[...]
2. Once the limit is reached, excess routes will fail over to software switching. TAC did not specify how routes are designated as excess.
most-specific-prefixes first. it has to be this way due to the way a TCAM search works.
I'm not sure if the Sup2's handle this case differently from the Sup720s we were using, but, in our case, when we reached the ceilign the routes appeared in both the routing and CEF tables but were not populated into the FIB.
Translation: the route was ignored....
how old is the software you were running on your cat6k? reason i ask is that since circa. 12.2(18)SXF9 (i.e. back in 2005), there has been a graceful degradation back to software forwarding for those entries that don't fit into the FIB TCAM: - when the h/w FIB is full (FIB exception) it goes into exception state where it will maintain the longest-prefix-matches by removing shortest- prefix-matches from the FIB TCAM first - it will also insert a default entry to punt lookup exceptions to software - software typically CAN maintain a full FIB, so entries which don't fit into hardware can be software forwarded in the CEF software switching path - when the h/w FIB is full, the following syslog message is generated: MLSCEF-SP-7-FIB_EXCEPTION: FIB TCAM exception, Some entries will be software switched of course, software forwarding is potentially orders-of-magnitude slower than h/w forwarding, so how much extra headroom this gives you once you exceed the capabilities is dependent on the amount of traffic to those prefixes that don't fit into the h/w tables. agree that this isn't "ideal", however Cisco has always been very specific about the h/w FIB & adjacency table sizes on the hardware in question. i know that vendor bashing is a sport in this list, but.... relevant bug-ids if you wanted to look up the details: CSCse90572 syslog message when FIB TCAM exceeds 95% utilization CSCsb18172 wrong packet forwarding at FIB exception if you need further clarification, feel free to contact me off-list, my work email address is ltd@cisco.com. cheers, lincoln. No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.10/977 - Release Date: 28-Aug-07 4:29 PM