[c-nsp] MPLS affecting normal IP cache flows

[David Curran]

Seems like you might need the "mpls netflow egress" command since this is a
backbone interface.


> From: "Oliver Boehmer (oboehmer)" <oboehmer at cisco.com>
> Date: Wed, 6 Aug 2008 08:28:24 +0200
> To: Andy Saykao <andy.saykao at staff.netspace.net.au>,
> <cisco-nsp at puck.nether.net>
> Subject: Re: [c-nsp] MPLS affecting normal IP cache flows
> 
> Andy Saykao <> wrote on Wednesday, August 06, 2008 5:19 AM:
> 
>> Hi All,
>> 
>> I've deployed MPLS across parts of our core network and everything
>> appears to be working fine. I've also got MPLS VPN's going which is
>> the main reason for us rolling out MPLs in the first place.
>> 
>> However, I've run into a problem with netflow on one of the PE routers
>> that affects normal IP flows when mpls is enabled on the interface.
>> The PE router having this problems is a cisco 7206VXR (NPE-G1) running
> IOS
>> Version 12.3(22). Other PE routers are not showing this problem but
>> they are 7301's running a different IOS.
>> 
>> What I'm finding is that when I enable "tag-switching ip" on interface
>> Gi0/2 which forms part of our MPLS core (as seen below), the netflows
>> for normal IP traffic isn't as it should be. Doing a "show ip cache
>> flow" on the PE router only shows a few flows going through for normal
>> IP traffic and we'd expect more IP cache flows to be going through
>> because lots of customers hang off this PE router. When we remove the
>> "tag-switching ip" from the interface, flows are back to normal.
> [..]
>> Any ideas as to why enabling mpls would be affecting normal IP cache
>> flows? I can only suspect that it's some IOS bug with the IOS we're
>> running .
> 
> do you filter any LDP advertisements? If you just enable LDP on the
> interface (or TDP for that matter), "regular" IPv4 traffic will also be
> label-switched as LDP advertises labels for all non-BGP IPv4 prefixes in
> your RIB. Can you do a "show mpls forwarding-table <prefix>" for a
> prefix you would expect to see in the cache? Do you see a incoming label
> (which is != Pop label)?
> 
> oli
> 



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