This is on Ubuntu 10.04 server, using KVM to run Ubuntu guests. This system has been working for a long time and I have not changed anything (other than applying security updates), but today I found dnsmasq no longer responds to requests. I cannot say how long this has been broken for me because I don't frequently use the NAT'd guests. So it could have started just after the last updates or some other event and I just now found it.

I can connect to port 53 with telnet at 192.168.122.1.

I've flushed ip-tables to be sure it wasn't firewall rules and that is not the problem. dnsmasq is running, virsh reports default network as stared. I can't find ANY information on troubleshooting libvirt dnsmasq except that it won't play well with other instances of dnsmasq, which is not the problem. I cannot even find where log entries might be for this service.

Any ideas on where to look for more information?

edit to add: I added another network and that one works fine. I guess I have a workaround but would still like to figure out how to troubleshoot this problem.