Thursday, April 16, 2009

Decrease The Label Database In Layer 2 MPLS

In my yesterday post I have covered how to provison a layer 2 mpls circuit. Today I am going to explain about implicit null label, a label which comes when the xconnect peer comes up. As per figure 1 check the mpls ldp binding table of PE-R1. A label for will be coming with implicit null. Now the question arises why it is coming so? Answer is so simple because when the ldp between the xconnect peer up, both treat them as directly connected to each other and advertise the directly connected interface with implicit null the same as in the case of PHP happens. But the label is never ever used for forwarding because when the packet reaches on R1-PE and the destination is for that it check the best IGP path and corresponding to that next hop is selected with outgoing label. So this implicit null will never be preferred in the case of layer 2 mpls vpn. These labels are only increasing the database and can be stopped by using acl.

step 1:- Create standard acl which will deny any thing
ip access-list 1 deny any

Step 2:- Bind the acl with the xconnect peer so that it won't accept any labels for IGP.
mpls ldp neighbor labels accept 1

The same command need to be configured at remote end peer also.

shivlu jain

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