untagged prefixes...

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Feb 19th, 2010
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read following on two forums:


Reference I

Untagged Label:- Untagged label in the LFIB when the IP prefix is a directly connected interface, a summary route or the next-hop router has not advertised the label.

http://www.mplsvpn.info/2009/03/untagged-labels-coming-instead-of-pop.html


Reference II............

Summary: you would see the Untagged label in the LFIB when the IP prefix is a directly connected interface, a summary route or the next-hop router has not advertised the label.




As per my understanding:

LFIB doesnot contain directly connected prefixes, since the local router requests a POP action from its adjacent LDP neighbors for directly connected prefixes.

Therefore it does not receive a labeled packet for directly connected prefixes and does not have have to lookup in LFIB for them..



Regards,

MukarraM

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Laurent Aubert Fri, 02/19/2010 - 13:45
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Correct. Also an implicit null label will be associated to any summary routes. So the only case where you should see "untagged label" should be when you allocated a label to a prefix and you never received one from the downstream peer.


HTH


Laurent.

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