[Dnsmasq-discuss] two dnsmasq servers providing dhcp for one domain

Simon Kelley simon at thekelleys.org.uk
Thu Jul 16 16:17:21 BST 2009

Anand Kameswaran wrote:
> I am maintaining an internal private domain using dnsmasq.  However 
> there are n number of  subnets connected via infrastructure VPN, and up 
> until now I have had dnsmasq only on one subnet and it has been 
> succesfully serving DNS for all subnets.  However I now have a need to 
> add DHCP to those subnets.  Now I have succesfully setup dnsmasq to 
> serve DHCP to the subnet it is on.  However on the other side of the 
> VPN, obviously dhcp requests will not be recieved. 
> I was thinking I could setup a second dnsmasq instance on the other side 
> of the VPN, but then each DNSmasq will only know about the DHCP names 
> for the machines on it's side of the VPN.  I don't think DHCP relay is 
> an option (I could be wrong - but it is for a rather large number of 
> subnets)
> Is there a way to configure the two dnsmasq servers to update and/or 
> querry each other?  All machines on the subnets share the same domain, 
> so my understanding is that if dnsmasq doesn't find hostx.domain.com 
> <http://hostx.domain.com> then it will give up.
> Currently the dnsmasq also do forward lookups for external addresses.

Why do you dismiss DHCP relay? That seems to be the perfect solution in 
this case. Dnsmasq can handle lots of subnets without problem.

You need to have a machine on each subnet which can run the DHCP relay: 
it doesn't have to be the VPN router, though it can be.

http://www.thekelleys.org.uk/dhcp-helper/ or the ISC dhcp relay would do 
the job nicely.

I can't see any other way to achieve what you want easily.



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