how to change the path of MPLS

r.chung · ‎04-21-2007

How to change the path of MPLS core from one PE to the other PE with redundancy link? The IGP is OSPF and running MBGP among PE routers.

mohammedmahmoud · ‎04-21-2007

Hi there,

Load-balancing is applicable in MPLS as follows:

If multiple equal-cost paths exist for an IPv4 prefix, the Cisco IOS can load-balance labeled packets. If labeled packets are load-balanced, they can have the same outgoing labels, but they can also be different. The outgoing labels are the same if the two links are between a pair of routers and both links belong to the platform label space. If multiple next-hop LSRs exist, the outgoing label for each path is usually different, because the next-hop LSRs assign labels independently.

If a prefix is reachable via a mix of labeled and unlabeled (IP) paths, Cisco IOS does not consider the unlabeled paths for load-balancing labeled packets. (The load balancing is done only between labeled paths. This means that if an IP (unlabeled) and a labeled path have the same cost, only the labeled path is used to forward the packets.)

HTH,

Mohammed Mahmoud.

jayjorda · ‎04-21-2007

If these redundant paths are not equal costs, then MPLS is going to use the path that the IGP determined to be the shortest. MPLS itself makes no path selection. It depends on the IGP to determine that. So if you want to use a different path, you will have to change the IGP metrics so the IGP picks a different path, or use MPLS Traffic Engineering.

Jay