ipv6: logging option docsis.cm-mac-address (4491 / 17 / 1026)

Benoit Panizzon benoit.panizzon at imp.ch
Fri Nov 23 14:02:16 UTC 2012

Hello World

The End Is Near (from IPv4 perspective).

So we are pushing IPv6 deployment.

A legal requirement is that we are able to tell which of our customers got 
which IPv6 address. Without this, we are not allowed to deploy IPv6 to the 
broadband end customers.

We use Arris CMTS and Modems. So far IPv6 for the hosts behind modems (still 
using IPv4 for provisioning) works in the lab.
But I was not able to have the cable modem mac address logged by the ISC DHCP 
Server. But this Mac Address is what we need to identify a customer.

Doing Traces of the IPv6 solicit messages, I see that the cm-mac-address 
vendor option is populated with the Cmac Address of the modems. So the info is 
there, I just need it to get logged.

My Code Snipplet:

Using: Internet Systems Consortium DHCP Server 4.2.3-P2

--- snip ---
option space docsis code width 2 length width 2 hash size 17;

option vsio.docsis code 4491 = encapsulate docsis;

option docsis.tftp-servers code 32 = array of ip6-address;
option docsis.cablelabs-configuration-file code 33 = text;
option docsis.device-id code 36 = string;
option docsis.time-servers code 37 = array of ip6-address;
option docsis.time-offset code 38 = signed integer 32;
option docsis.cm-mac-address code 1026 = string;

log (info, concat("*** LEMF *** Cable Mac: ", binary-to-
ascii(16,8,":",substring(option docsis.cm-mac-address, 16,6))));
--- snip ---

But this does noting at all.

A test with:
log (info, concat("LEMF Normal Lease: ", binary-to-
ascii(16,16,":",substring(option dhcp6.ia-na, 16, 16))));

Shows that logging basicly does work. It's not the substring statement that is 
wrong, I did try different lengths and even without it. If there is data in 
the option and the lengths are wrong, garbage is logged, but I just get noting 
at all.

Anyone spotting the error?

Kind regards

Benoit Panizzon
I m p r o W a r e   A G    -    

Zurlindenstrasse 29             Tel  +41 61 826 93 07
CH-4133 Pratteln                Fax  +41 61 826 93 02
Schweiz                         Web  http://www.imp.ch

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