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I am Val Glinskiy, network engineer specializing in data center networks. TIME magazine selected me as Person of the Year in 2006.

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Wednesday, September 17, 2008

SUP720-3C TCAM exeption

If you are running BGP on Catalyst 6500 or 7600 with SUP 72-3C and receiving full routing table from a peer, sooner rather than later you'll get this message
%CFIB-SP-7-CFIB_EXCEPTION: FIB TCAM exception, Some entries will be software switched
Meaning that your router's performance will be degraded, since some of the traffic processed by CPU as opposed to hardware. The only way to get out of this state is to reboot the router. Here is how to check whether your router is in exception state:

cisco-7600#show mls cef exception status
Current IPv4 FIB exception state = TRUE
Current IPv6 FIB exception state = FALSE
Current MPLS FIB exception state = FALSE

If you are not running IPv6 or MPLS you can postpone inevitable upgrade to 720-3CXL by allocating entire TCAM memory to IPv4 routes
cisco-7600#mls cef maximum-routes ip 239

To see TCAM utilization
cisco-7600##show platform hardware capacity | begin L3 Forwarding Resources
L3 Forwarding Resources
FIB TCAM usage: Total Used %Used
72 bits (IPv4, MPLS, EoM) 196608 184013 94%
144 bits (IP mcast, IPv6) 32768 3 1%

.....skipping the rest