From: Lord, Chris (chris.lord@lorien.co.uk)
Date: Sun Oct 10 2004 - 17:33:23 GMT-3
Thanks for putting me straight about this. Examination of the ospf database I think confirms your explaination.
Regards, Chris.
-----Original Message-----
From: Carlos G Mendioroz [mailto:tron@huapi.ba.ar]
Sent: 10 October 2004 13:13
To: Lord, Chris
Cc: ccielab@groupstudy.com
Subject: Re: ISDN Backup and OSPF Virtual Links
No, I think you don't neet that second VL.
R2-R3 may be physically down, but it's logically up.
R2 knows R3 info, and given the link is demand circuit, it keeps that
knowledge (DNA + no hellos). There are no 2 area 2 instances, only one.
Lord, Chris wrote:
> 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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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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