DNSMASQ issue with "other computers" on network

Fairly up-to-date FreePBX.

I dropped into one of my sites and found a funny problem. I have the (local) phone server set up as the DHCP server for the network. I’m using the DNSMASQ DHCP server on the PBX to manage the DHCP for the network (more phones than PCs, seemed like a good idea).

So, I did a YUM update over the weekend and the PCs stopped being able to access the Internet. I don’t know if I had changed the server before or if I’d just gotten lucky before, but all of the PCs were getting the PBX as their default gateway instead of the network’s actual default gateway.

I’m going to just assume that DNSMASQ used to use the network’s default gateway as the DHCP Router, but the comments in the current DNSMASQ file say that it actually uses the server’s IP now. This means that DNSMASQ assumes that the DHCP server is the gateway machine.

Rather than modify the dnsmasq config file (which is managed by System Admin) I added the –dhcp-option=3,192.168.x.x option in the dnsmasq.service file, ran the “service updater”, and restarted DNSMASQ.

I’ve submitted a ticket to add the default route option to the DHCP service screen, but this will work as an alternative.

There are, of course, lots of other possible solutions, including starting a DHCP service on another server or using the one that comes with the actual firewall. On this network, I could have stood up ISC DHCP on the CRM server, but I decided to see if I could get DNSMASQ to work. It’s working.

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