Configuring Route-Target Filtering

To configure route-target filtering:

1. Enable the BGP routing process in the specified AS.

   The AS number identifies the PE router to other BGP routers.

   host1(config)#router bgp 738

2. Configure the peers for the BGP speaker. Use neighbor commands to specify the PE router peers to which BGP advertises routes and to configure any additional BGP attributes.

   host1(config-router)#neighbor 10.2.2.2 remote-as 45

   host1(config-router)#neighbor 10.2.2.2 update-source loopback 0

   host1(config-router)#neighbor 10.2.2.2 next-hop-self

3. Create the route-target address family to configure the router to use BGP signaling to exchange the RT-MEM-NLRI attribute with peer routers.

   Optionally, you can use the signaling keyword with the address-family command when you configure the route-target address family to specify BGP signaling of reachability information. Currently, you can omit the signaling keyword with no adverse effects.

   host1(config-router)#address-family route-target signaling

4. Activate the neighbors that routes of the route-target address family are exchanged with for this BGP session. The neighbors must first be created in the default IPv4 unicast address family.

   host1(config-router-af)#neighbor 10.2.2.2 activate

   host1(config-router-af)#neighbor 10.2.2.2 next-hop-self

5. (Optional) Configure BGP to send a Default-MEM-NLRI route for all peers in the address family or for a specific peer or peer group in the address family.

   host1(config-router-af)#default-information originate

   or

   host1(config-router-af)#neighbor 10.2.2.2 default-originate

6. Set the maximum number of received external BGP paths that can be accepted for route-target signaling.

   host1(config-router-af)#external-paths 2

7. Configure any additional address family parameters desired for the session.

external-paths

• Use to set the maximum number of received external BGP best paths allowed for route-target signaling.
• Specify a value in the range 1–255; the default value is 1.
• This command takes effect immediately; it does not bounce the session.
• This command applies to only the route-target address family.
• Example 1

  host1(config-router)#external-paths 45

• Example 2

  host1:vr1(config-router-af)#external-paths 45

• Use the no version to restore the default value, 1.
• See external-paths.

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