One of the things that I think it must be stuck in the mind of everyone who works in the field of networks is how to setup the Virtual Link in the OSPF and the consideration of the fact that the subject is very important album will present it to keep the subject as a reference to any one of us
What is the Virtual Link?
As is well known OSPF protocol that allows the division of the network into several domains Area, but the important thing required is that they should be all domains directly connected with the Physically Area zero or Backbone Area
As we see hier all Areas are directly connected with the Physically Area zero or Backbone Area.
but Look hier what about Area 2 (special case)
as we see Area 2 is not connected with Area zero thus there will be no contact between A0 and A2 and no exchange of the Routing Table what is the solution?
Solution offered by OSPF for us to solve this problem is Virtual Link is clear from the name that will create a Virtual connection passes through the non-backbone area
in our previous example Area one and communicates with Area zero and achieves the condition demanded by the OSPF that there should be direct contact with Area 0
there are with Another benefit when we use Vitual Link , if we want to we connect 2 Backbone Area with each other to work together such as one Backbone or you can use the Backbone II as A backup Area or better to say Redundancy Backbone in case something happens with the router, which represents the main Backbone. Look Down
its simplest thing to config, only two lines of commands on each router to take this example.
Please note that the written IP is the Router-id for OSPF
A final word or note I would like to attach it is necessary to make sure of the type of Area, because they transport but if the Area is Stub Areaa the method will be not work.