Ospf virtual link

A brief introduction

Virtual connection refers to a logical connection channel established between two ABR through a non-backbone area (transition region-Transit Area), which can be understood as a point-to-point connection between two ABR. " Logical channel "means that multiple routers running OSPF between two ABR only play the role of forwarding a message (because the destination address of the protocol message is not these routers, so these messages are transparent to them, they are only forwarded as ordinary IP messages), and routing information is transmitted directly between the two ABR. The routing information here refers to the LSA of the type3 generated by ABR, and the synchronization mode of the router in the area has not changed.

Virtual connection (Virtual-link): because of the complex topology of the network, sometimes it can not meet the requirement that each area must be directly connected to the backbone area. In order to solve this problem, OSPF put forward the concept of virtual link.

A virtual connection is set between two routers, both of which have a port connected to the same non-backbone area. Virtual connections are considered to belong to the backbone area. In the OSPF routing protocol, two routers at both ends of the virtual connection are connected by a point-to-point link. In OSPF routing protocol, routing information through virtual connections is treated as intra-domain routing.

Two orders

Router (config-router) # area area-id virtual-link router-id

1, in the routing configuration mode of OSPF

2, area-id: area code

3, Router-id: virtual connection to the destination routing ID

4. Configuration is required on both ABR.

Third, build the process

Build it on GNS3, and the topology diagram is shown below.

1 configure R4 as shown in the topology diagram

2 configure R1

3 configure R2

4 configure R3

5 configure two PCs

6. Build virtual links

7 test interworking