[c-nsp] Hierarchical FIB on Cisco 7600

James Bensley jwbensley at gmail.com
Thu Apr 21 12:55:01 EDT 2016

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?

The Cisco documentation is fairly light and ambiguous. L2 and L3 VPNs
are a major bread-and-butter at $dayjob so halving the PPS rate for
MPLS VPN traffic through these boxes would be quite serious :)

Also what about memory usage, at 2KBs per prefix carrying the full
table plus customer routes on our 7600s (RSP-720-3CXLs) it looks like
I couldn’t even turn it on if I wanted to?

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.

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).


More information about the cisco-nsp mailing list