Option dhcp6.client-linklayer-addr

perl-list perl-list at network1.net
Tue Feb 3 20:41:27 UTC 2015

Wireshark shows option 79 clearly present in the packet. Looks like the mac address of the device is e4:11:5b:29:e4:35 

It does indeed look like RFC 6939 OPTION_CLIENT_LINKLAYER_ADDR (79) should be in 4.3.1 per https://deepthought.isc.org/article/AA-01112/0/Newly-Pre-defined-Options-in-DHCP-4.3.html 
dhcp6.client-linklayer-addr string 
A client link-layer address. The first two bytes must be the type of the link-layer followed by the address itself. 
This option is included based on RFC 6939. 

Hope this gets resolved as we will need to use that option in the future. 

Out of curiosity, Antonios, what relay agent are you using that is adding that option to the packet? 

> From: "Antonios Atlasis" <antonios.atlasis at gmail.com>
> To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> Sent: Tuesday, February 3, 2015 2:48:35 PM
> Subject: Re: Option dhcp6.client-linklayer-addr

> Thank you very much Espen for your response.

> Well,. the client linklayer address option is not encapsulated in the dhcpb6
> request, but directly into the dhcpb6 relay message, because, as the RFC 6939
> specifies, it is added by the Relay server and not by the client itself. I am
> attaching a pcap if someone wants to have a look at it.

> Nevertheless, I will give it a try tomorrow at the lab and I'll let you know.

> Thanks again

> Antonios

> On 3 February 2015 at 20:45, Espen Tallaksen < espen.tallaksen at gmail.com >
> wrote:

>> Hi

>> At least you will need to extract the dhcp-request from the relayed dhcp-packet
>> as it's kind of encapsulated by the relay-agent. You will find an example
>> below:

>> v6relay(1, (binary-to-ascii(16, 8, ":", option docsis.cm-mac-address)));

>> v6relay(1, something) 1 refers to the first relay-agent in the chain.

>> Obviously, you will neew to replace docsis-things with your stuff. I have never
>> tried dhcp6.client-linklayer-addr though. Hope it will help you out.

>> Best regards

>> Espen Tallaksen

>> On 3 Feb 2015 18:21, "Antonios Atlasis" < antonios.atlasis at gmail.com > wrote:

>>> Hi,

>>> I have setup a DHCPv6 relay which forwards the DHCPv6 request to my ISC DHCPv6
>>> server version 4.3.1 running on Centos 6.6.

>>> The DHCPv6 server leases an address successfully to the client.

>>> I have confirmed by using wireshark that the DHCPv6 Relay includes the Option 79
>>> (Client Link-Layer Address) defined in RFC6939 in its Relay-Forward messages.

>>> I want to log the MAC address of the client by using the
>>> dhcp6.client-linklayer-addr which seems to be implemented in this version of
>>> ISC DHCP (I am saying "it seems" because it is included here:
>>> https://deepthought.isc.org/article/AA-01112/0/Newly-Pre-defined-Options-in-DHCP-4.3.html
>>> but not in the official documentation).

>>> In my dhcpd.conf I have tried several configurations, including the one
>>> described here:
>>> https://www.mail-archive.com/dhcp-users@lists.isc.org/msg00622.html
>>> that is:
>>> if (exists dhcp6.client-linklayer-addr) {
>>>         log(info,"option dhcp6.client-linklayer-addr present");
>>> } else {
>>>        log(info,"option dhcp6.client-linklayer-addr not present");
>>> }
>>> but I also get

>>> dhcpd: option dhcp6.client-linklayer-addr not present
>>> Does anyone know if this option is implemented indeed and if so, what I am
>>> possibly missing? Any suggestions?

>>> Thanks

>>> Antonios

>>> _______________________________________________
>>> dhcp-users mailing list
>>> dhcp-users at lists.isc.org
>>> https://lists.isc.org/mailman/listinfo/dhcp-users

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