Option 61 (Client ID) in DHCPOFFER

Dima Fadeyev dima at scancom.es
Fri Nov 25 18:48:08 UTC 2011


> Tested and I have same result (even asking the client to claim it).
>
> I think, from my knowledge, that cid (opt 61) is only valuable for 
> dhcp server (why the client asks the server for things it already 
> knows). Do you have specials needs for doing this ?
I'm testing the GPON OLT/ONTs from one asian manufacturer. The 
manufacturer is saying that the ONT (CPE equipment) monitors the 61 
option in dhcpoffers to tell if the dhcpoffer is destinated to this 
particular ont or to some other device.

In other words, the ONT would send a dhcpdiscover with a unique option 
61 and monitor for a dhcpoffer which would have the same value set in 
this option. Once such a dhcpoffer is seen, the ONT would accept the IP 
and other relevant data set in dhcpoffer.

The manufacturer have given me this reference 
http://tools.ietf.org/html/draft-ietf-dhc-client-id-01
saying that in part three it is stated that the client identifier must 
be included in dhcpoffer if it is included in dhcpdiscover by client. 
They've also given me the name of dhcp server they are using (and which 
is inserting the option 61 in dhcpdiscover): N2X (Agilent Test Machine), 
which I've never heard of before.
>
> One possible way could be to send back value via a private option 
> (range 224-254) :
>
> option cid-sent-back code 224 = string;
> option cid-sent-back = option dhcp-client-identifier;
> option dhcp-parameter-request-list 1,3,6,12,15,26,28,42,224;
>
> regards,
> laurent
>
>
> 2011/11/24 Dima Fadeyev <dima at scancom.es <mailto:dima at scancom.es>>
>
>     Thanks for your reply,
>
>     I've included this line into my dhcpd.conf:
>     option dhcp-parameter-request-list 1,3,6,12,15,26,28,42,61;
>
>     As you can see, option 61 is included. However I still can't make
>     dhcp server include the option 61 into dhcpoffer. This is how my
>     dhcpdiscover and dhcpoffer packets look like right now:
>
>     On 11/23/2011 08:21 PM, Laurent PROUFF wrote:
>       TIME: 16:00:11.283846
>         IP: > (00:d0:cb:cf:d0:ab) >  (Broadcast)
>         OP: 1 (BOOTPREQUEST)
>      HTYPE: 1 (Ethernet)
>       HLEN: 6
>       HOPS: 0
>        XID: 64217936
>       SECS: 0
>      FLAGS: 0
>     CIADDR: 0.0.0.0
>     YIADDR: 0.0.0.0
>     SIADDR: 0.0.0.0
>     GIADDR: 0.0.0.0
>     CHADDR: 00:d0:cb:cf:d0:ab:00:00:00:00:00:00:00:00:00:00
>      SNAME: .
>      FNAME: .
>     OPTION:  53 (  1) DHCP message type         1 (DHCPDISCOVER)
>     OPTION:  61 (  7) Client-identifier         01:00:d0:cb:cf:d0:ab
>     OPTION:  60 ( 11) Vendor class identifier   udhcp 1.9.2
>     OPTION:  57 (  2) Maximum DHCP message size 576
>     OPTION:  55 (  8) Parameter Request List      1 (Subnet mask)
>                                                   3 (Routers)
>                                                   6 (DNS server)
>                                                  12 (Host name)
>                                                  15 (Domainname)
>                                                  26 (Interface MTU)
>                                                  28 (Broadcast address)
>                                                  42 (NTP servers)
>
>     ---------------------------------------------------------------------------
>       TIME: 16:00:11.284036
>         IP: > (00:22:4d:38:37:27) >  (00:d0:cb:cf:d0:ab)
>         OP: 2 (BOOTPREPLY)
>      HTYPE: 1 (Ethernet)
>       HLEN: 6
>       HOPS: 0
>        XID: 64217936
>       SECS: 0
>      FLAGS: 0
>     CIADDR: 0.0.0.0
>     YIADDR: 10.0.0.154
>     SIADDR: 0.0.0.0
>     GIADDR: 0.0.0.0
>     CHADDR: 00:d0:cb:cf:d0:ab:00:00:00:00:00:00:00:00:00:00
>      SNAME: .
>      FNAME: .
>     OPTION:  53 (  1) DHCP message type         2 (DHCPOFFER)
>     OPTION:  54 (  4) Server identifier         10.0.0.32
>     OPTION:  51 (  4) IP address leasetime      340600 (3d22h36m40s)
>     OPTION:   1 (  4) Subnet mask               255.255.255.0
>     OPTION:   3 (  4) Routers                   10.0.0.2
>     OPTION:   6 (  8) DNS server                10.0.0.2,8.8.8.8
>     OPTION:  12 (  7) Host name                 foobar2
>     OPTION:  15 ( 11) Domainname example.com <http://example.com>
>     OPTION:  26 (  2) Interface MTU             1500
>     OPTION:  28 (  4) Broadcast address         10.0.0.255
>     OPTION:  42 (  4) NTP servers               10.0.0.32
>
>     Best regards,
>     Dima Fadeyev
>
>>     hello,
>>
>>      maybe it can help.... (from man dhcp-options)
>>
>>     *option dhcp-parameter-request-list* /uint16/ [*,* /uint16/... ]*;*
>>     This option, when sent by the client, specifies which options the
>>     client wishes the server to return. Normally, in the ISC DHCP
>>     client, this is done using the /request/ statement. If this
>>     option is not specified by the client, the DHCP server will
>>     normally return every option that is valid in scope and that fits
>>     into the reply. When this option is specified on the server, the
>>     server returns the specified options. This can be used to force a
>>     client to take options that it hasn't requested, and it can also
>>     be used to tailor the response of the DHCP server for clients
>>     that may need a more limited set of options than those the server
>>     would normally return.
>>
>>     regards,
>>     laurent
>>
>>     2011/11/23 Dima Fadeyev <dima at scancom.es <mailto:dima at scancom.es>>
>>
>>         Hello everyone,
>>
>>         I have a quick question. Is it possible to make ISC dhcpd
>>         server insert the option 61 (client id) in DHCPOFFER, in case
>>         if it is present in DHCPDISCOVER?
>>         The ISC dhcpd version we are using is dhcp-4.1.1
>>         (dhcp-4.1.1-12.P1.el6_0.4.x86_64 CentOS rpm).
>>
>>         Thanks in advance
>>
>>         -- 
>>         Dima Fadeyev
>>
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>>
>>
>>
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>
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-- 
Dima Fadeyev
Departamento de Ingeniería de Scancom S.L.

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