[c-nsp] MPLS, MTU and POS (STM-1) "problems"

[Primoz Jeroncic]

On Tue, 13 Sep 2005, Mikael Abrahamsson wrote:

> On Tue, 13 Sep 2005, Primoz Jeroncic wrote:
>
> Do something like "mpls mtu 1546" on all interfaces you're running MPLS
> on.

Thanks Mikael for your suggestion. I tried this in my test environment and it's
working fine after I put "mpls mtu 1546" on all MPLS enabled ports. Only
"problem" I have is that on 7206VXR, I have only chance to put "mpls mtu 1524"
and not 1546 (on all other routers (c1841, c2811, c3640, c7401, gsr) I have
option of 1546).
Now while this is working on my fastethernet on test 7206vxr in my lab it
doesn't look like it would be working in real life.
When I finished pretty much every possible scenario on my test network I tried
to put this in real life (instead of fastethernet I have Gigabitethernet on
7206vxr), I still have same problem. From all other routers in network it's
working now, but everything what goes through 7206vxr still can't access GSR (P4)
on other side of STM-1, even though mpls mtu is set to 1546 (and 1524 on 7206vxr)
all over the path (on mpls enabled ports of course)
Btw if it matters... 7206vxr is running Service provider IOS 12.2.25 S25. But
the one in lab was running same version of IOS so I guess it's not and IOS
issue.
Thanks again for any other ideas which could help me solve this.

Have nice rest of day... or night :)
Primoz Jeroncic
Support - IP Connectivity & Routing
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> > Hi everyone
> >
> > I know I'm probably missing something really basic here, but at 10pm after
> > bugging with this for whole day my mind is probably not really clear
> > anymore :)
> > My core was pure IPv4 before and after turning on MPLS I have few
> > strange problems. Current config (really short and stripped one) could
> > look like this (sorry for my ascii "art"):
> > CE1
> > |
> > PE1(c2811)
> > |
> > P1 (c7206vxr) -- PE2(c7401) -- CE2
> > |
> > P2 (gsr) -- P3 (gsr) -- PE3 -- CE3
> > |
> > P4 (gsr)
> >
> > All connections between CE's, PE's and P's are fastethernet or gigabitethernet
> > links, except between P2 and P4 where I have STM-1. I have also normal (ipv4)
> > clients connected to all PE and P's. Now I have some strange problem (at
> > least for me at this time of day). When I try to ping with 1500bytes/packet
> > (and DF bit set to 1) from any client it works fine from client (ipv4 client
> > not CE) all the way to P3. But when I try to ping P4 (over STM-1) it doesn't
> > go. When i set route-map which sets DF bit to 0 on ingress port from client to
> > my router it works (which is right anyway). Only problem I have with this is,
> > that I can't set those route-maps on every single ingress port I have all over
> > my network.
> > I would also understand this won't work if it would be constant all the way
> > through network, but not that only problem is on STM-1 link (with MTU set to 4470
> > bytes) while on ethernet links everything is working fine.
> > I would appreciate if someone can suggest some solution or at least tell me
> > it's normal that it doesn't work :)