[j-nsp] MX960 NSR Problem

[Walaa Abdel razzak]

OK, That's why I see BGP session reset on the new Backup RE but not on
the new master because of resync process and we can say this behaviour
is normal. But why the BFD, ISIS sessions was reset on the new master
and affected neighbours state?

Best Regards,
Walaa Abdel Razzak

-----Original Message-----
From: Richard A Steenbergen [mailto:ras at e-gerbil.net] 
Sent: Monday, July 13, 2009 12:55 AM
To: Walaa Abdel razzak
Cc: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] MX960 NSR Problem

On Sun, Jul 12, 2009 at 08:36:12PM +0300, Walaa Abdel razzak wrote:
> Experts
> 
> I have MX960 router with JUNOS 9.4R2 having GRES and NSR enabled. When
I
> switch from the master to backup RE, Traffic is not interrupted but
the
> protocols appears to reset on the old master but the strange thing is
> that it appears not reset on the new master, do you have reason for
> this? The BGP on the neighbor routers didn't flap, but ISIS, BFD
session
> flapped on the neighbors.

That is how NSR is supposed to work. When running NSR, the backup RE is 
pre-synchronized to the state of the active RE, so when you do a 
switchover the BGP session appears to be uninterrupted. At some point 
after the switchover is completed, the new backup RE should sync up in 
the same way, but it won't be instant.

BTW if I were you I'm not sure that I would be running NSR in production
on 9.4R2. I've seen a lot of bugs related to it (and even related to
GRES, ever since around 9.1+ it has been very sketchy for me) which can
cause disruptions or even blackholing within packet forwarding when
"something" happens on the backup RE. LDP sessions resetting whenever 
the backup RE was rebooted was extremely annoying. :)

-- 
Richard A Steenbergen <ras at e-gerbil.net>
http://www.e-gerbil.net/ras
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