[j-nsp] Strange IS-IS Problem

[Eric Van Tol]

> -----Original Message-----
> From: Stefan Fouant [mailto:sfouant at shortestpathfirst.net]
> Sent: Sunday, March 07, 2010 8:04 AM
> To: Eric Van Tol; juniper-nsp-bounces at puck.nether.net; Derick Winkworth;
> Juniper-Nsp
> Subject: Re: [j-nsp] Strange IS-IS Problem
> 
> 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.

But if I can push through a baby giant packet without even configuring anything, wouldn't that mean that large packets are allowed through?

> 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.

I checked the various counter stats and could not find any errors on any of the ports.  In fact, I see this:

Received valid L2 unicast packets:  18473
Received valid IPv4 unicast packets:  18473
Received valid L2 multicast packets:  123024
Received valid non-IP multicast packets:  123000
Received valid IPv4 multicast packets:  24
Received 64 byte packets:  23
Received 65-127 byte packets:  123032
Received 128-255 byte packets:  1
Received 1024-1522 byte packets:  8393
Received 1523-2047 byte packets:  10048
Received octets:  48192973
Received octets in valid non-IP packets:  15127879
Received octets in valid IPv4 packets:  33065094

As an aside, it appears that OSPF works fine if I set that up.  Not a long term solution, though.  I do believe that you are on to something, though.  Unfortunately, I can't see anywhere to configure the EX2500 ports to accept specific ethertypes.

Does anyone else have ISIS running _through_ an EX2500?

> Stefan Fouant

-evt
> ------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
> 
> 
> 
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
> 
> 
> Sent from my Verizon Wireless BlackBerry