Configuration DHCPv4 vivso according to RFC 3925

Hok Hie Tjioe hhtjioe at
Tue Jul 31 07:32:54 UTC 2012

Hi Tobias, Malte,

I wa also truggeling with that part months ago as you can see form the mailing list.
Anyway I have a working solution for that, at least in our environment.

The following configuration on our ISC DHCP server version 4.2.3-P2 is used, I use the example of Malte here:

option space FOO;
option FOO.sample code 1 = text;

option space vivso code width 4 length width 1;
option vivso.FOO code 50000 = encapsulate FOO;
option vivso.iana code 0 = string;

option op125 code 125 = encapsulate vivso;

And in the pool definition the following statement needs to include to send the DHCP option 125:
option vivso.iana 01:01:01;
option FOO.sample "Some Option Text";

P.S. Why that "vivso.iana" statement? For soem reason the DHCP doesn't send the option 125 without that. There seems to be a known bug.

Hope this helps..



 From: Malte Starostik <lists at>
To: Users of ISC DHCP <dhcp-users at> 
Sent: Thursday, July 26, 2012 1:32 PM
Subject: Re: Configuration DHCPv4 vivso according to RFC 3925
Hi Tobias, hi list,

Am Donnerstag, 26. Juli 2012, 12:59:36 schrieb Tobias Jähnel:
> Hi all,
> I'm using ISC DHCP 4.1-ESV-R4 and want to set up an environment as
> stated in the subject.
> According to the dhcp-options manual page I added the following to my
> dhcpd.conf.
> option space FOO code width 1 length width 1 hash size 3;
> option FOO.sample code 1 = text;
> option vendor.FOO code 50000 = encapsulate FOO;
> option vendor-class.FOO code 50000 = text;
> option FOO.sample "Some Option Text";
> option vendor-class.FOO "Some Vendor Class";

I tried this to get CISCO's autoinstall feature working (software upgrade, not 
just auto configuration). 

> I configured my DHCP Client to send option 124 with (fictous)
> Enterprise number 50000 and also told it to request option 125.

CISCO switches' DHCP client requests option 125 without sending option 124.  I 
tried many variations and what you did resembles one of my approaches.

> Unfortunately the Server does not send option 125 back.
> See attached capture file.

I don't have a capture now unfortunately, but well, there was basically no 
option 125 in any of the server's replies.

> If I add the following line:
> option vendor.FOO 01:04:01:02:03:04;
> the DHCP server actually sends back Option 125 with vendor code 50000
> and the given content. But hardcoding my options in hex is obviously
> not what I intend.

Hey foo is what I resorted to in the end, but that's not exactly what I had 
hoped for.

> I would appreciate it if you could tell me what I'm doing wrong.
> Tobias

Me Too (TM), so TIA for shedding some light on this,
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