On 7. mars 2010, at 00.07, Claudio Jeker wrote:

> On Sat, Mar 06, 2010 at 06:52:24PM +0100, Rogier Krieger wrote:
>> On Sat, Mar 6, 2010 at 17:26, PP;QQ P(P8P?P8QP8P=
> <chipits...@gmail.com>
>> wrote:
>>> no, I want routes exactly to carp.
>>
>> That sounds odd. Routes are something different than what particular
>> host responds to frames directed to a specific hardware address.
>>
>> If I understand the rest of your description correctly, you want only
>> the master bgpd to have sessions and to somehow distribute its routes
>> to the backup(s), with the backups starting with that 'state' and
>> initiate connections to your BGP peers whenever a master goes down. I
>> doubt that'll work.
>>
>> In your scenario, if your master goes down, there are no longer any
>> BGP sessions up with any of your peers. If I'm not mistaken, that will
>> cause them to withdraw the prefixes you previously advertised from
>> their tables and no longer forward traffic to you.
>>
>
> Right, as soon as the master dies the routes will be withdrawn (there may
> be some overlap since it is possible that carp switches before bgpd
> realizes the loss). At the moment it is not possible to have a real backup
> router running. I have some ideas and partial diffs that will allow backup
> CARP nodes to preload tables. Main problem is that we need graceful
> restart for this but most peers (as in cizzzcoee) are not able to assist
> graceful restart.
>
> Btw. I'm looking for a device that is capable of doing graceful restarts
> (as for example some foundry) to test my diff against. Would be great if I
> could get access to a lab router to play with.
>
>> When your new master is promoted, it will set up a new session with
>> your peers. This is probably not the sort of failover you want to see
>> happening in production.
>>
>
> That's why you have multiple bgpd routers with redundant pathes.
>
> --
> :wq Claudio
>


Not 100% sure what you mean by "...are not able to assist...", but IOS
supports BGP graceful restart as per RFC4724. e.g.:

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html
#wp1049642


/Pete

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