Option dhcp6.client-linklayer-addr

[Enno Rey]

Hi,

On Tue, Feb 03, 2015 at 03:41:27PM -0500, perl-list wrote:
> 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? 

we were using a Cisco device running IOS XE which adds option 79 by default nowadays. can provide exact image if needed, but "all current" should do.

best

Enno





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

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