[Dnsmasq-discuss] Mutliple Subnets - Different Servers - Chaining

Brad Morgan b-morgan at concentric.net
Sun Jul 11 16:59:46 BST 2010


> I have a fairly simple home network, to which I have recently added a
second subnet to for my virtual 
> machines. While my primary DNS/DHCP server is a Dnsmasq instance running
on my DD-WRT router, my second 
> subnet is hosted from a machine inside the Lan. On that machine I run
multiple virtual machines, and desire > to serve DHCP and DNS information to
them from a second Dnsmasq instance running on the first virtual 
> machine. However I've managed to confuse myself greatly on this subject
going through the Dnsmasq archives.

I also have a collection of virtual machines that I use for testing purposes
at home. I'm using VMware Workstation. For the majority of virtual machines,
I choose NOT to have a second DHCP server but instead configure the virtual
machines to bridge (i.e. share) the virtual host's network adapter. These
machines will get their addresses from my home firewall which is running
dnsmasq.

For a minority of my virtual machines, I have a virtual firewall configured
with two virtual network adapters one of which is configured as above and
the other is configured with a virtual switch to which I can connect other
virtual machines. In this case, the firewall provides DHCP to the sub-net
defined for the virtual switch.

Your configuration is similar to this and I think your problem may be that
the gateway machine isn't forwarding packets correctly, i.e. it isn't
routing properly. Your 192.168.2.0/24 network should only need one DNS entry
and one default gateway (and one DHCP server).

To keep things simple, if you want all the machines in the same domain, then
configure them all in the same subnet. If you want to isolate the virtual
machines, then isolate them completely, i.e. a different domain. 

While it is possible to span a domain over multiple subnets, the DNS
configuration is more complicated. I emulate this configuration (a typical
multi-office network) by using multiple virtual firewalls connected to each
other with virtual VPN circuits. Each "office" will have a separate virtual
switch. VMware handles this configuration very well as the Workstation
product comes with eight virtual switches.

You didn't mention what virtual machine software you are running, but it may
be useful for us to know that to provide further assistance. Also include
the host operating systems as well so we can provide more useful examples if
necessary.

Regards,

Brad 




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