From: Lord, Chris (chris.lord@lorien.co.uk)
Date: Sun Oct 10 2004 - 07:00:06 GMT-3
I have the following scenario......
R2----FR1---R1----FR2-----R3--Ethe
R2----------ISDN--------------R3
The FR link between R1 and R2 is in ospf area 0
The FR link between R1 and R3 plus the R3 ethernet are all in area 1
The ISDN link is in area 2
(the frame relay links are independant i.e. not hub-and-spoke)
The ISDN is being used to backup the R1-R3 FR2 link and I am using demand circuit.
Hope this makes sense so far!
My question is what virtual links do I need??
Obviously I need a VL between R2 and R3 (isdn link) because when the FR2 goes down area 1 becomes an isolated area on R3 ethernet.
But, do I also need a VL between R1 and R3 for normal conditions? My logic is this... under normal conditions, the bri interfaces are up but the ISDN is down, so, we have two area 3s - one on the R3 bri intf and a second on the R2 bri intf - but unconnected. So under normal circumstances Area 3 on the R3 bri intf is isolated from the backbone area 0.
In practice I don't think it makes any difference to the functioning of the network whether there is a VL between R1 and R3 or not. However, for the exam, is it good practice to do so??
What d'ya think?
TIA
Chris
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