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