[rbak-nsp] BGP - GracefulRestart & BFD - how does it work ?

[Yuri Shefer]

Hi Marcin,

Please see inline


On Thu, Jun 13, 2013 at 2:48 PM, Marcin Kuczera <marcin at leon.pl> wrote:

>  On 2013-06-13 18:28, Yuri Shefer wrote:
>
> Hi Marcin,
>
>  The BFD is running on the line card. If you enable BFD for your eBGP
> neighbor, the BGP will become a client for BFD, i.e. BGPd process will be
> notified if the BFD session fails.
>
>  The config part is very simple:
>
>  context bfd-bgp
>   router bfd
>   interface to-as123
>    minimum transmit-interval 100
>    minimum receive-interval 100
>    detection-multiplier 3
>
>  router bgp 123
>   neighbor 1.1.1.2 external
>    bfd
>
>
>
> Ok, config is quite clear. Dependencies between processes also.
> However:
>
> - if BFD runs on linecard, what happens if linecard crashes ? Is it able
> to inform bgpd then ?
>

This is different kind of events. The line card failure event have
different handling procedure, but result is the same - all processes will
receive appropriate notification. However, in case of iBGP or multihop eBGP
session you may want to have "fast-reset" option configured.



> I suppose that there is some BFD parent process on XCRP that controls BFD
> on linecards, but - is it ?
>

RIB is responsible for BFD provisioning from control plane side.


>
> - I assume that BFD informing BGPd causes all bgp session timers clear
> down instantly. Right ?
>
>
Yes, that is the reason why you would want to use BFD for eBGP sessions.

-- 
Best regards,
Yuri
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/redback-nsp/attachments/20130614/b591088d/attachment.html>