Tuesday, October 6, 2009

Quiz: Multihomed Redundancy With Static Routes

Given scenario describes that CE1,CE2 and CE3 belongs to the same VPN and CE1 is multihomed with PE1 and PE2 router. Static routing is configured for CE 1 lan routes. When CE3 & CE2 desires to communicate with CE1 lan during that time the traffic of CE3 comes to PE2 and follow the back up link which customer doesnot want. The CE1 requirement is that everytime it's primary link should be used and secondary come into play when primary fails.
Post abstracts in comments or mail me directly shivludotjain at gmail dot com.

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Akinsola Oyelakin said...

I think if PE2 is using static route to CE1 then one hack will be to make the routes received from PE1 better than the static route.
To do this, we need to put admin distance on our static route on PE2

ip route vrf EXAMPLE 201
with the admin distance of 201, advertised routes from CE1 through PE1 to PE2 will be prefered over the static route.

Note: the routes have to be thesame (remember longest match wins regardless of admin distance)

GuruPrasad said...

In the Scenario, the Service Provider is a MPLS Cloud with Route-Reflector Enabled.

The MP-BGP session is enabled in the MPLS Cloud. To avoid CE3 communicate CE1 LAN Routes via the Back-up Link,

1. On the PE2 while advertising the Secondary Static Routes to the MPLS Cloud reduce the 'Local Preference to 90'. This way the LP value is lower than the default LP of 100.

2. Otherwise configure a Dynamic Routing Protocol on the PRY Link and increase the LP value of advertised Routes via PRY Link.

3. Lastly, configure Dynamic Routing Protocol on the PRY & SEC link and manipulate using Cost, Weight whichever is applicable.

Because increasing the Administrative Distance on the Secondary Link in-case of MP-BGP environment will not work because on the MP-BGP environment all redistributed routes will have equal AD of 200.

Hope I am informative.

Best Regards, Guru Prasad R