HOWTO:CISCO:7200VXR
In this case, an old C7206VXR was used to test an upgrade from its a basic 2 full BGP routing tables to include uRPF support to inside interfaces.
It is the perfect case to demonstrate that a good understanding/evaluation of your platform is a prerequisite to a stress free upgrade.
The commands to apply are:
- ip cef
- interface fastethernet 5/0
- ip verify unicast source reachable-via rx
With 60MB of free memory left, executing "ip cef" in order to enable "ip verify" on the inside interface resulted in a crash:
Mar 30 20:05:02 EDT: %FIB-3-NOMEM: Malloc Failure, disabling CEF <snip>
CEF should be considered as another full routing table, which in this case is over 70MB of RAM.
All is not lost, an access list can be applied to the customer interface. While the solution is not as maintenance free as "ip verify" a note can be added to the banner to inform your technical personnel of the access list.
