RE: BGP keepalive/holdtime at GigE exchange
Hmm, many folks didn't seem to understand the context here. fast-external-fallover doesn't apply if a peer BR across a GigE exchange dies...you've still got link on your Gig port, so there is no link level indication of failure. tweaking tcp timers is not the right approach...BGP explicitly has a keepalive for this exact purpose, when peering dies but your interface stays up. the best non-radical suggestion so far is to simply tweak your keepalive to 10 and holdtime to 30 seconds, to bring this in line with the granularity of direct-connected peer interface or IGP metrics. Do people do this? Do people have problems doing this? Do any folks do less than this on their eBGP peers, and at what tradeoff expense. This is the old issue of finding the right operationally sane timeouts, not too high, not too low. The defaults clearly seem too high, yet I haven't seen many cases where folks set these down :-) Cheers, -Lane
-----Original Message----- From: Lane Patterson [mailto:lpatterson@equinix.com] Sent: Thursday, January 11, 2001 10:08 PM To: 'nanog@merit.edu' Subject: FW: BGP keepalive/holdtime at GigE exchange
I am looking for operational BCP feedback on common practice for tweaking down BGP holdtime/keepalive across GigE exchange points, since a peer could go down on the other side of the GigE switch without a corresponding adjacency change seen on your BR. The thought is to make down peers known as fast thru a GigE exchange as they would be over a POS private peer interface.
The current defaults are pretty gross, and much worse than the ISIS hello and interface keepalive defaults of 10 seconds.
IOS12.x: neighbor [ip-address | peer-group-name] timers keepalive holdtime holdtime: default 180 seconds keepalive: default 60 seconds
http://cco.cisco.com/univercd/cc/td/doc/product/software/ios12 1/121cgcr/ip_r /iprprt2/1rdbgp.htm#xtocid8553
JunOS 4.2: holdtime: default 90 seconds keepalive: default one third of holdtime
https://www.juniper.net/techpubs/software/junos42/swconfig-rou ting42/html/bg p-summary13.html#1015669
Cheers, -Lane
Lane Patterson <lane@equinix.com> Equinix, Inc.
The problem I have seen with setting BGP timeouts that low is when peering with overloaded or slow/old routers. Often they will "pause" their BGP activity while they are actively peering or repeering across their internal or external network. The low times will then cause more timeouts before the fabric has stablized. Deepak Jain AiNET On Fri, 12 Jan 2001, Lane Patterson wrote:
Hmm, many folks didn't seem to understand the context here.
fast-external-fallover doesn't apply if a peer BR across a GigE exchange dies...you've still got link on your Gig port, so there is no link level indication of failure.
tweaking tcp timers is not the right approach...BGP explicitly has a keepalive for this exact purpose, when peering dies but your interface stays up.
the best non-radical suggestion so far is to simply tweak your keepalive to 10 and holdtime to 30 seconds, to bring this in line with the granularity of direct-connected peer interface or IGP metrics.
Do people do this? Do people have problems doing this?
Do any folks do less than this on their eBGP peers, and at what tradeoff expense.
This is the old issue of finding the right operationally sane timeouts, not too high, not too low. The defaults clearly seem too high, yet I haven't seen many cases where folks set these down :-)
Cheers, -Lane
-----Original Message----- From: Lane Patterson [mailto:lpatterson@equinix.com] Sent: Thursday, January 11, 2001 10:08 PM To: 'nanog@merit.edu' Subject: FW: BGP keepalive/holdtime at GigE exchange
I am looking for operational BCP feedback on common practice for tweaking down BGP holdtime/keepalive across GigE exchange points, since a peer could go down on the other side of the GigE switch without a corresponding adjacency change seen on your BR. The thought is to make down peers known as fast thru a GigE exchange as they would be over a POS private peer interface.
The current defaults are pretty gross, and much worse than the ISIS hello and interface keepalive defaults of 10 seconds.
IOS12.x: neighbor [ip-address | peer-group-name] timers keepalive holdtime holdtime: default 180 seconds keepalive: default 60 seconds
http://cco.cisco.com/univercd/cc/td/doc/product/software/ios12 1/121cgcr/ip_r /iprprt2/1rdbgp.htm#xtocid8553
JunOS 4.2: holdtime: default 90 seconds keepalive: default one third of holdtime
https://www.juniper.net/techpubs/software/junos42/swconfig-rou ting42/html/bg p-summary13.html#1015669
Cheers, -Lane
Lane Patterson <lane@equinix.com> Equinix, Inc.
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Deepak Jain -
Lane Patterson