I have a question about designing an OSPF network: suppose that I have two non backbone areas , for example areas 1 and 2, conected to backbone area 0.(normal behaviour).
And suppose that the network is geographically growing in a way that makes the two areas 1 and 2 adjacent. What would be the behaviour if I conect the two areas directly? (I would have an ABR between areas 1 and 2, and these areas are of course still conected to area 0).I am not sure about the fact that LSAs will still be transmitted through this ABR as summary LSAs...
In ospf its a must to have all area to be connected to backnone area to avoid the looping by using the distance vector behaviour exhibited by updates from the abr of backbone and non-backbone area.As above mentioned virtual link can be used to manipulate this..
I came across something called "Alternate ABR" which also modifies the abr behaviour and thus enabling two non-backbone area to be connected via router acting as abr..
think this is relevent to dicussion and would help
Yes if you have a router with interace(s) in area 1 and interface(s) in area 2 then you need a virtual link to make this router function as an ABR. While you could do 2 virtual links, you really only need 1. As long as the router is connected to area 0 once that is enough.