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

[Marcin Kuczera]

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

- I assume that BFD informing BGPd causes all bgp session timers clear 
down instantly. Right ?

Regards,
Marcin


>
>
> To verify that the BGPd is correctly registered for receiving BFD 
> events, you can check "show bfd session details" and under the 
> "Client" you would see bgp.
>
> On Thu, Jun 13, 2013 at 5:49 AM, Marcin Kuczera <marcin at leon.pl 
> <mailto:marcin at leon.pl>> wrote:
>
>     hello,
>
>     I have a customer who has a customer that is very sensitive to BGP
>     failovers.
>     I mean - holdtime is a problem if there is a real fault between
>     routers (not just bgpd restart).
>
>     There is quite long timeout - restart 120s + 90s of holdtime..
>
>     Ok, we don't have problems everyday - but recently before upgrade
>     to 12.1.1.2 we did for a week.
>     So I need to find some soft solution for future cases.
>
>     Now, I'am wondering what will happen if we start using BFD between
>     our and our customer routers.
>     Is the BDF for BGP a separate process from bgpd ?
>
>     I mean - I would like to keep graceful restart for bgpd crash
>     cases, and BFD for linecard crashes case.
>     Does anyone has an experience using these features together and
>     could share its opinion ?
>
>     (and drop a example of BFD config for a BGP peer ;)
>
> -- 
> Best regards,
> Yuri

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