p.mayers at imperial
Apr 13, 2012, 9:05 AM
Post #1 of 2
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NX-OS 6.0(1) BGP graceful restart on SUP failover
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Does anyone have this working?
I am testing an N7k with dual SUP, and when I perform a failover, BGP
graceful restart is not working as expected. I have a TAC case open, but
was wondering if anyone else had run into it.
The symptoms are:
1. The initial BGP session has the "graceful restart" capability
negotiated, and the expected AFI/SAFI marked for GR.
2. When I perform "system switchover", the box continues to forward
traffic, and the neighbour continues to send it traffic.
3. Once the 2nd SUP becomes active, it establishes a new BGP peering.
In the OPEN message, the "flags" of the GR capability has the R-bit set
(indicating restart has occurred) but the F-bit for each AFI/SAFI is set
to 0 - the neighbour thus assumes forwarding was not preserved, and
discards the stale routes.
So, I have the odd situation that, after a switchover, forwarding works
for about 20 seconds, then stops as the SUP effectively commits "BGP
suicide" by telling the peer that forwarding didn't work!
This is on M-series linecards, in an MPLS/L3VPN config if that matters -
though I am fairly sure it's a problem at the BGP level, since packet
forwarding did continue, stopping immediately upon the new BGP session
startup i.e. step #3 above.
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