https://tools.ietf.org/html/rfc3046

"

2.0 Relay Agent Information Option


The length N of the sub-options shall be the number of octets in only that sub-option's value field.  A sub-option length may be zero.

"

So you can have for example
Option 82  LEN 2 (sub options have total length 2 in total)
Suboption 2 LEN 0 (2 bytes) as above..

Or I may have read it all wrong..




From: jamie baddeley <jamie.baddeley@vpc.co.nz>
Date: Thu, 3 Apr 2014 22:37:23 +1300
To: Jonathan Brewer <jon.brewer@gmail.com>
Cc: "nznog@list.waikato.ac.nz" <nznog@list.waikato.ac.nz>
Subject: Re: [nznog] Bitstream 3a DHCP manipulation



On 3/04/2014, at 7:23 pm, Jonathan Brewer <jon.brewer@gmail.com> wrote:


On Thu, Apr 3, 2014 at 4:52 PM, Dave Mill <davemill@gmail.com> wrote:
I've obtained some pcaps from both ends and I can see the following changes occurring to a DHCP Request:

1) The transaction ID is changed
2) Option 82 is added. More specifically, sub-option 1 Agent Circuit ID is present and has a valid length. sub-option 2 Agent Remote ID is present, has a length of 0 and no content which wireshark doesn't seem to like much.

One would not expect an Ethernet service to be giving packets the bad touch.


Agree. To me this seems all wrong. Alarm bells are going off. 



_______________________________________________
NZNOG mailing list
NZNOG@list.waikato.ac.nz
http://list.waikato.ac.nz/mailman/listinfo/nznog
_______________________________________________ NZNOG mailing list NZNOG@list.waikato.ac.nz http://list.waikato.ac.nz/mailman/listinfo/nznog