Subject: FW: [Isis-wg] Doubt

From: selvarajR <[email-masked]>
Date: Thu, 14 Sep 2000 15:31:46 +0530

Hi,
I was out of station for the past two days. So I couldn't reply imedietly 
Sorry.

If  adjacency with neighbours having same system Id as the local system be 
established then those neighbours won't get in the SPF tree construction.
Because local systems cost will be zero and hence the neighbour gets 
overridden. So no way the adjacency is usefull.
If there is no such validation then there will be a possibility that all IS 
on the LAN ( even whole domain)  having same system ID. Won't it be ?
So neighbours with conflicting SNPA and System ID be detected it can better 
be ignored. In any way it is NOT useful.

Having useless things is better not having it.

Selva.

-----Original Message-----
From:	[email-masked] [SMTP:[email-masked]]
Sent:	Tuesday, September 12, 2000 7:59 PM
To:	[email-masked]
Cc:	[email-masked]
Subject:	Re: [Isis-wg] Doubt

Hi Selva,

>I assume that, if any Hello PDU be received by an IS with system >Id same
as the received IS, then it can be discarded. ie Receiving >own hello PDU.

  I could not find reference to this in ISO 10589, where is this spelled
out? If they were not discarded, wouldn't the DR election process work
correctly?

> DOUBTS:
> 1. After DR election c1 , c2 and c4 will say c4 as the DR. But c3 >will
say c3 as the DR. So the  LAN will have more than one DR at a >time

  ISO 10589 states the following pertinent information in section 8.4.4 LAN
Designated Intermediate Systems:

d)After waiting ISISHelloTimer * 2 seconds, run the Level 1 and or the 
Level
2 Designated Intermediate System election process depending on the
Intermediate system type. This shall be run subsequently whenever an IIH 
PDU
is received or transmitted...(For these purposes, the transmission of the
system's own IIH PDU is equivalent to receiving it)...

   If IS-3 discards one of the IIH PDUs, I don't believe the DR election
process during circuit initialization will work properly. However,
subsequent DR elections should work properly because IS-3 will know about
both IIH PDUs being generated. Am I off in the weeds?

Cheers,
Ken Larmer
CommSense Networks

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