[j-nsp] MX NSR issue

[Felix Schueren]

Chris,


> 
> #1 - I have two eBGP neighbors using BFD. One of the neighbors tripped, now
> BFD won't re-establish. BGP is up however.
> #2 - I'm using IRB interfaces on the MX platform. After the failover,
> traffic will not forward.. You can communicate RE to host, but HOST to HOST
> on the same box or external<>HOST connectivity is broken.

I sometimes experience issues on RE failover on M- and MX-Boxes. Here's
a snippet of a case I opened about a year ago:


+++snip+++
the effect was that the router was left in a half-working state - IS-IS
was up, most IPv4 BGP peerings were up (but not all of them), none of
the IPv6 BGP peerings were up. Pings to the loopback address were not
possible, we could not ping some directly attached hosts even though ARP
was working fine. There were no error messages or any indication of
anything being wrong. When testing locally via ping from the router CLI,
we got "sendto: operation not permitted" messages. The NTP daemon was
logging "sendto(x.x.x.x): Operation not permitted" (and did not work),
ping to y.y.y.y (a directly attached host in the same subnet as x.x.x.x,
living in z.z.z.z/27) returned the same "operation not permitted"
messages, but ARP was working fine.

one of the not-working BGP sessions logged this:
task_connect: task BGP_remoteAS.a.b.c.d+179 addr a.b.c.d+179: Operation
not permitted

"restart routing" (at 05:24 CEST) did not help.
+++snip+++

the remedy for this was (and has been everytime I ran into this, about
once a year since 2004): remove lo0-filters, commit, activate
lo0-filters, commit. The instant the commit with deactivated lo0-filters
is finished, everything works properly, and continues to work even with
the lo0 filters back in place.

A race condition of some sort, maybe?

kind regards,

Felix

-- 
Felix Schüren
Head of Network

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