[nsp] Cat6500/MSFC2 CEF issue

[Todd, Douglas M.]

Scott:

We had this problem with ip route to null0.  This seems like a bug since you
remove it the CEF table keeps the entry. Doing a sh ip route stated the route in
the table correctly, but traffic would not forward to the network.

Resolution:
 We added the route again with the entry to a different address and removed it
and the null0 entry was removed.  I think this is a bug w/cef.

ie:

ip route 10.0.0.0 255.0.0.0 null0
ip route 10.0.0.0 255.0.0.0 10.1.1.1
no ip route 10.0.0.0 255.0.0.0 10.1.1.1

==DMT>

> -----Original Message-----
> From: Scott.Keoseyan@BroadWing.com 
> [mailto:Scott.Keoseyan@BroadWing.com]
> Sent: Monday, August 26, 2002 6:00 AM
> To: cisco-nsp@puck.nether.net
> Subject: [nsp] Cat6500/MSFC2 CEF issue
> 
> 
> Hello!
> 
> I had to put a static host route pointing to null0 to eliminate some
> troublesome traffic for a particular host on an MSFC2 the 
> other day.  When I
> cleared the static route, the only route left was for the 
> entire /24 (learnt
> via IGP), however the CEF entry for the host would not clear, 
> and continued
> to point the adjacency to null0.
> 
> I ended up creating another static host route for the host 
> and pointing down
> the correct path in the network.  Then I cleared this route, 
> and the CEF
> adjacency reverted to the correct entry, showing the 
> adjacency for the /24
> learnt via my IGP.
> 
> My question is, is there a particular concern with routes 
> pointed to null0
> when it comes to CEF?  Shouldn't my removal of the static host route
> automatically force CEF to revert to the next best learnt 
> path since the
> only thing left in the route-table was the route for the 
> entire /24?  Why
> should the next-hop make a difference, whether I pointed the 
> static route at
> a null0 interface or a serial interface when it comes to CEF? 
>  Why didn't
> the removal of the route clear the CEF entry the first time 
> but work the
> second time?
> 
> Most comments are appreciated...
> 
> thanks,
> 
> Scott Keoseyan
> 
> 
> 
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