[c-nsp] Hierarchical FIB on Cisco 7600

Adam Vitkovsky Adam.Vitkovsky at gamma.co.uk
Sat Apr 23 15:38:27 EDT 2016

> James Bensley
> Sent: Thursday, April 21, 2016 5:55 PM
> Hi All,
> Reviving this old thread, is anyone running a hierarchical FIB on a 7600, how is
> it working for you? Has it halved your PPS rate for
> VPNv4/VPNv6 traffic due to recirculation?
Sorry can't comment on this

> PIC Edge is “working” in that backup prefixes are installed into FIB however I
> haven’t been able to do any failover timing tests. I would still expect this to
> be fairly quick since the backup prefix is computed and programmed into FIB.
> In a PIC edge scenario only a small number (usually) of prefixes are being
> updated due to a CE-PE failure, comparatively speaking to a P/PE node failure
> which may require a set of full-table prefixes that need next-hop updates.
Quick and easy test would be to run a ping test and you shouldn't lose a single packet.

> In the case that a PE connected to a transit provider goes bang the 7600s are
> still slow to update. I don’t even have to measure this I can see it when
> performing maintenance work on transit links (CPU shoots to 100% and SSH
> slows down a bit etc whilst BGP churns).
To solve this you can use bgp pic-core then the speed of convergence would be reduced to how fast the IGP can propagate the BGP NH failure to ingress PE (that you can tune as well).


        Adam Vitkovsky
        IP Engineer

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E:      Adam.Vitkovsky at gamma.co.uk
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