06-30-2025 12:08 PM - edited 06-30-2025 12:08 PM
Hello all,
I'm trying to determine the exact order of operations a router takes when you run mpls ip on the router, specifically when/how the router builds the LFIB table.
The first step I have is that the router takes all the routes in the RIB and assigns a label to each non-/32 route (label numbers start at 16 and go up), and the router puts these "labeled routes" in a new table called the LIB (Label Information Base).
Once the router builds the LIB table, the router builds the LFIB table, but I'm not sure how - I've read two methods:
So, is the LFIB built from the RIB/LIB combination, or is the LFIB built from the FIB label entries?
Thanks again!
06-30-2025 12:42 PM - edited 07-02-2025 09:17 AM
Fib is same as rib except fib is for data plane and rib is for control plane
Same as lib and lfib.
MHM
06-30-2025 12:45 PM
I couldn't (at least quickly) find the answer to your question.
For general (and dated?) Cisco IOS operations, you'll normally find variants of: https://www.slideshare.net/slideshow/cisco-ios-order-of-operation/16372702 or https://blog.router-switch.com/2013/01/whats-the-order-of-operations-for-cisco-ios/.
Neither of which, unfortunately, mention MPLS.
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