Archive for the 'MPLS' Category

Selective export of routes in an MPLS VRF

Published on January 22, 2012 in MPLS and networking. 0 Comments

I need to be able to export just the public address from the route table inside a VRF, without impacting the existing route imports and exports

The existing VRF configuration is 

ip vrf blah
 rd 64512:12345
 route-target export 64512:1
 route-target import 64512:1

In this configuration all routes will be exported to all the other VRF’s that import 64512:1

The VRF has RFC1918 address space in it, but it also has some public IP address space that I need to be able to export to other VRF’s on the network.

After a bit of looking around, it appears the way to do this is to use the export map function, but there are a couple of catches. Firstly, you have to remove the other export statements, and you need bundle a number of match/set route maps together.

First create a couple of access lists

ip access-list standard rfc1918-address-space
 permit 10.0.0.0 0.255.255.255
ip access-list standard public-address-space
 permit 15.3.34.0 0.0.0.255

Now we need to create a route-map to set the exports based on the access lists.

route-map vrf-export-map permit 10
 match ip address rfc1918-address-space
 set extcommunity rt  64512:1
route-map vrf-export-map permit 20
 match ip address public-address-space
  set extcommunity rt 64512:1 64512:1001

The sequence 10 map, matches the rfc1918 address and adds an export of 64512:1 ( which is the existing export ). The sequence 20 map matches the public address space and adds 64512:1, and then also adds 64512:1001.

I think there is also an additive option – but I have not had time to look at it ( if I understand it correctly it address additional exports onto the current list of exports )

Now we just need to modify the VRF so that we pick up the route map.

ip vrf blah
 rd 64512:12345
 export map vrf-export-map
 route-target import 64512:1

You can now import the address space into multiple different VRF’s

This config will get all the address space

ip vrf blah2
 rd 64512:23456
 route-target import 64512:1

This config will just get the public address space

ip vrf blah3
 rd 64512:34567
 route-target import 64512:1001

Cheers
Pete