MPLS forwarding using FIB & LFIB
- To forward packets LSR uses:
- Both the FIB & LFIB hold
- necessary label information
- outgoing interface
- next-hop
- CEF FIB: Forward Information Base
- Used for incoming unlabeled packets.
- Router matches the packet's destination IP address to the best prefix in the FIB
- And forward the packet based on that entry.
- MPLS LFIB: Labeled Forward Information Base:
- Used for labeled packets.
- Router compares the label in the incoming packet to the LFIB's list of label
- and forward the packet based on that LFIB entry.
- Above image taken from Cisco press: ccie R&S certification guide, 4th edition
- MPLS enable forwarding process based on something other than the destination ip address such as:
- VPN from which the packet originated
- forwarding to balance traffic with traffic engineering
- & forwarding over different links based on QoS goals.
