Issue configuring static routes in MPLS VPN environment

[limtohsoon]

Hi Sir,

This is a simple question which I have doubts.

A CE router connects to a PE router on a GigE interface. Static routes are configured on the PE router to reach the customer networks, e.g.

ip route vrf Cust_A 10.10.10.0 255.255.255.0 Gig 2/1 10.1.1.2

ip route vrf Cust_A 10.10.20.0 255.255.255.0 Gig 2/1 10.1.1.2

.

.

and so on.

My question is, is it necessary to specify the egress interface when configuring the static routes? I have encountered cases whereby with the egress interface specified, the prefixes are correctly redistributed to other PE routers but traffic can't pass through - until I removed the egress interface from the static routes. In other cases, it works fine.

Please advise.

Thank you.

B.Rgds,

Lim TS

[swaroop.potdar]

Hi Lim,

It is not necessary to specify an outgoing interface in the static route. You can simply specify the next-hop IP address.

Now having said that both the methods can be used, but only condition to both is, if you use an interface as a next hop, then that interface has to be in the same VRF, or if you specify a next-hop IP the same has to be reachable within the same VRF.

There is a third method of static routes when you want to forward a specific VRF traffic to an next-hop not within any VRF.

Then you have to specify the global keyword in the end.

"ip route vrf global"

You may want to go through this link which explains all combinations of vrf static route commands available.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a008010437c.html#wp1047133

HTH-Cheers,

Swaroop

[limtohsoon]

Hi Swaroop,

Thanks for your reply.

In my case, both the outgoing interface and next-hop IP address are within the same VRF. Somehow, in certain cases it doesn't work.

Anyway, what's the impact of specifying the egress interface (in my case, GigE interface) and next-hop IP together? I don't practise pointing static route to broadcast media (e.g. Ethernet) for performance reason.

Thank you.

B.Rgds,

Lim TS

[swaroop.potdar]

When you say in some cases it doesnt work, it should be a configuration error. Since this is a very basic feature I havent come across any such known bugs.

Also there is no impact specifying the outgoing interface and the next-hop IP. It is always recommeded to specify the next-hop IP with outgoing interface since its a broadcast media.

Having said that you can simply omit the outgoing interface and specify the next hop ip only. For this you will have to do a redistibute connected into the IPV4 VRF address family. As the next-hop ip is a directly connected to your VRF.

HTH-Cheers,

Swaroop