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FTOS Configuration Guide for the C-Series - Force10 Networks

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Change BGP timers<br />

Use ei<strong>the</strong>r or both of <strong>the</strong> following commands in <strong>the</strong> CONFIGURATION ROUTER BGP mode to<br />

configure BGP timers.<br />

Command Syntax Command Mode Purpose<br />

neighbors {ip-address |<br />

peer-group-name} timers keepalive<br />

holdtime<br />

CONFIG-ROUTER-<br />

BGP<br />

timers bgp keepalive holdtime CONFIG-ROUTER-<br />

BGP<br />

Use <strong>the</strong> show config command in CONFIGURATION ROUTER BGP mode or <strong>the</strong> show<br />

running-config bgp command in EXEC Privilege mode to view non-default values.<br />

Timer values configured with <strong>the</strong> neighbor timers command override <strong>the</strong> timer values configured with<br />

<strong>the</strong> timers bgp command.<br />

When two neighbors, configured with different keepalive and holdtime values, negotiate <strong>for</strong> new values,<br />

<strong>the</strong> resulting values will be as follows:<br />

• <strong>the</strong> lower of <strong>the</strong> holdtime values is <strong>the</strong> new holdtime value, and<br />

• whichever is <strong>the</strong> lower value; one-third of <strong>the</strong> new holdtime value, or <strong>the</strong> configured keepalive value is<br />

<strong>the</strong> new keepalive value.<br />

BGP neighbor soft-reconfiguration<br />

Configure timer values <strong>for</strong> a BGP neighbor or<br />

peer group.<br />

• keepalive range: 1 to 65535. Time interval, in<br />

seconds, between keepalive messages sent<br />

to <strong>the</strong> neighbor routers. (Default: 60 seconds)<br />

• holdtime range: 3 to 65536. Time interval, in<br />

seconds, between <strong>the</strong> last keepalive message<br />

and declaring <strong>the</strong> router dead. (Default: 180<br />

seconds)<br />

Configure timer values <strong>for</strong> all neighbors.<br />

• keepalive range: 1 to 65535. Time interval, in<br />

seconds, between keepalive messages sent<br />

to <strong>the</strong> neighbor routers. (Default: 60 seconds)<br />

• holdtime range: 3 to 65536. Time interval, in<br />

seconds, between <strong>the</strong> last keepalive message<br />

and declaring <strong>the</strong> router dead. (Default: 180<br />

seconds)<br />

Changing routing policies typically requires a reset of BGP sessions (<strong>the</strong> TCP connection) <strong>for</strong> <strong>the</strong> policies<br />

to take effect. Such resets cause undue interruption to traffic due to hard reset of <strong>the</strong> BGP cache and <strong>the</strong><br />

time it takes to re-establish <strong>the</strong> session. BGP soft reconfig allows <strong>for</strong> policies to be applied to a session<br />

without clearing <strong>the</strong> BGP Session. Soft-reconfig can be done on a per-neighbor basis and can ei<strong>the</strong>r be<br />

inbound or outbound.<br />

BGP Soft Reconfiguration clears <strong>the</strong> policies without resetting <strong>the</strong> TCP connection.<br />

512 Border Gateway Protocol (BGP)

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