dCEF VIP and few FIB tables

[lukaszwisniowski]

We have 3 connections to different ISPs on cisco 7507 (3 different AS) and a BGP. There is no transmission between ISPs only between LAN interfaces and internet. I wonder if there is any point to connect ISPs to VIP cards. From theoretical point of view most calculations are made on LAN VIPs while packets travel to the internet because FIB table consist of all BGP routes. At the same time on WAN VIPs (to which ISPs are connected) FIB table could only include local routes which are far smaller than eBGP routes. The problem is that theory says that VIPs obtain identical FIB tables. My thinking leads to the point where all ISPs are connected to interfaces that do not support dCEF and calculations are made by RSP on FIB that consist only local routes. I'm just not sure if it is possible to do it because it would require at least two FIB tables on RSP - one that would have to be copied to VIPs after recalculation (and used for packets that require process switching) of RIB and second one which would include only local routes and would be applied to WAN interfaces.

[wong34539]

if you globally enable distributed CEF, but disable it at interface level, you still have the CEF tables in every VIP and there is no way to avoid it. Simply you are requesting the interfaces not to look into the distributed table to switch the incoming packets, but to look in the RSP CEF table.