[c-nsp] BGP Next hop tracking / 'hold down' route...

[Andrew Brant]

The BGP Selective Address Tracking feature introduced the use of a route map with BGP fast session deactivation. The route-map keyword and map-name argument are used with the neighbor fall-over BGP neighbor session command to determine if a peering session with a BGP neighbor should be reset when a route to the BGP peer changes. The route map is evaluated against the new route, and if a deny statement is returned, the peer session is reset. The route map is not used for session establishment. 

Sent from my iPhone

On Jun 25, 2013, at 9:12 AM, Andrew Brant <andrew.brant at me.com> wrote:

> Fall-over combined with next hop tracking creates another distinct feature called selective address tracking:
> 
> The following commands are new or modified for this feature:
> •bgp nexthop
> •neighbor fall-over
> http://www.cisco.com/en/US/docs/ios/12_4t/12_4t4/ht_bgpsn.html
>>>    neighbor 192.168.25.7 fall-over route-map RTM-BGP-
>>> FALLOVER
> 
> Cheers,
> Andrew
> 
> CCIE 14715
> 
> Sent from my iPhone
> 
> On Jun 25, 2013, at 1:16 AM, Saku Ytti <saku at ytti.fi> wrote:
> 
>> On (2013-06-24 23:19 -0500), Andrew Brant wrote:
>> 
>>>    neighbor 192.168.25.7 fall-over route-map RTM-BGP-
>>> FALLOVER
>> Fall-over and next-hop tracking are two distinct features.
>> With next-hop tracking, you simply invalidate the next-hops there by
>> invalidating the routes and choosing next-best option.
>> With fall-over you tear down whole session, this is usually undesirably
>> large hammer, consider your IGP flap is very short, if you tore down the
>> iBGP it might take minutes to recover.
>> 
>> But granted, if current version does not support selective next-hop
>> resolution it seems like significantly better than nothing.
>> 
>> 
>> -- 
>>  ++ytti
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