3Com 8807 Configuration Manual page 545

Perform the following configuration in the OSPF view.
Table 537 Configure Domain ID
Operation
Configure Domain ID
Return to the default value
By default, id-number is 0 and id-addr is 0.0.0.0.
It is recommended that all OSPF instances in a VPN are configured with either the
same domain ID or the default value.
c
CAUTION: The configured value will not take effect unit the command reset ospf
is executed.
Step 3: Configure tag for imported VPN route (optional)
If a VPN Site links to multiple PEs, routing ring may present when the routes
learned by MPLS/BGP are received by another PE router in being advertised by
category-5/-7 LSA of a PE to the VPN Site. To solve this problem, you should
configure Route-tag. It is recommended to configure identical Route-tag for the
PEs in the same VPN.
Perform the following configuration in the OSPF view.
c
CAUTION: The configured Route-tag will not take effect unit the command reset
ospf is executed.
Table 538 Configure tag for imported VPN route
Operation
Configure tag for imported VPN route
Return to the default value
tag-number is used to identify Tag value; by default, the first two bytes are fixed,
that is, 0xD000, and the last two bytes is AS number of local BGP. For example,
the AS number of local BGP is 100, and then its default tag value is 3489661028
in decimal notation. This value is an integer ranging from 0 to 4294967295.
Step 4: Configure Sham-link (optional)
Sham-links are required between two PEs when Backdoor links (that is, the OSPF
links that do not pass through the MPLS backbone network) exist between the
two PEs and data is expected to be transported over the MPLS backbone. A
Sham-link between two PEs is considered as a link in OSPF domain. Its source and
destination addresses are both the Loopback interface address with 32-bit mask,
but this Loopback interface should be bound to a VPN instance and direct routes
must be imported into BGP by BGP. OSPF processes of the VPN cannot directly
import the routes of the Loopback interface (so the import direct command
cannot be executed in an OSPF processes of VPN); instead, an OSPF process can
only advertise the route indirectly by importing a BGP route.
Perform the following configuration in the OSPF area view.
BGP/MPLS VPN Configuration
Command
domain-id { id-number | id-addr }
undo domain-id
Command
route-tag tag-number
undo route-tag
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