[f-nsp] Bigiron RX4 - IPV6 causing out of nexthop entries

[Pieter Taks]

Hi everyone,

I seem to be having problems with IPV6 on a Bigiron RX4 causing out of
nexthop entries.

Situation:
* We have a transit provider delivering 2x ipv6 BGP sessions with each
~6800 routes.
* Router is also doing 2x ipv4 BGP sessions with the same provider (no
problems here).

Problem:
Once in a while (every other week or so) for some reason the router gives
the following in the syslog:
Aug 13 11:30:07:I:INFO: Out of nexthop entries for path count 7 on slot 3.
Aug 13 11:30:07:I:INFO: Out of nexthop entries for path count 7 on slot 1.
Aug 13 11:30:07:I:INFO: Out of nexthop entries for path count 7 on slot 2.
Aug 13 11:30:07:I:INFO: Out of nexthop entries for path count 7 on slot 4.



When it does the following output is visible. See that it changes, I ran
it twice pretty much no more than 5 seconds apart.

#sh ip nexthop
Module S1:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    0      256

Module S2:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    0      256

Module S3:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    0      256

Module S4:

Paths  Total  Free  In-use
  1    2816   2804   12
  2    512    512    0
  4    512    512    0
  8    256    0      256

#sh ip nexthop 
Module S1:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    8      248

Module S2:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    8      248

Module S3:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    8      248

Module S4:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    8      248



However when I shutdown one ipv6 BGP session with the transit provider,
the following output is given.

#sh ip nexthop

Module S1:

Paths  Total  Free  In-use
  1    2816   2804   12
  2    512    512    0
  4    512    512    0
  8    256    232    24

Module S2:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    232    24

Module S3:

Paths  Total  Free  In-use
  1    2816   2805   11
  2    512    512    0
  4    512    512    0
  8    256    232    24

Module S4:

Paths  Total  Free  In-use
  1    2816   2804   12
  2    512    512    0
  4    512    512    0
  8    256    232    24



The VE having the IPV6 address:
 ipv6 address x:x:x:x::1fa/126
 ipv6 enable
 ipv6 nd suppress-ra


BGP config:
 neighbor ipv6-x peer-group
 neighbor ipv6-x remote-as y
 neighbor ipv6-x next-hop-self
 neighbor ipv6-x remove-private-as
 neighbor ipv6-x soft-reconfiguration inbound

 neighbor x:x:x:x::1f9 peer-group ipv6-x


 address-family ipv6 unicast
 maximum-paths 2 
 multipath ebgp
 redistribute connected
 neighbor ipv6-x activate
 neighbor ipv6-x route-map in ipv6-x-in
 neighbor ipv6-x route-map out ipv6-x-out
 neighbor x:x:x:x::1f9 activate


route-map ipv6-x-in permit  10
 set local-preference 100
 set metric none



Also when we re-enable the ipv6 BGP session again it still gives the same
output as above. No problems visible then anymore and it might out of blue
appear later on again. This might also mean it has not a direct relation
with the ipv6 BGP session(s). However it does 'resolve' the issue for the
time being.

We have ran version 2.7.3a, 2.8.0 and now version  2.7.2k. All 3 versions
seem to have this issue.

I hope someone has any idea what might be the cause of this, either way
thank you all for reading.

-- 
Best regards,
 
Pieter Taks