[nsp] Cat6500/MSFC2 CEF issue

[Joel Lafleur]

Additionally, I've heard of the same problem occurring, requiring the same
resolution, on the 12000 GSR devices.  YMMV.

Joel

> -----Original Message-----
> From: Todd, Douglas M. [mailto:DTODD@PARTNERS.ORG]
> Sent: August 26, 2002 9:57 AM
> To: 'Scott.Keoseyan@BroadWing.com'; cisco-nsp@puck.nether.net
> Subject: RE: [nsp] Cat6500/MSFC2 CEF issue
> 
> 
> 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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