PE routers which attach to a particular VPN need to know, for each of that VPN's sites, which addresses in that VPN are at each site. There are several ways that a PE router can obtain this set of addresses. The Routing Information Protocol (RIP) sends routing update messages that include entry changes. The routing table is updated to reflect the new information. This functionality applies only to the 7450 ESS and 7750 SR.
RIP can be used as a PE/CE distribution technique. PE and CE routers may be RIP peers, and the CE may use RIP to tell the PE router the set of address prefixes which are reachable at the CE router's site. When RIP is configured in the CE, care must be taken to ensure that address prefixes from other sites (i.e., address prefixes learned by the CE router from the PE router) are never advertised to the PE. Specifically, if a PE router receives a VPN-IPv4 route, and as a result distributes an IPv4 route to a CE, then that route must not be distributed back from that CE's site to a PE router (either the same router or different routers).
In order to enable a VPRN RIP instance, the RIP protocol must be enabled in the config>service> >vprn>rip context of the VPRN. VPRN RIP is administratively enabled upon creation. Configuring other RIP commands and parameters are optional.
Careful planning is essential to implement commands that can affect the behavior of VPRN RIP global, group, and neighbor levels. Because the RIP commands are hierarchical, analyze the values that can disable features on a particular level.
The parameters configured on the VPRN RIP global level are inherited by the group and neighbor levels. Many of the 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 statement 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. There are no default VPRN RIP groups or neighbors. 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.
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)