Issue with MPLS label at ingress router

Unanswered Question
Oct 4th, 2007

I have a PE where I have to putting

" mpls static binding ipv4 "command other wise label not generating .

Can isolate where actually issue.

I have this problem too.
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swaroop.potdar Fri, 10/05/2007 - 06:05

Sanjoy, can you elaborate the issue further...

why you have to use IPV4 binding and isnt the route there in IGP (as LDP should generate bindings for all routes in the IGP).



sanjoy2006 Fri, 10/05/2007 - 12:38

Hi Swaroop,

My igp unicust routing working properly still now no lebel initite ,I have to mapped static

vishalpreenja Fri, 10/05/2007 - 11:32

With a regular binding, labels are randomly assigned.

Static bindings between labels and IPv4 prefixes need to be configured to support MPLS hop-by-hop forwarding through neighbor routers that do not implement LDP label distribution. May be LDP distribution is not configured in your case.

Rajesh Sir : Plz verify

swaroop.potdar Fri, 10/05/2007 - 14:53

Sanjoy, is there LDP enabled for label distribution, as I dont see a reason why you should not have labels with LDP being there with the routes present in the IGP, unitll and unless there is a acl based filter prohibiting it. what is the protocol you are predominatly using for label distrbution in you network.


Although the label values are randomly asigned you can still configure a range for the labels to be assigned from using the mpls label range command.

And even if the label assignment is random, it shouldnt be any problem for operations, as you seldom have to look at a label value beyond a router itself.

Is your network consisting of 2 islands where each entity is running a different label distrbution protocol?



william.caban Sun, 10/07/2007 - 15:00

Did you have "ip cef" disabled in the router? It is about the only time when I've seen this.

Also, if your PE is an old router try upgrading the IOS image. This can be more a bug issue than a configuration issue.

sanjoy2006 Tue, 10/09/2007 - 01:43

Ya , I am susspecting the same will degarde the IOS because there is ADVENT image .

william.caban Tue, 10/09/2007 - 07:40

For carrier I will recommend the advip feature set instead of the advent. Having unnecessary enterprise features on a carrier or ISP increase the possibility of hitting more bugs.

swaroop.potdar Tue, 10/09/2007 - 09:31

Sanjoy, William,

I really doubt that it would be a bug, as label assignment is a very preliminary function. Unless we are missing something else somewhere.



william.caban Tue, 10/09/2007 - 10:27

Well, I know by a fact, there are such bugs in older images. (Now, I don't know if that is the case here).

I've seen this problem in the 3640 with the following IOS and specs:


3640 12.0(25)S 64MB

In this particular image, you may have an ASBR receiving labels but it stop to generate labels, or you can see routes being advertised as untagged when they are being received as tagged.

It usually get fixed with "no ip cef" and then "ip cef" or shutdown the interface and enabling it again. In some instances, I have to reboot them (...and this has happened with any of the 12 of these I have used for MPLS labs)

But also, as you mention, we might not have the whole picture here.

sanjoy2006 Fri, 10/12/2007 - 07:14

Willam Swaroop ,

Can't use advip because it's not support Xconnect for L2tpv3

swaroop.potdar Fri, 10/12/2007 - 08:41

Sanjoy, to take the issue conclusively further, rather than upgrading the IOS can you give the outputs below.

1) show runn mpls ldp

2) show route

3) show mpls ldp bindings

4) show mpls forwarding




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