Configuring inter-AS option B
To configure inter-AS option B, configure PEs and ASBRs.
PE configuration:
Configure basic MPLS L3VPN, and specify the ASBR in the same AS as an MP-IBGP peer. The route targets for the VPN instances on the PEs in different ASs must match for the same VPN. For more information about PE configuration, see "Configuring basic MPLS L3VPN."
ASBR configuration:
Configure a routing protocol, and enable MPLS and LDP on the interface connecting to an internal router of the AS.
Specify the PE in the same AS as an MP-IBGP peer, and the ASBR in a different AS as an MP-EBGP peer.
Disable VPN target filtering for VPNv4 routes so the ASBR can maintain all VPNv4 routes and advertise the routes to the peer ASBR.
Enable MPLS on the interface connected to the remote ASBRs. There is no need to configure a label distribution protocol, for example, MPLS LDP.
An ASBR always sets itself as the next hop of VPNv4 routes advertised to an MP-IBGP peer regardless of the peer next-hop-local command.
To configure inter-AS option B on an ASBR:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view of the interface connecting to the remote ASBR. | interface interface-type interface-number | N/A |
3. Enable MPLS on the interface. | mpls enable | By default, MPLS is disabled on the interface. |
4. Return to system view. | quit | N/A |
5. Enter BGP view. | bgp as-number | N/A |
6. Create a BGP peer. | peer { group-name | ip-address } as-number as-number | By default, no BGP peer is configured. Configure PEs in the same AS as IBGP peers, and ASBRs in different ASs as EBGP peers. |
7. Enter BGP VPNv4 address family view. | address-family vpnv4 | N/A |
8. Enable BGP to exchange VPNv4 routes with the PE in the same AS and the ASBR in different ASs. | peer { group-name | ip-address } enable | By default, BGP cannot exchange VPNv4 routing information with a peer. |
9. Disable route target based filtering of VPNv4 routes. | undo policy vpn-target | By default, the PE filters received VPNv4 routes by route targets. The routes surviving the filtering are added to the routing table, and the others are discarded. |