Configuring Ospf Sham Link - 3Com S7906E Configuration Manual

To do...
Enter BGP-VPNv4 subaddress
family view
Enable the exchange of
BGP-VPNv4 routing
information with a peer
Specify a BGP peer or peer
group as the UPE
Specify to advertise default
routes of a VPN instance to a
UPE
Specify to advertise routes
permitted by a specified routing
policy to a UPE
With the peer default-route-advertise vpn-instance command configured, the SPE always advertises
a default route using the local address as the next hop address to the UPE, regardless of whether the
default route is present in the local routing table or not.
The default routes of a VPN instance can be advertised to only a BGP peer or peer group that is
UPE.
It is not recommended to configure the peer default-route-advertise vpn-instance command and
the peer upe route-policy command at the same time.
It is not recommended for an SPE to be connected to a CE directly. If an SPE must be directly
connected with a CE, the VPN instance on the SPE and that on the UPE must be configured with
different RDs.

Configuring OSPF Sham Link

The sham link is considered an OSPF intra-area route. It is used to ensure that the VPN traffic is
transmitted over the backbone instead of the backdoor link between two CEs.
The source and destination addresses of the sham link must be loopback interface addresses with
32-bit masks. Besides, the loopback interfaces must be bound to the VPN instances and be advertised
through BGP.
Configuration Prerequisites
Before configuring OSPF sham link, be sure to complete these tasks:
Configuring basic MPLS L3VPN (OSPF is used between PE and CE)
Configuring OSPF in the LAN where CEs reside
Use the command...
ipv4-family vpnv4
peer { group-name |
ip-address } enable
peer { group-name |
ip-address } upe
peer { group-name |
ip-address }
default-route-advertise
vpn-instance
vpn-instance-name
peer { group-name |
ip-address } upe route-policy
route-policy-name export
1-41
Remarks
Required
Required
Required
Required
Configure either command.
By default, BGP does not
advertise default routes to a
VPNv4 peer.