Subject: RE: [Isis-wg] Help needed for ISIS error message in Cisco router

From: Anand Ammundi <[email-masked]>
Date: Fri, 20 Jul 2001 11:08:43 -0700

Amudha,
 it might be a bug on your box. basically it is a mismatch
 between the peers in terms of ethernet 2 and 802.3.
 ISIS is supported over 802.3. Depending on the value of the 
 type/len field one decides if it is ethernet 2 (type > 1500)
 or 802.3 (len < 1500) since ethernet 2 type's are always > 1500.
 since on the cisco the packet has come up as high as IS-IS (judging
 from the LAN Hello specific error), it has been assumed to be
 802.3...so if you have sent it as ethernet 2, you might see this
 error.
 	thanx
	anand

-----Original Message-----
From: Amudhavalli Narayanan [mailto:[email-masked]]
Sent: Friday, July 20, 2001 5:53 AM
To: [email-masked]
Subject: [Isis-wg] Help needed for ISIS error message in Cisco router

Hi,
We are trying an interoperability testing with Cisco. I get the following
error message in Cisco router when it receives packets from the router under
test
"%CLNS-3-BADPACKET: ISIS: LAN L1 hello, Packet(1500) or wire(1497) Length
invalid from 2101:0102:0304 (Ethernet 1/0).

It would be of great help, if someone can throw some light on this error
message.

Thanks,
Amudha

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From: Henk Smit <[email-masked]>
Date: Fri, 20 Jul 2001 12:31:09 -0700 (PDT)

The boundary between length and type encapsulation is not
 exactly at 1500 bytes. It is somewhere at 1600 or maybe 2000 bytes.
 (Can't remember). So it is very unlikely that in this case the
 receiving router is confused about the encapsulation.

  Also the error message says that the length value inside the
 ethernet header was 1497 (wire length). So this packet has
 definitely not been sent using length encapsulation.
 The error is that the ISIS stack that sent this packet has put
 the wrong value in the isisheader->packetlength field.

     henk.