[c-nsp] Clearing CEF entry (routing loop)

[Oliver Boehmer (oboehmer)]

Ihsan Junaidi Ibrahim <> wrote on Thursday, October 27, 2005 6:40 AM:

> A routing loop has occurred in my network. I have 2 routers, R1 and
> R2 in which R2 is connected directly to R1 and R1 to our core
> network. Checking my routing table in both routers, the prefix is
> being forwarded to transit provider T1 however the CEF entry is
> pointing to another router, R3 connected to another transit provider
> T2. My CEF entry at R1 is pointing to R2 as the next hop however at
> R2, the next hop entry is pointing to R1 because R3 is accessible
> only via R1. So the packets are stuck in a perpetual loop.
> 
> I did try variations of clear ip cef commands such as
> "clear ip cef xxx.xxx.xxx.xxx/18 prefix-statistics"
> "clear ip cef xxx.xxx.xxx.xxx 255.255.192.0 prefix-statistics"
> 
> but still no avail. The CEF entry for that particular route still
> points to R3.

"clear ip route xxx.xxx.xxx.xxx 255.255.192.0" should fix this as it
causes a new CEF entry to be created. 
Another chance could be "clear ip cef epoch" (depends on Release you are
using) which rebuilds the CEF tables.

	oli