[j-nsp] Strange IS-IS Problem

Stefan Fouant sfouant at shortestpathfirst.net
Mon Mar 8 13:00:07 EST 2010


One thing to add - you are probably already aware of this, but the family inet MTU won't have any bearing on those CLNS frames - have you tried either setting a physical MTU or a family iso MTU at something much lower?  I'd even try an MTU size of 1400 just to completely rule that out.

Stefan Fouant
Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Eric Van Tol <eric at atlantech.net>
Date: Mon, 8 Mar 2010 11:57:55 
To: Jonathan Looney<jonlooney at gmail.com>
Cc: Juniper-Nsp<juniper-nsp at puck.nether.net>
Subject: Re: [j-nsp] Strange IS-IS Problem

Both MTUs are consistent and always have been.  I started out with 9216 physical MTU and 1500 inet MTU, but have since just deleted the custom MTU and went with the defaults.  I am quite sure now that this is not an MTU issue, but rather a deficiency with the EX2500.  I've opened up a JTAC case and will let the list know what the problem turns out to be.

-evt

From: Jonathan Looney [mailto:jonlooney at gmail.com]
Sent: Monday, March 08, 2010 10:57 AM
To: Eric Van Tol
Cc: Juniper-Nsp
Subject: Re: [j-nsp] Strange IS-IS Problem


On Sun, Mar 7, 2010 at 8:04 AM, Stefan Fouant <sfouant at shortestpathfirst.net<mailto:sfouant at shortestpathfirst.net>> wrote:
I could be wrong but if I recall correctly the Hello PDU uses a padding TLV to pad the initial hello to the maximum MTU size.  I don't believe these packets are fragmentable if I recall considering it's a CLNS frame, i.e. no IP header and thus no fragment options.



This is also my understanding.  And, this makes me think that you really should make the MTUs on both sides consistent before you try to troubleshoot anything else.

-Jon
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