Open Shortest Path First (OSPF) - Router Alley
Open Shortest Path First (OSPF) - Router Alley
Open Shortest Path First (OSPF) - Router Alley
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<strong>OSPF</strong> v1.31 – Aaron Balchunas<br />
19<br />
<strong>OSPF</strong> Virtual Links (continued)<br />
It is also possible to have two separated (or discontiguous) Area 0’s. In order<br />
for <strong>OSPF</strong> to function properly, the two Area 0’s must be connected using a<br />
virtual link.<br />
Again, configuration occurs on the transit area’s ABRs:<br />
<strong>Router</strong>B(config)# router ospf 1<br />
<strong>Router</strong>B(config-router)# router-id 2.2.2.2<br />
<strong>Router</strong>B(config-router)# area 1 virtual-link 3.3.3.3<br />
<strong>Router</strong>C(config)# router ospf 1<br />
<strong>Router</strong>C(config-router)# router-id 3.3.3.3<br />
<strong>Router</strong>C(config-router)# area 1 virtual-link 2.2.2.2<br />
Always remember: the area specified in the virtual-link command is the<br />
transit area. Additionally, the transit area cannot be a stub area.<br />
As stated earlier, if authentication is enabled for Area 0, the same<br />
authentication must be configured on Virtual Links, as they are “extensions”<br />
of Area 0:<br />
<strong>Router</strong>B(config)# router ospf 1<br />
<strong>Router</strong>B(config-router)# area 1 virtual-link 3.3.3.3 message-digest-key 1 md5 MYKEY<br />
<strong>Router</strong>C(config)# router ospf 1<br />
<strong>Router</strong>C(config-router)# area 1 virtual-link 2.2.2.2 message-digest-key 1 md5 MYKEY<br />
* * *<br />
All original material copyright © 2007 by Aaron Balchunas (aaron@routeralley.com),<br />
unless otherwise noted. All other material copyright © of their respective owners.<br />
This material may be copied and used freely, but may not be altered or sold without the expressed written<br />
consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.