Cisco CCNA Study Guide - Router Alley

CCNA Study Guide v2.62 – Aaron Balchunas
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OSPF Virtual Links (continued)
It is also possible to have two separated (or discontiguous) Area 0’s. In order
for OSPF to function properly, the two Area 0’s must be connected using a
virtual link.
Again, configuration occurs on the transit area’s ABRs:
RouterB(config)# router ospf 1
RouterB(config-router)# router-id 2.2.2.2
RouterB(config-router)# area 1 virtual-link 3.3.3.3
RouterC(config)# router ospf 1
RouterC(config-router)# router-id 3.3.3.3
RouterC(config-router)# area 1 virtual-link 2.2.2.2
Always remember: the area specified in the virtual-link command is the
transit area. Additionally, the transit area cannot be a stub area.
As stated earlier, if authentication is enabled for Area 0, the same
authentication must be configured on Virtual Links, as they are “extensions”
of Area 0:
RouterB(config)# router ospf 1
RouterB(config-router)# area 1 virtual-link 3.3.3.3 message-digest-key 1 md5 MYKEY
RouterC(config)# router ospf 1
RouterC(config-router)# area 1 virtual-link 2.2.2.2 message-digest-key 1 md5 MYKEY
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