[afnog] Problem bringing up MPLS on dissimilar interfaces

Mon Sep 22 20:31:00 UTC 2008

HI Frank,

I have a setup identical to yours which is working very well

P-R1#(config-subif)#do sh mpls ldp nei
    Peer LDP Ident: x.x.180.233:0; Local LDP Ident x.x.180.232:0
        TCP connection: x.x.180.233.39964 - x.x.180.232.646
        State: Oper; Msgs sent/rcvd: 239/298; Downstream
        Up time: 00:00:05
        LDP discovery sources:
          FastEthernet0/1.101, Src IP addr: x.x.180.154

PE-R1#sh mpls ldp neighbor 
    Peer LDP Ident: x.x.180.232:0; Local LDP Ident x.x.180.233:0
        TCP connection: x.x.180.232.646 - 41.220.180.233.39964
        State: Oper; Msgs sent/rcvd: 300/241; Downstream
        Up time: 00:02:06
        LDP discovery sources:
          GigabitEthernet0/2, Src IP addr: x.x..180.153
        Addresses bound to peer LDP Ident:

Can you replace mtu 1512 with mpls mtu 1512 on G0/1 and check you have no
access-list blocking LDP port 646 (common problem)
Hardcode your mpls router-id using mpls ldp router-id loopback0
It would also be good practice to run isis level on within same area (POPs)
using isis circit-type level-1 you can run level-1-2 or level-2 only on your
WAN links.
Finally I suggest you check that your IGP is working as desired and the
loopback ips are injected as isis level-1 routes.
NB. One point of note be very careful when redistributing as you may inject
unwanted routes I suggest to selectively inject the routes you need using a
route-map see below

router isis 
 net 49.0001.0000.0000.0001.00
 is-type level-1
 domain-password xxxxx
 area-password xxxxx
 redistribute connected metric 50 route-map redist-connected metric-type
external level-1
 redistribute static ip metric 50 route-map redist-static metric-type
external level-1

access-list 10 permit x.x.x.48 0.0.0.15
access-list 50 permit x.x.x.216 0.0.0.3

route-map redist-static permit 10
 match ip address 10
!
route-map redist-connected permit 10
 match ip address 50

and verify on originating router

sh ip route x.x.x.48
Routing entry for x.x.x.48/28
  Known via "static", distance 1, metric 0 (connected)
  Redistributing via isis
  Advertised by isis metric 50 metric-type external level-1 route-map
redist-static
  Routing Descriptor Blocks:
  * directly connected, via Serial2/1
      Route metric is 0, traffic share count is 1

As well as adjacent router

sh ip route x.x.x.48
Routing entry for x.x.x/28
  Known via "isis", distance 115, metric 124, type level-1
  Redistributing via isis
  Advertised by bgp xxxx
  Last update from x.x.x.97 on GigabitEthernet0/1, 13:47:05 ago
  Routing Descriptor Blocks:
  * x.x.x.97, from x.x.x.225, via GigabitEthernet0/1
      Route metric is 124, traffic share count is 1

HTH

Peter Nyamukusa - CCIP, JNCIS, MCSE 2000/2003. Linux+

-----Original Message-----
From: afnog-bounces at afnog.org [mailto:afnog-bounces at afnog.org] On Behalf Of
Frank A. Kuse
Sent: Monday, September 22, 2008 5:11 PM
To: mtinka at globaltransit.net
Cc: afnog at afnog.org
Subject: Re: [afnog] Problem bringing up MPLS on disimilar interfaces

Below are the requested parameters.

The show mpls ldp neighbor doesn't show anything.

Cisco 7200 NPE 400

interface Loopback0

 ip address 212.85.211.131 255.255.255.255

 ip router isis

interface FastEthernet0/0

 description Interface to P routers

 ip address 212.85.212.3 255.255.255.248

 duplex auto

 speed auto

 mpls label protocol ldp

 mpls ip

 mpls mtu 1512

router isis

 net 49.0001.0000.0000.0300.00

 redistribute static ip <be carefull here you can redistribute unwanted
routes and thus even cause a routing loop, any new static route is injected>

 passive-interface default

 no passive-interface FastEthernet0/0

 no passive-interface FastEthernet0/1

 no passive-interface FastEthernet2/0

 no passive-interface FastEthernet2/1

 no passive-interface Loopback0

Cisco 7200 NPE G1

interface Loopback0

 ip address 212.85.211.130 255.255.255.255

 ip router isis 

!

interface GigabitEthernet0/1

 description Interface to POPs

 mtu 1512 <Replace this mpls mtu 1512> 

 ip address 212.85.212.2 255.255.255.248

 duplex auto

 speed auto

 media-type rj45

 negotiation auto

 mpls label protocol ldp

 mpls ip

router isis 

 net 49.0001.0000.0000.0200.00

 passive-interface default

 no passive-interface GigabitEthernet0/1

 no passive-interface GigabitEthernet0/2

 no passive-interface GigabitEthernet0/3

 no passive-interface Loopback0

-----Original Message-----
From: Mark Tinka [mailto:mtinka at globaltransit.net] 
Sent: Saturday, September 20, 2008 11:55 AM
To: Frank A. Kuse
Cc: afnog at afnog.org
Subject: Re: [afnog] Problem bringing up MPLS on disimilar interfaces

On Saturday 20 September 2008 03:08:31 Frank A. Kuse wrote:

> I am having some trouble bringing up MPLS up on disimilar interfaces ( 
> FastEthernet Interface and Gigabit interface both connecting to a 
> cisco 3750 switch with Jumbo frames
> enabled)

Note that if these are Cisco routers, with the exception of the high-end kit
(i.e., 7600, XR 12000, CRS-1), Cisco don't generally support baby giant or
jumbo frames on their FE cards (although we are now seeing support for being
able to change the MTU on FE interfaces on the 7200 for much more recent
code).

> When i change the Gigabit interface to a FastEthernet interface, the 
> MPLS comes up.

Could we see some of your configurations on both routers (I'm assuming these
are Cisco)? If possible, can you send?

* sh run int <interface>
* sh int <interface>
* sh mpls interfaces
* sh mpls ldp neighbor

It'd be good to also look at your IGP configuration.

Recommend that you also have these commands by default in your global
configuration:

* mpls label protocol ldp
* mpls ldp router-id Loopback0

> I would like to know if it's possible to bring up MPLS up between two 
> disimilar interfaces.

It is possible - I've done it before.

Cheers,

Mark.

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