mpls LIB & LFIB

[difyang]

1. Ps advise the difference between LIB and LFIB?

2. if un-labeled packet, will P router do normal ip routing, assume it's in FIB entry?

3. for CEF, if no entry in FIB, how to deal with the packet?

thanks

difei

[mazhar71]

Hi,

I will try to explain as I can:

1-LIB is the table which holds all prefxes & labels from all the neigbors

LFIB is the table which is used forwarding & holds incoming & outgoing label for a prefix for the best path(s).

2-When a packet comes without a label , this will always tried to be sent by using routing table (actually switching using FIB.)

3- CEF table is created from routing table & updated when a change occurs on the routing table before packet forwarding. So there should be always a match for the prefix as soon as there is a route for the prefix on the routing table.

Regards

[difyang]

hi,

so LIB should be funation at control plane while LFIB works at data plane.

thanks! difei

[jsyed]

Hi,

1. FIB stands for forwarding information base, where LFIB stands for label forwarding inforamtion base also called TFIB in older cisco documentation

2. if its unlabel then it will do normal IGP routing ( at ingress it will drop the packet if it is corrupt or no entry is found in table) . If packet has an entry in FIB then it must have FEC. FIB classifies packet with FEC (forwarding equivalence class to do label look up in MPLS back bone.

3. if no entry in CEF routing table then it will drop the packet.

hope this helps

javed