3Com Switch 7700 Configuration Manual page 125

have a direct physical link with the backbone area 0.0.0.0, a virtual link must be
created.
If physical connectivity cannot be made due to network topology restrictions, a
virtual link can be used to meet the requirements of RFC 2328. The virtual link
refers to a logic channel set up through the area of a non-backbone internal route
between two ABRs. The two ends of the channel should be ABRs and the
connection can take effect only when both ends are configured. The virtual link is
identified by the ID of the remote router. The area, which provides the ends of the
virtual link with a non-backbone area internal route, is called the transit area. The
ID of the transit area should be specified during configuration.
The virtual link is activated after the route passing through the transit area is
calculated, which is equivalent to a P2P connection between two ends. Therefore,
similar to the physical interfaces, you can also configure various interface
parameters on this link, such as a hello timer.
The "logic channel" means that the multiple routers running OSPF between two
ABRs only take the role of packet forwarding (the destination addresses of the
protocol packets are not these routers, so these packets are transparent to them
and the routers forward them as common IP packets). The routing information is
directly transmitted between the two ABRs. The routing information refers to the
type-3 LSAs generated by the ABRs, for which the synchronization mode of the
routers in the area is not changed.
Perform the following configuration in OSPF area view.
Table 39 Configuring OSPF Virtual Link
Operation
Create and configure a virtual link
Remove the created virtual link
The area-id and router-id variables have no default value.
By default, the hello timer is 10 seconds, retransmit is 5 seconds, trans-delay is 1
second, and the dead timer is 40 seconds.
Configuring Summarization of Imported Routes by OSPF
The OSPF implementation in the Switch 7700 supports route summarization of
imported routes.
Perform the following configurations in OSPF view.
Table 40 Configuring Summarization of Imported Routes by OSPF
Operation
Configure summarization of imported routes
by OSPF
Remove summarization of routes imported
into OSPF
Command
vlink-peer router-id [ hello seconds |
retransmit seconds | trans-delay seconds |
dead seconds | simple password | md5 keyid
key ]*
undo vlink-peer router-id
Command
asbr-summary ip-address mask [
not-advertise | tag value ]
undo asbr-summary ip-address mask
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