first half of 2001, the Senators were divided 50-50 between Republicans and Democrats. The Democrats had the majority from January 3 to noon January 20 with Al Gore's tie-breaking vote. Dick Cheney's tie-breaking vote gave the Republicans the Senate majority until June 6, 2001 when Jim Jeffords left the Republican Party.

text: Regular duties[edit]

text: The vice president oversees procedural matters in the Senate, and may cast a tie-breaking vote. There is a strong convention within the Senate that the vice president should not use his position as President of the Senate to influence the passage of legislation or act in a partisan manner, except in the case of breaking tie votes. As of February 2, 2018, a total of 262 tie-breaking votes had been cast by 36 vice presidents. As President of the Senate, John Adams cast 29 tie-breaking votes, a number later surpassed by John C. Calhoun with 31; no other vice president since then has ever threatened this record.[16] Adams's votes protected the president's sole authority over the removal of appointees, influenced the location of the national capital, and prevented war with Great Britain. On at least one occasion Adams persuaded senators to vote against legislation he opposed, and he frequently addressed the Senate on procedural and policy matters. Adams's political views and his active role in the Senate made him a natural target for critics of George Washington's administration. Toward the end of his first term, a threatened resolution that would have silenced him except for procedural and policy matters caused him to exercise more restraint in hopes of seeing his election as President of the United States.

text: Formerly, the vice president would preside regularly over Senate proceedings, but in modern times, the vice president rarely presides over day-to-day matters in the Senate; in their place, the Senate chooses a President pro tempore (or "president for a time") to preside in the vice president's absence; the Senate normally selects the longest-serving senator in the majority party. The President pro tempore has the power to appoint any other senator to preside, and in practice junior senators from the majority party are assigned the task of presiding over the Senate at most times.

text: Except for this tie-breaking role, the Standing Rules of the Senate vest no significant responsibilities in the vice president. Rule XIX, which governs debate, does not authorize the vice president to participate in debate, and grants only to members of the Senate (and, upon appropriate notice, former presidents of the United States) the privilege of addressing the Senate, without granting a similar privilege to the sitting vice president. Thus, as Time magazine wrote during the controversial tenure of Vice President Charles G. Dawes, "once in four years the Vice President can make a little speech, and then he is done. For four years he then has to sit in the seat of the silent, attending to speeches ponderous or otherwise, of deliberation or humor."[17]

text: Recurring, infrequent duties[edit]

text: The President of the Senate also presides over counting and presentation of the votes of the Electoral College. This process occurs in the presence of both houses of Congress, generally on January 6 of the year following a U.S. presidential election.[18] In this capacity, only four vice presidents have been able to announce their own election to the presidency: John Adams, Thomas Jefferson, Martin Van Buren, and George H. W. Bush. At the beginning of 1961, it fell to Richard Nixon to preside over this process, which officially announced the election of his 1960 opponent, John F. Kennedy. In 2001, Al Gore announced the election of his opponent, George W. Bush. In 1969, Vice President Hubert Humphrey would have announced the election of his opponent, Richard Nixon; however, on the date of the Congressional joint session (January 6), Humphrey was in Norway attending the funeral of Trygve Lie, the first elected Secretary-General of the United Nations. The president pro tempore presided in Humphrey's absence.[19]

text: In 1933, incumbent Vice President Charles Curtis announced the election of House Speaker John Nance Garner as his successor, while Garner was seated next to him on the House dais. The President of the Senate may also preside over most of the impeachment trials of federal officers. However, whenever the President of the United States is on trial, the Constitution requires the Chief Justice of the United States to preside. In 1986, the Senate extended this to cover vice presidents as well—the Constitution is silent as to who would preside in the instance where the vice president is the officer impeached.

text: Succession to the presidency[edit]

text: The U.S. Constitution (Article II, Section 1, Clause 6) provides that "In Case of the Removal of the President from Office, or of his Death, Resignation, or Inability to discharge the Powers and Duties of the said Office, the Same shall devolve on the Vice President, ..."[20] Initially, it was unclear whether this meant the vice president became the new president or merely an acting president. This was first tested in 1841 with the death of President William Henry Harrison. Harrison's vice president, John Tyler, asserted that he had succeeded to the full presidential office, powers, and title, and declined to acknowledge documents referring to him as "Acting President." Despite some strong calls against it, Tyler took the oath of office as the nation's tenth President. Although some in Congress denounced Tyler's claim as a violation of the Constitution,[20] it was not challenged legally, and so the Tyler precedent of full succession was established. This was made explicit by Section 1 of the Twenty-fifth Amendment to the United States Constitution, ratified in 1967. In total, nine incumbent Vice Presidents have succeeded to the presidency. In addition to Tyler they are, Millard Fillmore, Andrew Johnson, Chester A. Arthur, Theodore Roosevelt, Calvin Coolidge, Harry S. Truman, Lyndon B. Johnson, and Gerald Ford.

text: Presidential disabilities[edit]

text: Another issue was who had the power to declare that an incapacitated president is unable to discharge his duties. This question had arisen most recently with the illnesses of President Dwight D. Eisenhower. Sections 3 and 4 of the amendment provide means for the vice president to become acting president upon the temporary disability of the president. Section 3 deals with self-declared incapacity of the president. Section 4 deals with incapacity declared by the joint action of the vice president and of a majority of the Cabinet or of such other body as Congress may by law provide. While Section 4 has never been invoked, Section 3 has been invoked three times: on July 13, 1985 when Ronald Reagan underwent surgery to remove cancerous polyps from his colon, and twice more on June 29, 2002 and July 21, 2007 when George W. Bush underwent colonoscopy procedures requiring sedation. Prior to this amendment, Vice President Richard Nixon informally assumed some of President Dwight Eisenhower's duties for several weeks on each of three occasions when Eisenhower was ill.[20]

text: Informal roles[edit]

text: The extent of any informal roles and functions of the vice president depend on the specific relationship between the president and the vice president, but often include tasks such as drafter and spokesperson for the administration's policies, adviser to the president, and being a symbol of American concern or support. The influence of the vice president in this role depends almost entirely on the characteristics of the particular administration. Dick Cheney, for instance, was widely regarded as one of President George W. Bush's closest confidants. Al Gore was an important adviser to President Bill Clinton on matters of foreign policy and the environment. Often, vice presidents are chosen to act as a "balance" to the president, taking either more moderate or radical positions on issues.

text: Under the American system the president is both head of state and head of government, and the ceremonial duties of the former position are often delegated to the vice president. The vice president is often assigned the ceremonial duties of representing the president and the government at state funerals or other functions in the United States. This often is the most visible role of the vice president, and has occasionally been the subject of ridicule, such as during the vice presidency of George H. W. Bush. The vice president may meet with other heads of state or attend state funerals in other countries, at times when the administration wishes to demonstrate concern or support but cannot send the president personally.

text: Office as stepping stone to the presidency[edit]

text: In recent decades, the vice presidency has frequently been used as a platform to launch bids for the presidency. The transition of the office to its modern stature occurred primarily as a result of Franklin Roosevelt's 1940 nomination, when he captured the ability to nominate his running mate instead of leaving the nomination to the convention. Prior to that, party bosses often used the vice presidential nomination as a consolation prize for the party's minority faction. A further factor potentially contributing to the rise in prestige of the office was the adoption of presidential preference primaries in the early 20th century. By adopting primary voting, the field of candidates for vice president was expanded by both the increased quantity and quality of presidential candidates successful in some primaries, yet who ultimately failed to capture the presidential nomination at the convention.

text: Of the thirteen presidential elections from 1956 to 2004, nine featured the incumbent president; the other four (1960, 1968, 1988, 2000) all featured the incumbent vice president. Former vice presidents also ran, in 1984 (Walter Mondale), and in 1968 (Richard Nixon, against the incumbent vice president, Hubert Humphrey). The presidential election of 2008 was the first presidential election since 1928 that saw neither an incumbent president nor an incumbent or former vice president, take part in any primary or general election for the presidency on a major party ticket. Nixon is the only vice president to have been elected president while not an incumbent, as well as the only person elected twice to both the presidency and vice presidency.

text: Selection process[edit]

text: Eligibility[edit]

text: To be Constitutionally eligible to serve as the nation's vice president, a person must, according the 12th Amendment, meet the eligibility requirements to become president (which are stated in Article II, Section 1, Clause 5). Thus, to serve as vice president, an individual must:

text:
be a natural-born U.S. citizen;
be at least 35 years old;
be a resident in the U.S. for at least 14 years.[21]

text: A person who meets the above qualifications is still disqualified from holding the office of vice president under the following conditions:

text:
Under Article I, Section 3, Clause 7, upon conviction in impeachment cases, the Senate has the option of disqualifying convicted individuals from holding federal office, including that of vice president;
Under Section 3 of the Fourteenth Amendment, no person who has sworn an oath to support the Constitution, who has later has gone to war against the United States, or given aid and comfort to the nation's enemies can serve in a state or federal office – including as vice president. This disqualification, originally aimed at former supporters of the Confederacy, may be removed by a two-thirds vote of each house of the Congress.[22]

text: An additional disqualifying condition may exist under the Twenty-second Amendment, which limits the number of times as person may be elected president to no more than twice. Constitutional scholars disagree on whether a president who has already served two full terms is also ineligible to be elected or appointed vice president, as suggested by the Twelfth Amendment.[23][24] One viewpoint is that the 22nd Amendment's presidential term limit disqualifies any two-term president from later serving as vice president as well as from succeeding to the presidency from any point in the United States presidential line of succession. From another point of view, based on the literal language of the Constitution, a two-term former president could become vice president, as he or she is only barred from being elected president a third time, not from serving as president.[25] The practical applicability of this distinction has not been tested, as no former president has ever sought the vice presidency.

text: Residency limitation[edit]

text: While it is commonly held that the president and vice president must be residents of different states, this is not actually the case. Nothing in the Constitution prohibits both candidates being from a single state.

text: Instead, the limitation in the Twelfth Amendment imposed is on the members of the Electoral College, who must cast a ballot for at least one candidate who is not from their own state.

text: In theory, the candidates elected could both be from one state, but the electors of that state would, in a close electoral contest, run the risk of denying their vice presidential candidate the absolute majority required to secure the election, even if the presidential candidate is elected. This would then place the vice presidential election in the hands of the Senate.

text: In practice, however, residency is rarely an issue. Parties have avoided nominating tickets containing two candidates from the same state. Further, the candidates may themselves take action to alleviate any residency conflict. For example, at the start of the 2000 election cycle Dick Cheney was a resident of Texas; Cheney quickly changed his residency back to Wyoming, where he had previously served as a U.S. Representative, when Texas governor and Republican presidential nominee George W. Bush asked Cheney to be his vice presidential candidate.

text: Nominating process[edit]

text: Though the vice president does not need to have any political experience, most major-party vice presidential nominees are current or former United States Senators or Representatives, with the occasional nominee being a current or former Governor, a high-ranking military officer, or a holder of a major post within the Executive Department. The vice presidential candidates of the major national political parties are formally selected by each party's quadrennial nominating convention, following the selection of the party's presidential candidates. The official process is identical to the one by which the presidential candidates are chosen, with delegates placing the names of candidates into nomination, followed by a ballot in which candidates must receive a majority to secure the party's nomination.

text: In practice, the presidential nominee has considerable influence on the decision, and in the 20th century it became customary for that person to select a preferred running mate, who is then nominated and accepted by the convention. In recent years, with the presidential nomination usually being a foregone conclusion as the result of the primary process, the selection of a vice presidential candidate is often announced prior to the actual balloting for the presidential candidate, and sometimes before the beginning of the convention itself. The first presidential aspirant to announce his selection for vice president before the beginning of the convention was Ronald Reagan who, prior to the 1976 Republican National Convention announced that Richard Schweiker would be his running mate. Reagan's supporters then sought to amend the convention rules so that Gerald R. Ford would be required to name his vice presidential running mate in advance as well. The proposal was defeated, and Reagan did not receive the nomination in 1976. Often, the presidential nominee will name a vice presidential candidate who will bring geographic or ideological balance to the ticket or appeal to a particular constituency.

text: The vice presidential candidate might also be chosen on the basis of traits the presidential candidate is perceived to lack, or on the basis of name recognition. To foster party unity, popular runners-up in the presidential nomination process are commonly considered. While this selection process may enhance the chances of success for a national ticket, in the past it often insured that the vice presidential nominee represented regions, constituencies, or ideologies at odds with those of the presidential candidate. As a result, vice presidents were often excluded from the policy-making process of the new administration. Many times their relationships with the president and his staff were aloof, non-existent, or even adversarial.

text: The ultimate goal of vice presidential candidate selection is to help and not hurt the party's chances of getting elected, nonetheless several vice presidential selections have been controversial. In 1984, Democratic nominee Walter Mondale's groundbreaking choice of Geraldine Ferraro as his running mate (the first woman in U.S. history nominated for Vice President by a major political party), became a drag on the ticket due to repeated questions about her husband's finances. A selection whose positive traits make the presidential candidate look less favorable in comparison or which can cause the presidential candidate's judgment to be questioned often backfire, such as in 1988 when Democratic candidate Michael Dukakis chose experienced Texas Senator Lloyd Bentsen; Bentsen was considered a more seasoned statesman in federal politics and somewhat overshadowed Dukakis. Questions about Dan Quayle's experience were raised in the 1988 presidential campaign of George H. W. Bush, but the Bush-Quayle ticket still won handily. James Stockdale, the choice of third-party candidate Ross Perot in 1992, was seen as unqualified by many and Stockdale had little preparation for the vice presidential debate, but the Perot-Stockdale ticket still won about 19% of the vote. In 2008, Republican John McCain chose Sarah Palin as his running mate over his primary rivals and/or campaign surrogates such as Mitt Romney or Tom Ridge. This surprise move would, it was hoped, draw women voters disappointed by Hillary Clinton's defeat in the Democratic presidential primaries into the McCain camp. Palin's selection soon came to be seen as a negative for McCain, due to her several controversies during her gubernatorial tenure which were highlighted by the press, and her feuding with McCain campaign chairman Steve Schmidt. This perception continued to grow throughout the campaign, especially after her interviews with Katie Couric led to concerns about her fitness for the presidency.[26]

text: Historically, vice presidential candidates were chosen to provide geographic and ideological balance to a presidential ticket, widening a presidential candidate's appeal to voters from outside his regional base or wing of the party. Candidates from electoral-vote rich states were usually preferred. However, in 1992, moderate Democrat Bill Clinton (of Arkansas) chose moderate Democrat Al Gore (of Tennessee) as his running mate. Despite the two candidates' near-identical ideological and regional backgrounds, Gore's extensive experience in national affairs enhanced the appeal of a ticket headed by Clinton, whose political career had been spent entirely at the local and state levels of government. In 2000, George W. Bush chose Dick Cheney of Wyoming, a reliably Republican state with only three electoral votes, and in 2008, Barack Obama mirrored Bush's strategy when he chose Joe Biden of Delaware, a reliably Democratic state, likewise one with only three electoral votes. Both Cheney and Biden were chosen for their experience in national politics (experience lacked by both Bush and Obama) rather than the ideological balance or electoral vote advantage they would provide.

text: The first presidential candidate to choose his vice presidential candidate was Franklin D. Roosevelt in 1940.[27] The last not to name a vice presidential choice, leaving the matter up to the convention, was Democrat Adlai Stevenson in 1956. The convention chose Tennessee Senator Estes Kefauver over Massachusetts Senator (and later president) John F. Kennedy. At the tumultuous 1972 Democratic convention, presidential nominee George McGovern selected Senator Thomas Eagleton as his running mate, but numerous other candidates were either nominated from the floor or received votes during the balloting. Eagleton nevertheless received a majority of the votes and the nomination, though he later resigned from the ticket, resulting in Sargent Shriver becoming McGovern's final running mate; both lost to the Nixon-Agnew ticket by a wide margin, carrying only Massachusetts and the District of Columbia.

text: In cases where the presidential nomination is still in doubt as the convention approaches, the campaigns for the two positions may become intertwined. In 1976, Ronald Reagan, who was trailing President Gerald R. Ford in the presidential delegate count, announced prior to the Republican National Convention that, if nominated, he would select Senator Richard Schweiker as his running mate. This move backfired to a degree, as Schweiker's relatively liberal voting record alienated many of the more conservative delegates who were considering a challenge to party delegate selection rules to improve Reagan's chances. In the end, Ford narrowly won the presidential nomination and Reagan's selection of Schweiker became moot.

text: In the 2008 Democratic presidential primaries which pitted Hillary Clinton against Barack Obama, Clinton suggested a Clinton-Obama ticket with Obama in the vice president slot as it would be "unstoppable" against the presumptive Republican nominee. Obama rejected the offer outright saying "I want everybody to be absolutely clear. I'm not running for vice president. I'm running for president of the United States of America" while noting "With all due respect. I won twice as many states as Sen. Clinton. I've won more of the popular vote than Sen. Clinton. I have more delegates than Sen. Clinton. So, I don't know how somebody who's in second place is offering vice presidency to the person who's in first place". Obama stated that the nomination process would have to be a choice between himself and Clinton, saying "I don't want anybody here thinking that 'Somehow, maybe I can get both'", by nominating Clinton as president and assuming he would be her running mate".[28][29] Some suggested that it was a ploy by the Clinton campaign to denigrate Obama as less qualified for the presidency.[30] Later, when Obama became the presumptive Democratic nominee, former President Jimmy Carter cautioned against Clinton being picked for the vice president slot on the ticket, saying "I think it would be the worst mistake that could be made. That would just accumulate the negative aspects of both candidates", citing opinion polls showing 50% of US voters with a negative view of Hillary Clinton.[31]

text: Election[edit]

text: Vice presidents are elected indirectly in the United States. A number of electors, collectively known as the Electoral College, officially select the president and vice president. On Election Day, voters in each of the states and the District of Columbia cast ballots for these electors. Each state is allocated a number of electors, equal to the size of its delegation in both Houses of Congress combined. Generally, the ticket that wins the most votes in a state wins all of that state's electoral votes and thus has its slate of electors chosen to vote in the Electoral College.

text: The winning slate of electors meets at its state's capital on the first Monday after the second Wednesday in December, about six weeks after the election, to vote. They then send a record of that vote to Congress. The vote of the electors is opened by the sitting vice president, acting in his capacity as President of the Senate and read aloud to a joint session of the incoming Congress, which was elected at the same time as the president and vice president.

text: Oath and tenure[edit]

text: Pursuant to the Twentieth Amendment, the vice president's term of office begins at noon on January 20 of the year following the election. This date, known as Inauguration Day, marks the beginning of the four-year terms of both the president and vice president.

text: Although Article VI requires that the vice president take an oath or affirmation of allegiance to the US Constitution, unlike the president, the United States Constitution does not specify the precise wording of the oath of office for the vice president. Several variants of the oath have been used since 1789; the current form, which is also recited by Senators, Representatives and other government officers, has been used since 1884:

text: I, (first name last name), do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God.[32][33]

text: The term of office for vice president is four years. While the Twenty-Second Amendment generally restricts the president to two terms, there is no such limitation on the office of vice president, meaning an eligible person could hold the office as long as voters continued to vote for electors who in turn would reelect the person to the office. Additionally, a vice president could even serve under different presidents. This has happened twice: George Clinton (1805–1812) served under both Thomas Jefferson and James Madison; and John C. Calhoun (1825–1832) served under John Quincy Adams and Andrew Jackson.[4]

text: Original election process and reform[edit]

text: Under the original terms of the Constitution (Article II, Section 1, Clause 3), the electors of the Electoral College voted only for office of president rather than for both president and vice president. Each elector was allowed to vote for two people for the top office; and could not differentiate between their first and second choice for the presidency. The person receiving the greatest number of votes (provided that such a number was a majority of electors) would be president, while the individual who received the next largest number of votes became vice president. If no one received a majority of votes, then the president and vice president would be elected by means of a Contingent election. The House of Representatives would choose among the five candidates with the largest numbers of votes, with each state's representatives together casting a single vote. In such a case, the person who received the highest number of votes but was not chosen president would become vice president. In the case of a tie for second, then the Senate would choose the vice president.[34]

text: The emergence of political parties and nationally coordinated election campaigns during the 1790s (which the Constitution's framers had not contemplated) soon frustrated this original plan. In the election of 1796, Federalist John Adams came in first, but because the Federalist electors had divided their second vote amongst several vice presidential candidates, Democratic-Republican Thomas Jefferson came second. Thus, the president and vice president were from opposing parties. Conflict between the two arose early on over the increasingly turbulent relations between the U.S. and France. Ultimately, Jefferson became more an "opposition leader", and actively sought to frustrate the president's policies. Then, in the election of 1800, Democratic-Republican electors (for reasons that are disputed), though clearly preferring Jefferson over Aaron Burr, the party's secondary candidate, sought to guarantee that their party won both offices, and cast 37 electoral votes for both Jefferson and Burr. In the contingent election that followed, Jefferson finally won on the 36th ballot, and Burr became vice president.[35]

text: This hardening of party lines and resultant straight-ticket voting practices led to the adoption of the Twelfth Amendment in 1804, which directs electors to use separate ballots to vote for the president and vice president.[35] While this solved the problems that had arisen under the previous system, it ultimately had the effect of lowering the prestige of the vice presidency, as the office was no longer for the leading challenger for the presidency. The amendment also prescribes that, if no vice presidential candidate receives an Electoral College majority, then the Senate selects the vice president, with a majority vote of the entire membership (currently 51 of 100 senators, assuming there are no vacancies) being necessary for election.[36] There has been only one such contingent election since the 12th Amendment was ratified. It occurred on February 8, 1837, when no candidate for the vice presidency received a majority of electoral votes in the 1836 election. By a 33-17 vote, Richard Mentor Johnson (Martin Van Buren's running mate) was elected the nation's ninth vice president.[37]

text: Salary[edit]

text: The vice president's salary is $230,700.[38] The salary was set by the 1989 Government Salary Reform Act, which also provides an automatic cost of living adjustment for federal employees. The vice president does not automatically receive a pension based on that office, but instead receives the same pension as other members of Congress based on his position as President of the Senate.[39] The vice president must serve a minimum of two years to qualify for a pension.[40]

text: Since 1974, the official residence of the vice president and their family has been Number One Observatory Circle, on the grounds of the United States Naval Observatory in Washington, D.C.

text: Impeachment[edit]

text: Article I, Section 2, Clause 5 and Article II, Section 4 of the Constitution both authorize the House of Representatives to serve as a "grand jury" with the power to impeach high federal officials, including the vice president, for "treason, bribery, or other high crimes and misdemeanors." Similarly, Article I, Section 3, Clause 6 and Article II, Section 4 both authorize the Senate to serve as a court with the power to remove impeached officials from office, given a two-thirds vote to convict. No vice president has ever been impeached.

text: Vacancies[edit]

text: Prior to ratification of the Twenty-fifth Amendment in 1967, no constitutional provision existed for filling an intra-term vacancy in the vice presidency. As a result, when one occurred, the office was left vacant until filled through the next ensuing election and inauguration. Between 1812 and 1967, the vice presidency was vacant on sixteen occasions—as a result of seven deaths,[41] one resignation, and eight cases in which the vice president succeeded to the presidency.

text: Section 2 of the Twenty-fifth Amendment established a procedure for filling such a vacancy.

text: Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress.

text: Since it came into force the office has been vacant twice, until the confirmation of a new vice president by both houses of Congress and the swearing in ceremony. The first such instance occurred in 1973 following the resignation of Spiro Agnew, Richard Nixon's vice president. Gerald Ford was subsequently nominated by President Nixon and confirmed by Congress. The second occurred 10 months later when Nixon resigned following the Watergate scandal and Ford assumed the presidency. The resulting vice presidential vacancy was filled by Nelson Rockefeller.[20][41] Ford and Rockefeller are the only two people to have served as vice president without having been elected to the office, and Ford remains the only person to have served as both vice president and president without being elected to either office.

text:
Vice Presidency vacancies[4]

Dates
Length
in days
Reason
Next Vice President
after vacancy

01 !March 4, 1789 – April 21, 1789
7001480000000000000♠48
Logistical delays as the new Federal Government began operations
John Adams, following his inauguration

02 !April 20, 1812 – March 4, 1813
7002318000000000000♠318
George Clinton died
Elbridge Gerry, following election of 1812

03 !November 23, 1814 – March 4, 1817
7002832000000000000♠832
Elbridge Gerry died
Daniel D. Tompkins, following election of 1816

04 !December 28, 1832 – March 4, 1833
7001660000000000000♠66
John C. Calhoun resigned
Martin Van Buren, following election of 1832

05 !April 4, 1841 – March 4, 1845
7003143000000000000♠1,430
John Tyler succeeded to presidency
George M. Dallas, following election of 1844

06 !July 9, 1850 – March 4, 1853
7002969000000000000♠969
Millard Fillmore succeeded to presidency
William R. King, following election of 1852

07 !April 18, 1853 – March 4, 1857
7003141600000000000♠1,416
William R. King died
John C. Breckinridge, following election of 1856

08 !April 15, 1865 – March 4, 1869
7003141900000000000♠1,419
Andrew Johnson succeeded to presidency
Schuyler Colfax, following election of 1868

09 !November 22, 1875 – March 4, 1877
7002468000000000000♠468
Henry Wilson died
William A. Wheeler, following election of 1876

10 !September 19, 1881 – March 4, 1885
7003126200000000000♠1,262
Chester A. Arthur succeeded to presidency
Thomas A. Hendricks, following election of 1884

11 !November 25, 1885 – March 4, 1889
7003119500000000000♠1,195
Thomas A. Hendricks died
Levi P. Morton, following election of 1888

12 !November 21, 1899 – March 4, 1901
7002468000000000000♠468
Garret Hobart died
Theodore Roosevelt, following election of 1900

13 !September 14, 1901 – March 4, 1905
7003126700000000000♠1,267
Theodore Roosevelt succeeded to presidency
Charles W. Fairbanks, following election of 1904

14 !October 30, 1912 – March 4, 1913
7002125000000000000♠125
James S. Sherman died
Thomas R. Marshall, following election of 1912

15 !August 2, 1923 – March 4, 1925
7002580000000000000♠580
Calvin Coolidge succeeded to presidency
Charles G. Dawes, following election of 1924

16 !April 12, 1945 – January 20, 1949
7003137900000000000♠1,379
Harry S. Truman succeeded to presidency
Alben W. Barkley, following election of 1948

17 !November 22, 1963 – January 20, 1965
7002425000000000000♠425
Lyndon B. Johnson succeeded to presidency
Hubert Humphrey, following election of 1964

18 !October 10, 1973 – December 6, 1973
7001570000000000000♠57
Spiro Agnew resigned
Gerald Ford, following confirmation by Congress

19 !August 9, 1974 – December 19, 1974
7002132000000000000♠132
Gerald Ford succeeded to presidency
Nelson Rockefeller, following confirmation by Congress

text: Growth of the office[edit]

text: For much of its existence, the office of vice president was seen as little more than a minor position. John Adams, the first vice president, was the first of many frustrated by the "complete insignificance" of the office. To his wife Abigail Adams wrote, "My country has in its wisdom contrived for me the most insignificant office that ever the invention of man . . . or his imagination contrived or his imagination conceived; and as I can do neither good nor evil, I must be borne away by others and met the common fate."[42] John Nance Garner, who served as vice president from 1933 to 1941 under President Franklin D. Roosevelt, claimed that the vice presidency "isn't worth a pitcher of warm piss."[43] Harry Truman, who also served as vice president under Roosevelt, said that the office was as "useful as a cow's fifth teat."[44]

text: Thomas R. Marshall, the 28th vice president, lamented: "Once there were two brothers. One ran away to sea; the other was elected Vice President of the United States. And nothing was heard of either of them again."[45] His successor, Calvin Coolidge, was so obscure that Major League Baseball sent him free passes that misspelled his name, and a fire marshal failed to recognize him when Coolidge's Washington residence was evacuated.[46]

text: When the Whig Party asked Daniel Webster to run for the vice presidency on Zachary Taylor's ticket, he replied "I do not propose to be buried until I am really dead and in my coffin."[47] This was the second time Webster declined the office, which William Henry Harrison had first offered to him. Ironically, both of the presidents making the offer to Webster died in office, meaning the three-time presidential candidate could have become president if he had accepted either. Since presidents rarely died in office, however, the better preparation for the presidency was considered to be the office of Secretary of State, in which Webster served under Harrison, Tyler, and later, Taylor's successor, Fillmore.

text: In the first 100 years of the United States no fewer than seven proposals to amend the constitution to abolish the office of Vice President were advanced in the United States Congress.[48] The first such amendment was presented by Samuel W. Dana in 1800 and was defeated by a vote of 27 to 85 in the United States House of Representatives.[48] A second proposed amendment, introduced by United States Senator James Hillhouse in 1808 was also defeated.[48] During the late-1860s and 1870s, five additional amendments were proposed.[48] One supporter of the proposals, James Mitchell Ashley , opined that the office of Vice President was "superfluous" and dangerous.[48]

text: Garret Hobart, the first vice president under William McKinley, was one of the very few vice presidents at this time who played an important role in the administration. A close confidant and adviser of the president, Hobart was called "Assistant President."[49] However, until 1919, vice presidents were not included in meetings of the President's Cabinet. This precedent was broken by President Woodrow Wilson when he asked Thomas R. Marshall to preside over Cabinet meetings while Wilson was in France negotiating the Treaty of Versailles.[50] President Warren G. Harding also invited his vice president, Calvin Coolidge, to meetings. The next vice president, Charles G. Dawes, did not seek to attend Cabinet meetings under President Coolidge, declaring that "the precedent might prove injurious to the country."[51] Vice President Charles Curtis was also precluded from attending by President Herbert Hoover.

text: In 1933, Franklin D. Roosevelt raised the stature of the office by renewing the practice of inviting the vice president to cabinet meetings, which every president since has maintained. Roosevelt's first vice president, John Nance Garner, broke with him over the "court-packing issue, early in his second term, and became Roosevelt's leading critic. At the start of that term, on January 20, 1937, Garner had been the first Vice President to be sworn into office on the Capitol steps in the same ceremony with the president; a tradition that continues. Prior to that time, vice presidents were traditionally inaugurated at a separate ceremony in the Senate chamber. Gerald R. Ford and Nelson A. Rockefeller, who were both appointed to the office under the terms of the 25th amendment, were inaugurated in the House and Senate chambers, respectively.

text: Henry Wallace, Roosevelt's Vice President during his third term (1941–1945), was given major responsibilities during World War II. However, after numerous policy disputes between Wallace and other Roosevelt Administration and Democratic Party officials, he was denied renomination to office at the 1944 Democratic National Convention. Harry Truman was selected instead. During his 82 day vice presidency, Truman was not informed about any war or post-war plans, including the Manhattan Project, leading Truman to remark, wryly, that the job of the Vice President was to "go to weddings and funerals." As a result of this experience, Truman, after succeeding to the presidency upon Roosevelt's death, recognized the need to keep the Vice President informed on national security issues. Congress made the vice president one of four statutory members of the National Security Council in 1949.

text: The stature of the Vice-presidency grew again while Richard Nixon was in office (1953–1961). He attracted the attention of the media and the Republican party, when Dwight Eisenhower authorized him to preside at Cabinet meetings in his absence. Nixon was also the first vice president to formally assume temporary control of the executive branch, which he did after Eisenhower suffered a heart attack on September 24, 1955, ileitis in June 1956, and a stroke in November 1957.

text: Until 1961, vice presidents had their offices on Capitol Hill, a formal office in the Capitol itself and a working office in the Russell Senate Office Building. Lyndon B. Johnson was the first vice president to be given an office in the White House complex, in the Old Executive Office Building. The former Navy Secretary's office in the OEOB has since been designated the "Ceremonial Office of the Vice President" and is today used for formal events and press interviews. President Jimmy Carter was the first president to give his vice president, Walter Mondale, an office in the West Wing of the White House, which all vice presidents have since retained. Because of their function as Presidents of the Senate, vice presidents still maintain offices and staff members on Capitol Hill.

text: Though Walter Mondale's tenure was the beginning of the modern day power of the vice presidency, the tenure of Dick Cheney saw a rapid growth in the office of the vice president. Vice President Cheney held a tremendous amount of power and frequently made policy decisions on his own, without the knowledge of the President.[52] After his tenure, and during the 2008 presidential campaign, both vice presidential candidates, Sarah Palin and Joe Biden, stated the office had expanded too much under Cheney's tenure and both claimed they would reduce the role to simply being an adviser to the president.[53] This rapid growth has led to calls for abolition of the vice presidency from various constitutional scholars and political commentators such as: Arthur M. Schlesinger Jr., Matthew Yglesias, and Bruce Ackerman.[54][55][56]

text: Post–vice presidency[edit]

text: This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2017) (Learn how and when to remove this template message)

text: Four vice presidents have been elected to the presidency while serving as vice president: John Adams, Thomas Jefferson, Martin Van Buren and George H. W. Bush. Additionally, John C. Breckinridge, Richard Nixon, Hubert Humphrey and Al Gore were each nominated by their respective parties, but did not succeed the presidents with whom they were elected, though Nixon was elected president eight years later.

text: Two former vice presidents unsuccessfully sought a non-conconsecutive term in office:

text:
Adlai Stevenson I, vice president under Grover Cleveland, in 1900, as William Jennings Bryan's running mate.
Charles W. Fairbanks, vice president under Theodore Roosevelt, in 1916, as Charles Evans Hughes' running mate.

text: One vice president sought the office unsuccessfully, but was later elected to it:

text: Thomas A. Hendricks ran in 1876 as the running mate of Democratic nominee Samuel J. Tilden. Eight years later, he was elected vice president as the running mate of Grover Cleveland.

text: Several former vice presidents have sought other offices after serving as vice president:

text:
Daniel D. Tompkins ran for Governor of New York in 1820 while serving as vice president under James Monroe. He lost to DeWitt Clinton, but was re-elected vice president.
John C. Calhoun resigned as vice president to accept election as US Senator from South Carolina.
Hannibal Hamlin, Andrew Johnson, Alben Barkley and Hubert H. Humphrey were all elected to the Senate after leaving office.
Levi P. Morton, vice president under Benjamin Harrison, was elected Governor of New York after leaving office.
Adlai Stevenson I was narrowly defeated for Governor of Illinois in 1908.
Richard Nixon unsuccessfully sought the governorship of California in 1962, nearly two years after leaving office as vice president and just over six years before becoming president.
Walter Mondale ran unsuccessfully for president in 1984, served as U.S. Ambassador to Japan from 1993 to 1996, and then sought unsuccessfully to return to the Senate in 2002.
George H. W. Bush's vice president, Dan Quayle, unsuccessfully sought the Republican nomination in 2000.

text: Since 1977, former presidents and vice presidents who are elected or re-elected to the Senate are entitled to the largely honorific position of Deputy President pro tempore. So far, the only former vice president to have held this title is Hubert Humphrey following his return to the Senate. Walter Mondale would have been entitled to the position had his 2002 Senate bid been successful.

text: Under the terms of an 1886 Senate resolution, all former vice presidents are entitled to a portrait bust in the Senate wing of the United States Capitol, commemorating their service as presidents of the Senate. Dick Cheney is the most recent former vice president to be so honored.

text: Unlike former presidents, who receive a pension automatically regardless of their time in office, former vice presidents must reach pension eligibility by accumulating the appropriate time in federal service. Since 2008, former vice presidents are also entitled to Secret Service personal protection.[57] Former vice presidents traditionally receive Secret Service protection for up to six months after leaving office, by order of the Secretary of Homeland Security, though this can be extended if the Secretary believes the level of threat is sufficient.[58]

text: In 2008, a bill titled the "Former Vice President Protection Act" was passed by Congress and signed into law by President Bush.[59] It provides six-month Secret Service protection by law to a former vice president and family. According to the Department of Homeland Security, protection for former vice president Cheney has been extended numerous times because threats against him have not decreased since his leaving office.[60]

text: Timeline of vice presidents[edit]

text: This is a graphical timeline listing of the Vice Presidents of the United States.


document_title: Spanning Tree Protocol

question_text: which are the port roles in stp protocol

root

text: Spanning Tree Protocol

text: Protocol operation[edit]

text: The need for the Spanning Tree Protocol (STP) arose because switches in local area networks (LANs) were often interconnected using redundant links to improve resilience should one connection, called a link, fail. However, this was found to create transmission loops, broadcast storms and MAC address table trashing. If redundant links are used to connect switches, then transmission loops need to be avoided[4] because data link layer 2 Ethernet frames do not expire. Potentially an Ethernet frame with a destination MAC address that is not in the MAC address table of the immediate switch can be bounced around between switches in the local area network. Redundant links between these switches could result in the Ethernet frame never reaching a Switch that has the destination MAC address in its MAC address table. In such cases switches also broadcast the Ethernet frames to all ports, except the one from which it entered. This can create a broadcast storm. However, if only one link between switches exists, entire segments of the local area network would become unavailable should this one link fail. Thus it has become best practice to establish a second redundant link between critical switches.[5] If more than one link between two switches are used to transmit Ethernet frames, a switch will receive Ethernet frames with the same source MAC address through two ports, resulting in what is known as MAC address table trashing.[6]

tag: p

text: To avoid the problems associated with redundant links in a switched LAN, the Spanning Tree Protocol (STP) is implemented on switches to monitor the network topology. Every link between switches, and in particular redundant links, are catalogued. STP then disables redundant links by setting up one preferred and optimized link between switches in the LAN. This preferred link is used for all Ethernet frames unless it fails, in which case the non-preferred redundant link is enabled. When implemented in a network, STP designates one layer 2 switch as root bridge. On this root bridge the preferred and non-preferred links are calculated. The root bridge switch constantly communicates with the other switches in the LAN that implement STP, called non-root bridges, using Bridge Protocol Data Units (BPDUs).[6]

text:
Data rate

STP cost

RSTP cost[7]:154

(Link Bandwidth)

(802.1D-1998)

(802.1W-2004, default value)

4 Mbit/s

250

5,000,000

10 Mbit/s

100

2,000,000

16 Mbit/s

62

1,250,000

100 Mbit/s

19

200,000

1 Gbit/s

4

20,000

2 Gbit/s

3

10,000

10 Gbit/s

2

2,000

100 Gbit/s

N/A

200

1 Tbit/s

N/A

20

tag: table

text: Provided there is more than one link between two switches, the STP root bridge calculates the cost of each path based on bandwidth. STP will select the path with the lowest cost, that is the highest bandwidth, as the preferred link. STP will enable this preferred link as the only path to be used for Ethernet frames between the two switches, and disable all other possible links by designating the switch ports that connect the preferred path as root port.[8] The STP path cost default was originally calculated by the formula 1 Gigabit / second/bandwidth. When faster speeds became available, the default values were adjusted as otherwise speeds above 1 Gbit/s would have been indistinguishable by STP. Its successor RSTP uses a similar formula with a larger numerator: 20 Terabit / second/bandwidth. These formulas lead to the sample values in the table on the right:[7]:154

text: After STP enabled switches in a LAN have elected the root bridge, all non-root bridges assign one of their ports as root port. This is either the port that connects the switch to the root bridge, or if there are several paths, the port with the preferred path as calculated by the root bridge. Because not all switches are directly connected to the root bridge they communicate amongst each other using STP Bridge Protocol Data Units (BPDUs). Each switch adds the cost of its own path to the cost received from the neighboring switches to determine the total cost of a given path to the root bridge. Once the cost of all possible paths to the root bridge have been added up, each switch assigns a port as root port which connects to the path with the lowest cost, or highest bandwidth, that will eventually lead to the root bridge.[9]

text: STP switch port states[edit]

text: All switch ports in the LAN where STP is enabled are categorized.[6]

text:
Blocking - A port that would cause a switching loop if it were active.  No user data is sent or received over a blocking port, but it may go into forwarding mode if the other links in use fail and the spanning tree algorithm determines the port may transition to the forwarding state. BPDU data is still received in blocking state. Prevents the use of looped paths.
Listening - The switch processes BPDUs and awaits possible new information that would cause it to return to the blocking state. It does not populate the MAC address table and it does not forward frames.
Learning - While the port does not yet forward frames it does learn source addresses from frames received and adds them to the filtering database (switching database). It populates the MAC address table, but does not forward frames.
Forwarding - A port receiving and sending data in Ethernet frames, normal operation. The Forwarding port monitors incoming BPDUs that would indicate it should return to the blocking state to prevent a loop.
Disabled - A network administrator has manually disabled a switch port

tag: ul

text: When a device is first attached to a switch port, it will not immediately start to forward data. It will instead go through a number of states while it processes BPDUs and determines the topology of the network. When a host is attached, such as a computer, printer or server, the port always goes into the forwarding state, albeit after a delay of about 30 seconds while it goes through the listening and learning states (see below). The time spent in the listening and learning states is determined by a value known as the forward delay (default 15 seconds and set by the root bridge). However, if instead another switch is connected, the port may remain in blocking mode if it is determined that it would cause a loop in the network. Topology Change Notification (TCN) BPDUs are used to inform other switches of port changes. TCNs are injected into the network by a non-root switch and propagated to the root. Upon receipt of the TCN, the root switch will set a Topology Change flag in its normal BPDUs. This flag is propagated to all other switches to instruct them to rapidly age out their forwarding table entries.

text: Configuring a spanning tree[edit]

text: Configuring STP and RSTP on switches in a LAN follows the same principles. STP must be enabled on all switches in the LAN and the version of STP must be chosen. All switches must use the same version of STP. Then the administrator must determine which switch will be the root bridge, and the priority of the other switches in the spanning tree. If the root bridge goes down, the protocol will automatically assign a new root bridge based on the bridge ID. If all switches have the same bridge ID, such as the default ID, and the root bridge goes down, a tie situation arises and the protocol will assign one switch as root bridge based on the switch MAC addresses. Once the switches have been assigned a bridge ID and the protocol has chosen the root bridge switch, the best path to the root bridge is calculated based on port cost, path cost and port priority.[10] Ultimately STP calculates the path cost on the basis of the bandwidth of a link, however links between switches may have the same bandwidth. Administrators can influence the protocol's choice of the preferred path by configuring the port cost, the lower the port cost the more likely it is that the protocol will choose the connected link as root port for the preferred path.[11] Before the bridge ID or the port costs are configured, the network topology should be carefully planned.[12] The selection of how other switches in the topology choose their root port, or the least cost path to the root bridge, can be influenced by the port priority. The highest priority will mean the path will ultimately be less preferred. If all ports of a switch have the same priority, the port with the lowest number is chosen to forward frames.[13]

text: Select a root bridge and the bridge ID[edit]

text: The root bridge of the spanning tree is the bridge with the smallest (lowest) bridge ID. Each bridge has a configurable priority number and a MAC address; the bridge ID is the concatenation of the bridge priority and the MAC address. For example, the ID of a bridge with priority 32768 and mac 0200.0000.1111 is 32768.0200.0000.1111. The bridge priority default is 32768 and can only be configured in multiples of 4096.[a] When comparing two bridge IDs, the priority portions are compared first and the MAC addresses are compared only if the priorities are equal. The switch with the lowest priority of all the switches will be the root; if there is a tie, then the switch with the lowest priority and lowest MAC address will be the root. For example, if switches A (MAC=0200.0000.1111) and B (MAC=0200.0000.2222) both have a priority of 32768 then switch A will be selected as the root bridge.[b] If the network administrators would like switch B to become the root bridge, they must set its priority to be less than 32768.[c]

text: Protocol choice of the path to the root bridge[edit]

text: The sequence of events to determine the best received BPDU (which is the best path to the root) is:

text:
Lowest root bridge ID - Determines the root bridge
Lowest cost to the root bridge - Favors the upstream switch with the least cost to root
Lowest sender bridge ID - Serves as a tie breaker if multiple upstream switches have equal cost to root
Lowest sender port ID - Serves as a tie breaker if a switch has multiple (non-Etherchannel) links to a single upstream switch, where:
Bridge ID = priority (4 bits) + locally assigned system ID extension (12 bits) + ID [MAC address] (48 bits); the default bridge priority is 32768, and
Port ID = priority (4 bits) + ID (Interface number) (12 bits); the default port priority is 128.

text: Breaking ties in selecting the path to the root bridge[edit]

text: Breaking ties for root ports: When multiple paths from a bridge are least-cost paths, the chosen path uses the neighbor bridge with the lower bridge ID. The root port is thus the one connecting to the bridge with the lowest bridge ID. For example, in figure 3, if switch 4 were connected to network segment d instead of segment f, there would be two paths of length 2 to the root, one path going through bridge 24 and the other through bridge 92. Because there are two least cost paths, the lower bridge ID (24) would be used as the tie-breaker in choosing which path to use.

text: Breaking ties for designated ports: When the root bridge has more than one port on a single LAN segment, the bridge ID is effectively tied, as are all root path costs (all equal zero). The designated port then becomes the port on that LAN segment with the lowest port ID. It's put into Forwarding mode while all other ports on the root bridge on that same LAN segment become non-designated ports and are put into blocking mode.[14] Not all bridge/switch manufacturers follow this rule, instead making all root bridge ports designated ports, and putting them all in forwarding mode. A final tie-breaker is required as noted in the section "The final tie-breaker."

text: When more than one bridge on a segment leads to a least-cost path to the root, the bridge with the lower bridge ID is used to forward messages to the root. The port attaching that bridge to the network segment is the designated port for the segment. In the diagram on the right there are two least cost paths from network segment d to the root, one going through bridge 24 and the other through bridge 92. The lower bridge ID is 24, so the tie breaker dictates that the designated port is the port through which network segment d is connected to bridge 24. If bridge IDs were equal, then the bridge with the lowest MAC address would have the designated port. In either case, the loser sets the port as being blocked.

text: The final tie-breaker.  In some cases, there may still be a tie, as when the root bridge has multiple active ports on the same LAN segment (see above, "Breaking ties for designated ports") with equally low root path costs and bridge IDs, or, in other cases, multiple bridges are connected by multiple cables and multiple ports. In each case, a single bridge may have multiple candidates for its root port. In these cases, candidates for the root port have already received BPDUs offering equally-low (i.e. the "best") root path costs and equally-low (i.e. the "best") bridge IDs, and the final tie breaker goes to the port that received the lowest (i.e. the "best") port priority ID, or port ID.[15]

text: Bridge Protocol Data Units[edit]

text: The above rules describe one way of determining what spanning tree will be computed by the algorithm, but the rules as written require knowledge of the entire network. The bridges have to determine the root bridge and compute the port roles (root, designated, or blocked) with only the information that they have. To ensure that each bridge has enough information, the bridges use special data frames called Bridge Protocol Data Units (BPDUs) to exchange information about bridge IDs and root path costs.

text: A bridge sends a BPDU frame using the unique MAC address of the port itself as a source address, and a destination address of the STP multicast address 01:80:C2:00:00:00.

text: There are two types of BPDUs in the original STP specification[7]:63 (the Rapid Spanning Tree (RSTP) extension uses a specific RSTP BPDU):

text:
Configuration BPDU (CBPDU), used for Spanning Tree computation
Topology Change Notification (TCN) BPDU, used to announce changes in the network topology

text: BPDUs are exchanged regularly (every 2 seconds by default) and enable switches to keep track of network changes and to start and stop forwarding at ports as required. To prevent the delay when connecting hosts to a switch and during some topology changes, Rapid STP was developed, which allows a switch port to rapidly transition into the forwarding state during these situations.

text: Bridge Protocol Data Unit fields[edit]

text: IEEE 802.1D and IEEE 802.1aq BPDUs have the following format:

text: Spanning Tree Protocol standards[edit]

text: The first spanning tree protocol was invented in 1985 at the Digital Equipment Corporation by Radia Perlman.[1] In 1990, the IEEE published the first standard for the protocol as 802.1D,[16] based on the algorithm designed by Perlman. Subsequent versions were published in 1998[17] and 2004,[18] incorporating various extensions. The original Perlman-inspired Spanning Tree Protocol, called DEC STP, is not a standard and differs from the IEEE version in message format as well as timer settings. Some bridges implement both the IEEE and the DEC versions of the Spanning Tree Protocol, but their interworking can create issues for the network administrator, as illustrated by the problem discussed in an on-line Cisco document.[19]

text: Different implementations of a standard are not guaranteed to work, due for example to differences in default timer settings. The IEEE encourages vendors to provide a "Protocol Implementation Conformance Statement", declaring which capabilities and options have been implemented,[18] to help users determine whether different implementations will interwork correctly.

text: Rapid Spanning Tree Protocol[edit]

text: In 2001, the IEEE introduced Rapid Spanning Tree Protocol (RSTP) as 802.1w.  RSTP provides significantly faster spanning tree convergence after a topology change, introducing new convergence behaviors and bridge port roles to do this.  RSTP was designed to be backwards-compatible with standard STP.

text: While STP can take 30 to 50 seconds to respond to a topology change, RSTP is typically able to respond to changes within 3 × Hello times (default: 3 times 2 seconds) or within a few milliseconds of a physical link failure. The Hello time is an important and configurable time interval that is used by RSTP for several purposes; its default value is 2 seconds.[20][21]

text: Standard IEEE 802.1D-2004 incorporates RSTP and obsoletes the original STP standard.[22]

text: Rapid Spanning Tree Operation[edit]

text: RSTP adds new bridge port roles in order to speed convergence following a link failure. The number of states a port can be in has been reduced to three instead of STP's original five.

text: RSTP bridge port roles:

text:
Root - A forwarding port that is the best port from non-root bridge to root bridge
Designated - A forwarding port for every LAN segment
Alternate - An alternate path to the root bridge. This path is different from using the root port
Backup - A backup/redundant path to a segment where another bridge port already connects
Disabled - Not strictly part of STP, a network administrator can manually disable a port

text: RSTP switch port states:

text:
Discarding - No user data is sent over the port
Learning - The port is not forwarding frames yet, but is populating its MAC-address-table
Forwarding - The port is fully operational

text: RSTP operational details:

text:
Detection of root switch failure is done in 3 hello times, which is 6 seconds if the default hello times have not been changed.
Ports may be configured as edge ports if they are attached to a LAN that has no other bridges attached. These edge ports transition directly to the forwarding state. RSTP still continues to monitor the port for BPDUs in case a bridge is connected. RSTP can also be configured to automatically detect edge ports. As soon as the bridge detects a BPDU coming to an edge port, the port becomes a non-edge port.
RSTP calls the connection between two or more switches as a "link-type" connection. A port that operates in full-duplex mode is assumed to be point-to-point link, whereas a half-duplex port (through a hub) is considered a shared port by default. This automatic link type setting can be overridden by explicit configuration. RSTP improves convergence on point-to-point links by reducing the Max-Age time to 3 times Hello interval, removing the STP listening state, and exchanging a handshake between two switches to quickly transition the port to forwarding state. RSTP does not do anything differently from STP on shared links.
Unlike in STP, RSTP will respond to BPDUs sent from the direction of the root bridge. An RSTP bridge will "propose" its spanning tree information to its designated ports. If another RSTP bridge receives this information and determines this is the superior root information, it sets all its other ports to discarding. The bridge may send an "agreement" to the first bridge confirming its superior spanning tree information. The first bridge, upon receiving this agreement, knows it can rapidly transition that port to the forwarding state bypassing the traditional listening/learning state transition. This essentially creates a cascading effect away from the root bridge where each designated bridge proposes to its neighbors to determine if it can make a rapid transition. This is one of the major elements that allows RSTP to achieve faster convergence times than STP.
As discussed in the port role details above, RSTP maintains backup details regarding the discarding status of ports. This avoids timeouts if the current forwarding ports were to fail or BPDUs were not received on the root port in a certain interval.
RSTP will revert to legacy STP on an interface if a legacy version of an STP BPDU is detected on that port.

text: Spanning Tree Protocol standards for VLANs[edit]

text: STP and RSTP do not segregate switch ports by VLAN.[23] However, in Ethernet switched environments where multiple Virtual LANs (VLANs) exist, it is often desirable to create multiple spanning trees so that traffic from different VLANs uses different links.

text: Proprietary Spanning Tree VLAN standards[edit]

text: Before the IEEE published a Spanning Tree Protocol standard for VLANs a number of vendors who sold VLAN capable switches developed their own Spanning Tree Protocol versions that were VLAN capable. Cisco developed, implemented and published the Per-VLAN Spanning Tree (PVST) proprietary protocol using its own proprietary Inter-Switch Link (ISL) for VLAN encapsulation, and PVST+ which uses 802.1Q VLAN encapsulation. Both standards implement a separate spanning tree for every VLAN. Cisco switches now commonly implement PVST+ and can only implement Spanning Trees for VLANs if the other switches in the LAN implement the same VLAN STP protocol. Very few switches from other vendors support Cisco's various proprietary protocols. HP provides PVST and PVST+ compatibility in some of its network switches.[24] Some devices from Force10 Networks, Alcatel-Lucent, Extreme Networks, Avaya, Brocade Communications Systems and BLADE Network Technologies support PVST+.[25][26][27] Extreme Networks does so with two limitations: Lack of support on ports where the VLAN is untagged/native, and also on the VLAN with ID 1. PVST+ can tunnel across an MSTP Region.[28]

text: The switch vendor Juniper Networks in turn developed and implemented its VLAN Spanning Tree Protocol (VSTP) to provide compatibility with Cisco's PVST, so that the switches from both vendors can be included in one LAN.[23] The VSTP protocol is only supported by the EX and MX Series from Juniper Networks. There are two restrictions to the compatibility of VSTP:

text:
VSTP supports only 253 different spanning-tree topologies. If there are more than 253 VLANs, it is recommended to configure RSTP in addition to VSTP, and VLANs beyond 253 will be handled by RSTP.
MVRP does not support VSTP. If this protocol is in use, VLAN membership for trunk interfaces must be statically configured [1].

tag: ol

text: By default, VSTP uses the RSTP protocol as its core spanning-tree protocol, but usage of STP can be forced if the network includes old bridges [2]. More information about configuring VSTP on Juniper Networks switches was published in the official documentation Understanding VSTP.

text: Cisco also published a proprietary version of Rapid Spanning Tree Protocol. It creates a spanning tree for each VLAN, just like PVST. Cisco refers to this as Rapid Per-VLAN Spanning Tree (RPVST).

text: Multiple Spanning Tree Protocol[edit]

text: The Multiple Spanning Tree Protocol (MSTP), originally defined in IEEE 802.1s and later merged into IEEE 802.1Q-2005, defines an extension to RSTP to further develop the usefulness of virtual LANs (VLANs).

text: In the standard a spanning tree that maps one or more VLANs is called multiple spanning tree (MST). If MSTP is implemented a spanning tree can be defined for individual VLANs or for groups of VLANs. Furthermore, the administrator can define alternate paths within a spanning tree. VLANs must be assigned to a so-called multiple spanning tree instance (MSTI). Switches are first assigned to an MST region, then VLANs are mapped against or assigned to this MST. A Common Spanning Tree (CST) is an MST to which several VLANs are mapped, this group of VLANs is called MSL Instance (MSTI). CSTs are backward compatible with the STP and RSTP standard. A MST that has only one VLAN assigned to it is a Internal Spanning Tree (IST).[24]

text: Unlike some proprietary per-VLAN spanning tree implementations,[29] MSTP includes all of its spanning tree information in a single BPDU format. Not only does this reduce the number of BPDUs required on a LAN to communicate spanning tree information for each VLAN, but it also ensures backward compatibility with RSTP (and in effect, classic STP too). MSTP does this by encoding additional region information after the standard RSTP BPDU as well as a number of MSTI messages (from 0 to 64 instances, although in practice many bridges support fewer). Each of these MSTI configuration messages conveys the spanning tree information for each instance. Each instance can be assigned a number of configured VLANs and frames (packets) assigned to these VLANs operate in this spanning tree instance whenever they are inside the MST region. In order to avoid conveying their entire VLAN to spanning tree mapping in each BPDU, bridges encode an MD5 digest of their VLAN to instance table in the MSTP BPDU. This digest is then used by other MSTP bridges, along with other administratively configured values, to determine if the neighboring bridge is in the same MST region as itself.

text: MSTP is fully compatible with RSTP bridges, in that an MSTP BPDU can be interpreted by an RSTP bridge as an RSTP BPDU. This not only allows compatibility with RSTP bridges without configuration changes, but also causes any RSTP bridges outside of an MSTP region to see the region as a single RSTP bridge, regardless of the number of MSTP bridges inside the region itself. In order to further facilitate this view of an MST region as a single RSTP bridge, the MSTP protocol uses a variable known as remaining hops as a time to live counter instead of the message age timer used by RSTP. The message age time is only incremented once when spanning tree information enters an MST region, and therefore RSTP bridges will see a region as only one "hop" in the spanning tree. Ports at the edge of an MST region connected to either an RSTP or STP bridge or an endpoint are known as boundary ports. As in RSTP, these ports can be configured as edge ports to facilitate rapid changes to the forwarding state when connected to endpoints.

text: Shortest path bridging (SPB)[edit]

text:
The IEEE approved the IEEE 802.1aq standard May 2012,[30] also known and documented in most books as Shortest Path Bridging (SPB).  SPB allows redundant links between switches to be active through multiple equal cost paths, and provides much larger layer 2 topologies, faster convergence, and improves the use of the mesh topologies through increased bandwidth between all devices by allowing traffic to load share across all paths on a mesh network.[31][32]
SPB consolidates multiple existing functionalities, including Spanning Tree Protocol (STP), Multiple Spanning Tree Protocol (MSTP), Rapid Spanning Tree Protocol (RSTP), Link aggregation, and Multiple MAC Registration Protocol (MMRP) into a one link state protocol.[33] SPB is designed to virtually eliminate human error during configuration and preserves the plug-and-play nature that established Ethernet as the de facto protocol at Layer 2.[33]

text: System ID Extension[edit]

text: The bridge ID, or BID, is a field inside a BPDU packet. It is eight bytes in length. The first two bytes are the bridge priority, an unsigned integer of 0-65,535. The last six bytes are a MAC address supplied by the bridge. Prior to IEEE 802.1D-2004, the first two bytes gave a 16 bit bridge priority. Since IEEE 802.1D-2004, the first four bits are a configurable priority, and the last twelve bits carry the bridge system ID extension.  In the case of MST, the bridge system ID extension carries the MSTP instance number.  Some vendors set the bridge system ID extension to carry a VLAN ID allowing a different spanning tree per VLAN, such as Cisco's PVST.

text: Disadvantages and current practice[edit]

text: Spanning tree is an older protocol with a longer default hold-down time that governs convergence of the protocol state. Improper use or implementation can contribute to network disruptions. The idea of blocking links is something that customers these days do not accept as a proper high availability solution.  Despite being designed primarily as a guard protocol to manage network topology loops, Spanning Tree Protocol was often misused as a high-availability method.[citation needed] In modern network design it is usually the lack of understanding network media and device operation that result in topology loops whether physical or logical. Modern networks can make use of all connected links by use of protocols that inhibit, control or suppress the natural behavior of logical or physical topology loops.

text: Switch virtualization techniques like HPE IRF, Aruba VSF and Cisco VSS combine multiple switches into a single logical entity. A Multi chassis link aggregation works like a normal LACP trunk, only distributed through multiple switches. Conversely partitioning technologies compartmentalize a single physical chassis into multiple logical entities.

text: On the edge of the network, loop-detection is configured to prevent accidental loops by users.