[Dnsmasq-discuss] Single interface, multiple subnets...

Simon Kelley simon at thekelleys.org.uk
Mon Sep 27 11:39:32 BST 2010


Scott wrote:
> Well, what I'm doing is simply trying to have DHCP IP's for 2 different
> subnets (192.168.1.0/25 and 192.168.1.128/25) served out of a single
> interface.  The machines are on 2 different physical network segments.  The
> 192.168.1.0/25 has a default gateway of 192.168.1.1, the 192.168.1.128/25
> subnet has a default gateway of 192.168.1.129.  Routing is set so that the
> DHCP request will route to the DHCP server.  I turn on server 1 & server 2,
> and though both DHCP ranges are set, and the DHCP Request packets from both
> servers are received by the DHCP server, it only serves out a DHCP address
> for server 2, and for server 1 (the server which is on a different subnet &
> network segment) gives the error I indicated below: "Sep 24 12:45:47 server1
> dnsmasq[2640]: no address range available for DHCP request via eth0".
> 

How are packets routed from the network segment containing server1 to
the DHCP server? If it's a different physical segment  then it will be
in a different broadcast domain and DHCP broadcasts from that segment
won't ever make it to the server. Clearly they are, so there's something
more complex happening, but you're not telling us what. The solution to
this problem is almost certainly to use a DHCP-relay, but exactly how
that should be done depends on the details of your routing.

Cheers,

Simon.



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