Only RIPv2 is supported

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Configuring RIP as the PE-CE routing protocol is even easier than configuring BGP. Start the configuration of individual routing context with the address-family ipv4 vrf vrf-name command in router configuration mode. You can enter all standard RIP parameters in the per-VRF routing context. Global RIP parameters entered in the scope of RIP router configuration are inherited by each routing context and can be overwritten if needed in each routing context.

Note Only RIPv2 is supported as the PE-CE routing protocol. It is good configuration practice to configure RIP version as a global RIP parameter using the version 2 command in router configuration mode.

Configuring RIP PE-CE Routing (Cont.)

RIP Metric Propagation

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Router(config)#

router rip

address-family ipv4 vrf vrf-name

redistribute bgp as-number metric transparent

• BGP routes must be redistributed back into RIP.

• The RIP hop count has to be manually set for routes redistributed

into RIP.

• For end-to-end RIP networks, the following applies:

- On the sending end, the RIP hop count is copied into the BGP

multi-exit discriminator attribute (default BGP behavior).

- On the receiving end, the metric transparent option copies

the BGP MED into the RIP hop count, resulting in a consistent

end-to-end RIP hop count.

• When you are using RIP with other protocols, the metric must be

manually set.

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The IGP metric is always copied into the multi-exit discriminator (MED) attribute of the BGP route when an IGP route is redistributed into BGP. Within standard BGP implementation, the MED attribute is used only as a route selection criterion. It is not copied back into the IGP metric. The IGP metric has to be specified in the redistribute command or by using the default-metric command in router configuration mode.

The MPLS VPN extension to the redistribute command (metric transparent option) allows the MED attribute to be inserted as the IGP metric of a route redistributed from BGP back into RIP. This extension gives transparent end-to-end (from the customer perspective) RIP routing:

■ By default, the RIP hop count is inserted into the BGP attribute MED when the RIP route is redistributed into BGP by the ingress PE router.

■ You can configure the value of the MED attribute (the original RIP hop count) to be copied into the RIP hop count when the BGP route is redistributed back into RIP. This action causes the whole MPLS VPN backbone to appear as a single hop to the CE routers.

Note You should not change the MED value within BGP if you use the redistribute metric transparent command.

Configuring RIP PE-CE Routing (Cont.)

The RIP configuration in this sample network is exceedingly simple:

■ The RIP routing process is configured. The RIP version is configured as the global RIP parameter.

■ The RIP routing context is configured for every VRF where you want to run RIP as the PE-CE routing protocol. The directly connected networks (configured on interfaces in the VRF) over which you want to run RIP are specified to have standard RIP configuration.

■ Redistribution from BGP into RIP with metric propagation is configured.

■ The BGP routing context is configured for every VRF. Redistribution of RIP routes into BGP has to be configured for every VRF for which you have configured the RIP routing context.

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