[j-nsp] Strange IS-IS Problem

[Stefan Fouant]

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.  I think it's already been said but the fact that you are using jumbo frames and also because you are using EX 2500s (not native JUNOS) makes it extremely suspect that you are likely running into some form of MTU issue.

One other thing you might want to check on the EX 2500 - interface counters - look for L2 Channel errors or other inconsistencies which might indicate the EX doesn't recognize the Ethertype, etc.

Stefan Fouant
------Original Message------
From: Eric Van Tol
Sender: juniper-nsp-bounces at puck.nether.net
To: Derick Winkworth
To: Juniper-Nsp
Subject: Re: [j-nsp] Strange IS-IS Problem
Sent: Mar 7, 2010 4:42 AM

> From: Derick Winkworth [mailto:dwinkworth at att.net] 
> Sent: Sunday, March 07, 2010 1:26 AM
> To: Eric Van Tol; Juniper-Nsp
> Subject: Re: [j-nsp] Strange IS-IS Problem
> 
> If its JUNOS, then just configure the MTU normally in the interface
> config on the switch.

It does not run JUNOS and there is no config option for MTU that I can find.  I don't believe that it's configurable, but it "just works".  Without configuring anything on the EX2500, I was able to pass 2000-byte sized IP packets between the Junipers.

-evt



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