OSPF Areo 0 and Virtual links

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Sep 26th, 2008
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guys basic question abt ospf virtual links.....for exaple three routers are connected A,B,C And B router serials are connected and are in areo the fethernet of the routers are in area 10 so do we need virtual connection to area 0 or not if yes why if not why??? whats the rule of thumb for virtual links......

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Jon Marshall Fri, 09/26/2008 - 05:41
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In OSPF all areas in the same AS must be physically connected to area 0 so a router (ABR - Area Border Router) that connects area 0 to area 10 for example would have at least one interface in area 0 and one interface in area 10.


Virtual links are used when there is no physical connection to area 0. See this attached doc for more details


http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094aaa.shtml#virtuallinks


Note that virtual links are not good design. They are usually used as a temporary stop gap.


Jon

paul.matthews Fri, 09/26/2008 - 06:30
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Your question is not totally clear. The basic OSPF rule is that all areas shall be connected to the backbone. If you have an area that does not have a direct connection to the backbone, to allow connectivity to other areas you would need to configure a virtual link.


The rule of thumb for virtual links? They are for emergencies, temporary use or for people that cannot design networks.

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