OSPF Virtual Links
185
F I G U R E 5 . 8
OSPF virtual link
Here is the configuration of RouterB and RouterC:
RouterB(config)#router ospf 10
RouterB(config-router)#network 3.0.0.0 0.255.255.255
area 0
RouterB(config-router)#network 4.0.0.0 0.255.255.255
area 10
RouterB(config-router)#area 10 virtual-link 6.6.6.1
where 10 is the Area ID of the transit area and where 6.6.6.1 is the highest
loopback address of the ABR joining the transit area to Area 20.
RouterC(config)#router ospf 10
RouterC(config-router)#network 4.0.0.0 0.255.255.255
area 10
RouterC(config-router)#network 7.0.0.0 0.255.255.255
area 20
RouterC(config-router)#area 10 virtual-link 5.5.5.1
where 10 is the Area ID of the transit area and where 5.5.5.1 is the highest
loopback address of the ABR joining the transit area to the backbone area.
RouterA
interface Loopback0
ip address 2.2.2.1 255.255.255.0
!
internet Ethernet0
ip address 1.1.1.1 255.255.255.0
!
Area 10
Area 0
e0
e1
e0
e1
e0
e1
Ethernet
Ethernet
RouterA
RouterB
RouterC
Area 20
1.1.1.1/24
3.3.3.1/24
3.3.3.2/24
4.4.4.1/24
4.4.4.2/24
7.7.7.1/24
Lo0:6.6.6.1/24
Lo0:5.5.5.1/24
Lo0:2.2.2.1/24
Virtual Link
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