[c-nsp] N7K tcam handling

[Tim Stevenson]

Hi Tim,

Sorry about that, assumed you were talking about ACL TCAM, but you 
are referring to FIB TCAM.

In the scenario you mention, prefixes are installed in the FIB TCAM 
on a first come first served basis. Packets not matching a prefix in 
the FIB TCAM are punted to the CPU, but such traffic is heavily rate 
limited (to protect the inband/CPU), so your routing will be 
considerably hosed. Obviously we syslog such events.

As you probably know, n7k today has a 128K FIB TCAM, inadequate to 
hold full routes anyway. Near-term we will have an XL card that holds 
900K prefixes. In that case, you should not run out of FIB TCAM in 
the case you describe, but as always, you should be sure not to 
"miss" configuring route limits & filters to avoid issues, that's 
clearly best practice.

Hope that helps,
Tim


At 09:31 AM 3/9/2010, Tim Durack clamored:
>Good to know. I was actually thinking more along the lines of: BGP
>peering, missing max-prefix, provider dumps 300k routes on me. What
>does the N7K do? (Unfortunately I know what a 6500 does.)




Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759
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