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New Member

Packet drop?

Hi,

I have a problem. Should unlabelled traffic get dropped by a router where MPLS is active on all interfaces ?

Thanks

3 REPLIES
Hall of Fame Super Silver

Re: Packet drop?

No,

unlabeled IP packets can be routed if there is a routing entry for them (or a default route).

Actually, in service provider networks to save labels (because the label space in a node is limited) the routers are configured with ACL that define for what IP prefixes labels have to be assigned.

In a service provider scenario using iBGP it is enough to have labels assigned for the loopback interfaces used as endpoints in iBGP sessions.

An example in old syntax is:

access-list 20 permit 10.240.0.0 0.0.3.255

no tag-switching advertise-tags

tag-switching advertise-tags for 20

this works if all loopbacks are in the allowed IP prefix

hope to help

giuslar

New Member

Re: Packet drop?

Interesting. Thanks!

But if the interface they are coming at is in a vrf and there is no route to destination in this vrf, shouldn't the router look in the global routing table by default ?

New Member

Re: Packet drop?

No by default it will do not look up in global routing table..This is how access to and from sites in a vpn are limited to only that VPN. There is way you can do this..by leaking the routes.

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