Doug,
thanks for the reply - it finally clicked about 20 minutes after I posted.
what was confusing me I think is that the link is inter-area, whereas in
OSPF the ABR would be inter-area. the router can be inter-level, which I
though it couldn't, and the L1-L2 adjancency was confusing me as I thought
it was between a Level-1 and Level-2 interface which cannot be so.
think I was getting Level and Layer a bit mixed also ;-)
what I think I meant to draw out was:
RA------RB------RC------RF------RG
L1 L1/2 L2 L1/2 L1 - router-type
l1 l2 l2 l1 -
adjacency-type
\__area-x___/\__area-y__/\__area-z__/ - area
l1 l1+l2 l2 l1+l2 l1 - LS DB held
many thanks for your help - I think I'm there now
Andy
----- Original Message -----
From: "Doug Lockwood"
To:
Sent: Friday, June 01, 2001 6:29 AM
Subject: Re: IS-IS queries [7:6638]
> In your example, both RC and RE need to run both L1 and L2 processes.
> Doyle would refer to them as L1/L2 routers.
> So your second line would read:
>
> L1 L1 L1/L2 L2 L1/L2 L1 L1
>
> Since RD only connects to other routers that run L1/L2 SPF, it can choose
to
> be either L1 only, L2 only or both.
>
> RC and RE routers run 2 sets of SPF algorithms, one for L1 and another for
> L2.
>
> I also do not think L1 and L2 refer to Layer 1 and 2 of osi.
> I am told that this a very Decnet phase 4 view of the world.
> Think of L1 as within an area.
> Think of L2 as between areas. (or backbone routers)
> Think of L1/L2 as the ABR.
>
>
> "a router can only be a Layer1 *OR* a Layer2 router (or IS I
> suppose) for a particular area, right? "
>
> No. This is not correct. A router can run exactly 2 processes, an L1 and
> an L2 process.
>
> Feel free to drop me a line @ [EMAIL PROTECTED]
> or my [EMAIL PROTECTED] address, as well as the board.
>
> Good Luck
>
> Doug
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=6740&t=6638
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