H3C Technologies H3C S12500-X Series Switches - Manual (Page 140)

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Configuring inter-AS option A
Inter-AS option A applies to scenarios with a few VPNs.
To configure inter-AS option A, create VPN instances on PEs and ASBR-PEs. The VPN instances on PEs are
used to allow CEs to access the network, and the VPN instances on ASBR-PEs are used to access the peer
ASBR-PEs. An ASBR-PE considers the peer ASBR-PE as a CE.
The route targets configured on the PEs must match those configured on the ASBR-PEs in the same AS to
make sure VPN routes sent by the PEs (or ASBR-PEs) can be received by the ASBR-PEs (or PEs). Route
targets configured on the PEs in different ASs do not have such requirements.
For more information, see "
Configuring basic MPLS L3VPN ."
Configuring inter-AS option B
Inter-AS option B requires that ASBR-PEs maintain all VPNv4 routing information and advertise the
information to peer ASBR-PEs. The ASBR-PEs must receive all VPNv4 routing information without
performing route target-based filtering.
The route targets for the VPN instances on the PEs in different ASs must match for the same VPN.
An ASBR-PE always sets itself as the next hop of VPNv4 routes advertised to an MP-IBGP peer regardless
of the peer next-hop-local command.
ASBR-PEs use BGP to assign labels and create BGP LSPs. There is no need to configure MPLS LDP
between ASBR-PEs.
To configure inter-AS option B on an ASBR-PE:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view of the
interface connecting to the
remote ASBR-PE.
interface interface-type
interface-number
N/A
3. Configure the IP address of
the interface. ip address ip-address { mask |
mask-length }
N/A
4. Return to system view. quit N/A
5. Enter BGP view. bgp as-number N/A
6. Enter BGP-VPNv4 address
family view.
address-family vpnv4 N/A
7. 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.
Configuring inter-AS option C
To configure inter-AS option C, perform configurations on PEs and ASBR-PEs, and configure routing
policies on the ASBR-PEs.