• After you have configured the route distinguisher, you can change it only by removing
and recreating the VRF.
• Example
host1:vr1(config-vrf)#rd 100:100
• There is no no version.
• See rd.
Defining Route Targets for VRFs
BGP uses an extended-community attribute, the route target, to filter appropriate VPN
routes into the correct VRFs. You configure the export list on the VRF to specify export
route targets. When BGP advertises a route from this VRF’s forwarding table, it associates
the list of export route targets with the route and includes this attribute in the update
message that advertises the route.
You also configure a route-target import list on each VRF to specify import route targets.
When a PE router receives a route, BGP compares the route target list associated with
the route (and carried in the update message) with the import list associated with each
VRF configured in the PE router.
For VPN-IPv4 routes received from another PE router, if any route target in the export list
matches a route target in a VRF’s import list, then the route is installed in that VRF’s
forwarding table.
For the most common configuration, do the following:
1. Allocate one route-target extended-community value per VPN.
2. Define the route-target import list and a route-target export list to include only the
route-target extended-community values for the VPN(s) to which the VRF belongs:
host1:vr1(config-vrf)#route-target export 777:100
host1:vr1(config-vrf)#route-target import 777:100
If the import and export lists are identical, you can use the both keyword to define
the lists simultaneously:
host1:vr1(config-vrf)#route-target both 777:105
A route-target export list can be modified on the sending PE router by an export map or
outbound routing policy. It can be modified on the receiving PE router by an import map
or inbound routing policy.
route-target
• Use to create—or add to—lists of VPN extended communities for a VRF that determine
whether a route is imported into a VRF.
• An export list defines a route-target extended community; routes having any route
target in their export list that matches a route target in a VRF’s import list are installed
in the VRF’s forwarding table.
425Copyright © 2010, Juniper Networks, Inc.
Chapter 6: Configuring BGP-MPLS Applications
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