OSPF - virtual link details (including configuration commands)

One 、ospf Introduction to virtual link ：

Virtual connection is between two ABR Between , Through a non backbone area （ Conversion area ——Transit Area）, A logical connection channel established , It can be understood as two ABR There is a point-to-point connection between .“ Logical channels ” It means two ABR Between multiple machines OSPF Of Router Just play a forwarding role message The role of （ Because the destination address of the protocol message is not these routers , So these messages are transparent to them , Just as normal IP Message to forward ）, Two sets of ABR Directly transfer routing information between . The routing information here refers to the routing information provided by ABR Generated type3 Of LSA, In the area Router The synchronization mode has not changed .

Two 、 Virtual connection （Virtual-link）：

Due to the complex topology of the network , Sometimes it is impossible to meet the requirement that each area must be directly connected with the backbone area , To solve this problem ,OSPF The concept of virtual link is proposed .

Virtual connection is set in two Router Between , Both routers have a port connected to the same non backbone area . Virtual connections are considered to belong to the backbone area , stay OSPF Routing protocol seems , Virtual connection between two ends Router By a Point to point Links are connected together . stay OSPF route Agreement , The routing information through virtual connection is regarded as the origin of intra domain routing .

3、 ... and 、 Command analysis ：

Router(config)#router ospf 100

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

•   stay OSPF Of Routing In configuration mode ,
•  Transit area-id ： Area number of conversion area
•  Router-id ： Virtual connection to the destination route ID
•   Two ABR All of them need to be configured .