Why Link-State Routing Protocol for MPLS

[sushilpandita78]

why do we have to use a Link-State Routing Protocol only like OSPF or ISIS for running MPLS in a service Provider Network.Why don't we use RIP-V2 or IGRP or EIGRP .are there any particular reasons for which we have to use Link-State Routing Protocols only.

[lee.reade]

Hi,

If you are only going to deploy MPLS VPNs then you can use any routing protocol you wish, but if you want to deploy MPLS Traffic Engineering, then this feature requries that link state information, which includes available bandwidth on all links is flooded throughout the network.

In order to do MPLS TE you must use either OSPF or ISIS.

HTH

LR

[Giuseppe Larosa]

Hello Sushil,

the reasons for using OSPF or IS-IS is that are the only ones to support MPLS Traffic Engineering.

If you don't use MPLS TE you can use EIGRP or RIPv2 to provide MPLS VPN service.

But if in the future you wish to use MPLS TE you need to change IGP

You cannot use RIPv1 or IGRP because they don't carry the subnet mask in their updates (classful old distance vector protocol)

While LDP carries the subnet mask.

For MPLS to work LDP subnet mask must be equal to routing protocol advertised mask for the same subnet.

give a look at mpls overview

http://www.cisco.com/en/US/docs/ios/12_2/switch/configuration/guide/xcftagov_ps1835_TSD_Products_Configuration_Guide_Chapter.html

Hope to help

Giuseppe