PE routers attached to a specific VPN must learn the set of addresses for each site in that VPN. There are several ways for a PE router to obtain this information, one of which is the Routing Information Protocol (RIP). RIP sends routing update messages that include entry changes to the routing table, which is updated with the new information.
RIP can be used as a PE/CE distribution technique. PE and CE routers can be configured as RIP peers, and the CE router can transmit RIP updates to inform the PE router about the set of address prefixes which are reachable at the CE router's site. When RIP is configured in the CE router, care must be taken to ensure that address prefixes from other sites (address prefixes learned by the CE router from the PE router) are never advertised to the PE router. Specifically, if a PE router receives a VPN-IPv4 route and, as a result, distributes an IPv4 route to a CE router, then that route must not be distributed back from that CE's site to a PE router (either the same router or different routers).
To enable a VPRN RIP instance, enable the RIP protocol in the config>service> >vprn>rip context of the VPRN. VPRN RIP is administratively enabled upon creation. Configuring other RIP commands and parameters is optional.
The parameters configured at the VPRN RIP global level are inherited by the group and neighbor levels. Several hierarchical VPRN RIP commands can be modified on different levels; the most specific value is used. That is, a VPRN RIP group-specific command takes precedence over a global VPRN RIP command. A neighbor-specific command takes precedence over a global VPRN RIP and group-specific command. For example, if you modify a VPRN RIP neighbor-level command default, the new value takes precedence over VPRN RIP group- and global-level settings. VPRN RIP groups and neighbors are not created by default. Each VPRN RIP group and neighbor must be explicitly configured.
The minimal parameters that should be configured for a VPRN instance are:
Specify a VPRN RIP peer group.
Specify a VPRN RIP neighbor with which to peer.
Specify a VPRN RIP peer-AS that is associated with the above peer.
The VPRN RIP command hierarchy consists of three levels:
the global level
the group level
the neighbor level
For example:
config>service>vprn>rip# (global level)
— group (group level)
— neighbor (neighbor level)