3Com 10014299 manual Create and Configuring a Virtual Link, Area-id None Router-id None

Configuring OSPF 435

The virtual link is activated after the route through the transit area is calculated. It is equivalent to a point-to-point connection between two terminals. Parameters can be configured for this connection like a physical interface, such as sending a hello-timer.

A “logic channel” is provided for multiple routers running OSPF that forwards messages between two ABRs. Since the destination addresses of the protocol messages are not these ABRs, the messages are transparent to them and they are transmitted as ordinary IP messages, while routing information is transmitted directly between the two ABRs. Routing information here means an LSA of Type3 that is generated by ABR. The synchronization of routers in the area is not changed.

When configuring a backbone area, note that:

■The backbone area is responsible for advertising the routing information of the non-backbone area. If the AS is divided into more than one area, one area must be the backbone area, and other areas must be connected with the backbone area directly or logically.

■The backbone area must include all ABRs, and may include routers belonging to the backbone area only. An ASBR may not be inside the backbone area.

■ABRs inside the backbone area must be well connected, and may be connected physically or logically (establishing virtual connection between ABRs).

When configuring a virtual connection, note that:

■A virtual connection can only span one area, which means that the non-backbone area can establish virtual connection with the backbone area only by spanning one other non-backbone area.

■Multiple virtual connections can be connected in series to form a new virtual connection.

Perform the following configurations in OSPF view.

Table 501 Create and Configuring a Virtual Link

Operation	Command
Create and configure a virtual link	vlink peer-id router-idtransit-area
	area-id[ hello-timer seconds ] [
	retransmit-timer seconds ] [
	transit-delay seconds ] [ dead-timer
	seconds ]
Delete the specified virtual link	undo vlink peer-id router-id
	transit-area area-id

By default, there is no virtual link is created. The attributes for this command have the following default values:

■area-id : None

■router-id : None

■hello-timer: 10 seconds

■retransmit-timer: 5 seconds

■transit-delay:1 second