BGP Hold Timer 1

[StarTAC]

hi all...

i am setting up a backup link with BGP, and would like the failover to happen almost transparently, so users don't notice a loss in service..

because of this, i'd like to modify the BGP holdtime timer, from the default of 180 seconds, to something lower, say 30 seconds... however, this would mean lowering the keepalive timer as well, as it defaults to 60 seconds, which would be higher than the holdtime timer, rendering the neighbor down..

so, what if i modify the keepalive timer to 10 seconds, and change the holdtime timer to say 30 seconds [3x the keepalive timer], my main question is, does the BGP peer on the other side need to have the same timer settings for the BGP session with me..?.. will BGP negotiate them automatically, or they will need to be told to make the changes to their default timers too..

all help appreciated..

 

[tschouten]

BGP uses certain timers to control periodic activities such as the sending of keepalive messages, and the interval after not receiving a keepalive message after which the Cisco IOS software declares a peer dead. By default, the keepalive timer is 60 seconds, and the holdtime timer is 180 seconds. You can adjust these timers. When a connection is started, BGP will negotiate the hold time with the neighbor. The smaller of the two hold times will be chosen. The keepalive timer is then set based on the negotiated hold time and the configured keepalive time.

Command to use:

timers bgp keepalive holdtime

You can also set neighbor timers:

neighbor [ip-address | peer group-name] timers keepalive holdtime

Purpose for the above command: Sets the keepalive and holdtime timers (in seconds) for the specified peer or peer group


Hope that answers your question.

 

[StarTAC]

cheers mate.. that's all i needed to know.. that the timers will be negotiated on peer-up, and the smaller of both neighbors chosen..

many thanks..

 

[tschouten]

Glad I could help