[c-nsp] Whats happens when TCAM is full on 7600/RSP720RSP-3CXL?

[Eugene Grosbein]

18.09.2020 15:54, chiel wrote:

> I'm currently using a 7606 (RSP720RSP-3CXL) and taking in full BGP on v4 and v6.
> Obviously it the TCAM is almost full and the box needs to be replaced.

I use same router with two copies of full BGP on v4 and v6.
There is a way to mitigate the problem without replacing the box.

The following configuration places a filter on routes being installed
from BGP RIB to TCAM (FIB) limiting its usage by length of AS-PATH,
so traffic to very distant networks goes via default route.

This way, "show platform hardware capacity" shows:

 Module              FIB TCAM usage:                     Total        Used     %Used
   5                     72 bits (IPv4, MPLS, EoM)      884736      422247     48%
                        144 bits (IP mcast, IPv6)       81920         8412     10%
Works fine for me.

mls cef maximum-routes ip 850
mls cef maximum-routes mpls 1
router bgp NNNN
 address-family ipv4
  table-map BGP2FIB filter
 address-family ipv6
  table-map BGP6FIB filter
!
route-map BGP2FIB permit 10
 match as-path 400
!
route-map BGP2FIB permit 20
 match ip address prefix-list SELECTED-SET
!
route-map BGP6FIB permit 10
 match as-path 500
!
ip as-path access-list 400 deny ^.+_.+_.+_.+
ip as-path access-list 400 deny ^.+_65535$
ip as-path access-list 400 permit ^.*
ip as-path access-list 500 deny ^.+_.+_.+
ip as-path access-list 500 deny ^.+_65535$
ip as-path access-list 500 permit ^.*