From: Rich Collins (nilsi2002@gmail.com)
Date: Thu Nov 20 2008 - 14:20:56 ARST
Hello,
I just tried a very similar scenario to yours (Uniform mode) with dynamips.
If I turned on "debug mpls packet"on P1 (where the match and rewrite of the
EXP occurs) then the policy maps/service policies wouldn't work. It
confused me because I had seen some increment in the counters but that was
from the time before I had activated the debug. So it worked properly after
turning off this debug and observing further along in the P core such as on
your R4 (enabling debug mpls packet here).
Is there some caveat when using "debug mpls packet"?
-Rich
On Mon, Nov 17, 2008 at 11:40 AM, Con Spathas <ccie19226@googlemail.com>wrote:
> Gday,
>
> I think I'm missing something quite fundamental here but I can't seem to
> find the reason why...
>
> I have the following setup:
>
> R1 (CE) - R2 (PE) - R3 (P) - R4 (P) - R5 (PE) - R6 (CE)
>
> R2 is matching ICMP inbound from R1 and marking it MPLS EXP 4
> R3 is matching MPLS EXP 4 from R2 and remarking it to MPLS EXP1
>
> I see that is happening when I debug on R4 (the COS=4 on the XMIT is the
> VPN
> label) which is what I expect as R5 is currently sending implicit null to
> R4.
> If I configure R5 to advertise explicit null in LDP, the debug output
> changes correctly and the xmit CoS = 1. Anyhow that's not my issue - just
> background info.
>
> R4
> *Mar 1 02:40:51.859: MPLS: Et0/0.34: recvd: CoS=1, TTL=253, Label(s)=19/21
> *Mar 1 02:40:51.863: MPLS: Et0/0.45: xmit: CoS=4, TTL=252, Label(s)=21
>
> The bit that is eluding my understanding is the output on R3.
>
> R3
> *Mar 1 00:10:59.075: MPLS: Et0/0.23: recvd: CoS=4, TTL=254, Label(s)=17/21
> *Mar 1 00:10:59.079: MPLS: Et0/0.34: xmit: CoS=4, TTL=253, Label(s)=19/21
>
> I can't work out why the xmit is showing the CoS=4 - even though R4 does
> receive it as CoS=1 ? I expected on R3 to see CoS=1 on the XMIT.
>
> This is the policy map in have inbound on R3's connection to R2.
>
> class-map match-all EXP4
> match mpls experimental topmost 4
> !
> policy-map IN
> class EXP4
> set mpls experimental topmost 1
>
> The policy-map output is incrementing counters correctly. So whilst the
> re-marking is working - I don't quite understand why the debug on R3 isn't
> consistent with what I subsequently see on R4.
>
> Any insight would be great. Thanks.
>
> Con.
>
>
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