[Dnsmasq-discuss] dnsmasq responding to DHCPINFORM only

Simon Kelley simon at thekelleys.org.uk
Wed Aug 18 22:19:00 BST 2010

Nabeel Jafferali wrote:
> Is it possible to have dnsmasq run alongside an existing DHCP server on the
> network, but only respond to DHCP INFORM requests with the appropriate
> option #. Essentially, I want to have my existing DHCP server hand out IPs,
> but when the client device doesn't receive option 66 information, it send a
> DHCP INFORM request, which I want dnsmasq to reply to.
> I tried to set up dnsmasq.conf to listen on the appropriate interface, did
> not set it as authoritative, did not include any IP address range, but did
> specify dhcp-mac and dhcp-option entries.

If you enable dnsmasq with a dhcp-range that looks something like


then it will not hand out leases, but it will reply to DHCPINFORM.

BUT, most clients, once they have a DHCP lease, will unicast DHCPINFORM
requests directly to the DHCP server which supplied the lease, so in
those circumstances dnsmasq would never see the request and therefore
not reply.


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