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MPLS Label Assignment

Hi,

Do cisco routers (10K,GSR,7500's) assign labels per vpn route ?

Can they assign label per vrf ?

The reason for this query is my concern of scalability when using Option B (RFC 4364 Sec 10.) as compared to Option C.

Thanks

Imran.

2 REPLIES
Silver

Re: MPLS Label Assignment

Inner Label is the vrf-label.

Thanks.

Re: MPLS Label Assignment

Hi,

there will be one label per prefix. Assigning a label for all routes in a VRF is not possible. The only option would be summarization to reduce the number of routes.

Be aware, that you have up to 1 Mio label available. So it is only then that you run out of labels. Not unlikely you run out of memory or CPU before that limit.

To get the maximum number of labels use the "mpls label range 16 1000000" command. By default there is a label range up to 100000 in all routers I know of.

As the label range is PER PE you in fact could have far beyond 1 Mio routes in your MPLS BGP without reaching a limit from the label space. Also not unlikely that you hit other resource limits (CPU, memory, bandwidth) much earlier.

When setting up Option B this all means that you need additional PEs once you learn more than 1 Mio customer routes from your peering PEs in the other AS.

Hope this helps! Please rate all posts.

Regards, Martin

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