> [...] > > 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 [EMAIL PROTECTED] 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