MPLS VPN RIP
Table of Contents
Introduction
RIPv2 is one of the protocols that can be used between CE and PE.
MPLS RIPv2
- CE to PE support RIP as one of the dynamic routing protocols.
- Version 2 is supported.
- There are few features in MP-BGP that preserve protocol specific information that would be lost in redistribution, mainly the RIP metric.
- One feature is to preserver the RIP metric across the MPLS network by putting it in the MED attribute and during redistribution use that as the RIP metric. This helps in topologies when there are backdoor links (directly connected rip and mpls connected).
- MPLS VPN hop won't be considered as a RIP hop, so a metric of 0 will be maintained. While a backbone connection will add one hop.
- metric transparent- Causes RIP to use the routing table metric for redistributed routes as the RIP metric.
- IOS-XR will automatically redistribute metric transparently without any commends. This could be confusing at first, trying to find a command that doesn't exist.
- IOS-XR can have an issue if the directly connected interface is redistributed to BGP-MP. It will redistribute it with metric 0 and not accept it. This might have been changed in later version. I was not able to reproduce.
- Ways to fix the metric zero issue:
- Set the prefix with metric 1 using an RPL when redistributing BGP into RIP
- Use the command metric-accept-zero if available under the rip interface configuration mode.
- Set MED to 1 when redistributing RIP to BGP.
Relevant IOS Commands
redistribute bgp metric transparent
Copies the RIP metric from the other side of the mpls tunnel.
R6(congif)# router rip
R6(config-router)# address-family ipv4 vrf (Vrf)
R6(config-router-af)# redistribute bgp 100 metric transparent