[Dnsmasq-discuss] dhcp-option=121 doesn't seem to work

[Guennadi Liakhovetski]

On Wed, 19 Dec 2007, Simon Kelley wrote:

> > dhcp-option=3,<default-gateway>
> > dhcp-option=<client-ip>,121,<target-network>/24,<gateway-ip>
> > 
> > where gateway-ip and client-ip are from the same network. Then I run 
> > wireshark on the client during the dhcp configuration, and see no 121 
> > option set. dnsmasq from Debian-etch (stable) version 2.35-1. Also tried 
> > without the <client-ip> - the same. Am I doing anything wrong?
> 
> Go back to you wireshark dump and look at the DHCP request packet going
> >from the client to dnsmasq. In the options section, look for the "option
> request list". If that doesn't include 121 (I suspect it doesn't) then
> that's why the option 121 information is not being sent.
> 
> Most DHCP clients don't support option 121 without tweaking, but I think
> the Debian dhclient maintainer was working on it, so if your client is
> Debian, moving to the latest client version might help.

Right, that is a good tip, thanks! Indeed, it doesn't. You have to specify 
which options to request in the configuration file. Now, I looked through 
the docs (dhcp-options(5)), and didn't find option 121 - does it have a 
name? I also noticed there is a (deprecated?) option 33 "static-routes", I 
added it to dhclient's configuration, and indeed it gets requested. I also 
added it to dnsmasq.conf like

dhcp-option=<client-ip>,33,<target-network>,<gateway-ip>

(this time without the netmask "/24" as it doesn't seem to be supported by 
33), but the option doesn't get sent.

Do you know which dhcp client should support 121? I'm using dhclient ATM, 
maybe it was dhcpcd that you meant? Or is it only supported in testing / 
experimental Debian branches?

> dhcp-range=x.y.z.1,static
> 
> will enable DHCP on that network, but only for known hosts.

Aha, cool, thanks. And it will not prevent x.y.z.2 from getting a lease?

Thanks
Guennadi
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Guennadi Liakhovetski