[Dnsmasq-discuss] multiple subnets behind DHCP relay

Simon Kelley simon at thekelleys.org.uk
Mon Mar 21 13:50:52 GMT 2011


Takács Balázs wrote:
> Dear all,
> 
> 
> The relay sends all the request from 10.1.0.1 IP address. The default
> subnet for clients is the 10.1.0.0. This works ok. Based on client
> mac address I would like to place some clients in 195.x.x.0/24
> (public ip)subnet. I have set both the pools for 10.1.0.0 and
> 195.x.x.0 subnets in dnsmasq.conf and placed mac address ip address
> pairs to /etc/ethers file for clients have to get public address. But
> the specified clients still get ip from 10.1.0.0 pool. Is there a
> possibility to force dnsmasq to ignore the DHCP relay address and try
> to give out address even in case of subnet missmatch?
> 

There's no easy answer to this. If you were not using a DHCP relay, it
would work fine: dnsmasq is clever enough to work out all the addresses
that correspond to a physical network. Sadly, the relay only includes a
single address. It's possible for the relay to include a different
address for subnet selection, using the subnet selector option, but that
still only gives you one address and you need two.

I've thought about adding an equivalent to the ISC "shared-network"
declaration, which is not pretty, but would work.

Simon.





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