GSR and bgp maximum-paths

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1

Long time listener, first time caller.

I would like to enable multipath bgp on a GSR running 12.0(10)S that has two
bgp neighbors in the same AS connected via OC-3 pos in order to load balance
outbound traffic across the two pos connections.

I've checked out the cisco bug search and haven't found any for this feature
on this release of IOS.

Is anyone else have any problems with "maximum-paths" on a GSR and if yes,
what release of IOS? Any other issues I should be aware of?

Thanks,

James

2

Is anyone else have any problems with "maximum-paths" on a GSR and if yes,
what release of IOS? Any other issues I should be aware of?

It may not affect you (given you are running 12.0(10)S), but having
maximum-paths set to something other than 1 can cause problems on
Engine 2 linecards. The result is that the CEF IPC Background
process eats all available linecard CPU. Packet forwarding is not
directly affected, but it can mean that the CEF tables take a long
time to converge after a routing flap.

As far as I am aware the bug was introduced around 12.0(13.6)S, and
has not been fixed in any releases so far.

However, this is starting to stray into cisco-nsp territory. :slight_smile:

Rob

3

Rob Evans <rhe@noc.ten-155.net> writes:

> Is anyone else have any problems with "maximum-paths" on a GSR and if yes,
> what release of IOS? Any other issues I should be aware of?

It may not affect you (given you are running 12.0(10)S), but having
maximum-paths set to something other than 1 can cause problems on
Engine 2 linecards. The result is that the CEF IPC Background
process eats all available linecard CPU. Packet forwarding is not
directly affected, but it can mean that the CEF tables take a long
time to converge after a routing flap.

As far as I am aware the bug was introduced around 12.0(13.6)S, and
has not been fixed in any releases so far.

  BugTrack ID?

-tex

4

> As far as I am aware the bug was introduced around 12.0(13.6)S, and
> has not been fixed in any releases so far.

  BugTrack ID?

Sure, but things have changed since the above was written. :slight_smile:

It is fixed in 12.0(15)S2 -- the BugID is CSCdt56314.

Cheers,
Rob