[Solved] virNetServerMDNSStart:460 : internal error Failed to create mDNS client: Daemon not running

Fix:

Further investigation found avahi was needed for this to work. The final fix was running

yum -y install avahi
/etc/init.d/messagebus restart
/etc/init.d/avahi-daemon restart
/etc/init.d/libvirtd restart
/sbin/chkconfig messagebus on
/sbin/chkconfig avahi-daemon on

Source: http://quags.net/archives/53