[c-nsp] CEF wrong next hop

[rwcrowe at comcast.net]

In the meantine while you identify if it is a bug or not, you can turn on the cef consistency check to try to correct the information.
http://www.cisco.com/en/US/partner/tech/tk827/tk831/technologies_tech_note09186a00800946f7.shtml
--
Rob Crowe 
rwcrowe at comcast.net


-------------- Original message -------------- 

> 
> In 12.3(7)T1 we've noticed a problem running CEF whereby 
> certain routes show the incorrect next hop (i.e. different from the routing 
> table) and result in routing loops. According to this document 
> (http://www.cisco.com/en/US/tech/tk827/tk831/technologies_tech_note09186a008 
> 00cdf2e.shtml) this could occur if the routes were discovered via proxy arp 
> on the interface. This is not the situation in our case, though the 
> _results_ are quite similar. 
> 
> This bug: 
> http://www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCee74177&cco_ 
> product=IOS&fset=CEF/DCEF/FIB&swver=12.3&keyw=&target=7&train=T1 
> 
> is actually quite similar compared to what we are seeing, however unlike 
> that bug, when we kill CEF on our router the routing then returns to normal 
> (next hop learned via BGP), and all is well in the universe. I am wondering 
> if anyone else has seen the same or similar bug on the T train, as we also 
> have the same issue with another route on a router running version 
> 12.2(17a). 
> 
> I'm assuming for the moment that it is a bug, simply because the behaviour 
> seems strange, and the bug is listed as not reproducible, and it is so very 
> close to our situation. As well, I do not think it is normal for CEF to 
> have differing next hops from the entries in the routing table. 
> 
> Any advice would be appreciated, even if it is just to confirm that this is 
> a bug. 
> 
> Thanks, 
> 
> Tim Devries 
> 
> 
> 
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