Alcatel Carrier Internetworking Solutions 060187-10 REV D manual Creating Virtual Links

Configuring OSPF Configuring OSPF

Creating Virtual Links

A virtual link is a link between two backbones through a transit area. Use the ip ospf virtual-linkcommand to create or delete a virtual link.

Accepted network design theory states that virtual links are the option of last resort. For more information on virtual links, see “Virtual Links” on page 1-10and refer to the figure on page 1-10.

Creating a Virtual Link

To create a virtual link, commands must be submitted to the routers at both ends of the link. The router being configured should point to the other end of the link, and both routers must have a common area.

When entering the ip ospf virtual-linkcommand, it is necessary to enter the Router ID of the far end of the link, and the area ID that both ends of the link share.

For example, a virtual link needs to be created between Router A (router ID 1.1.1.1) and Router B (router ID 2.2.2.2). We must:

1Establish a transit area between the two routers using the commands discussed in “Creating an OSPF Area” on page 1-18(in this example, we will use Area 0.0.0.1).

2Then use the ip ospf virtual-linkcommand on Router A as shown:

ip ospf virtual-link 0.0.0.1 2.2.2.2

3Next, enter the following command on Router B:

ip ospf virtual-link 0.0.0.1 1.1.1.1

Now there is a virtual link across Area 0.0.0.1 linking Router A and Router B.

4To display virtual links configured on a router, enter the following show command:

show ip ospf virtual-link

5To delete a virtual link, enter the ip ospf virtual-linkcommand with the area and far end router infor- mation, as shown:

no ip ospf virtual-link 0.0.0.1 2.2.2.2

Modifying Virtual Link Parameters

There are several parameters for a virtual link (such as authentication type and cost) that can be modified at the time of the link creation. They are described in the ip ospf virtual-linkcommand description.These parameters are identical in function to their counterparts in the section “Modifying Interface Parameters” on page 1-24.

OmniSwitch 6600 Family Advanced Routing Configuration Guide March 2005 page 1-25