[Xymon] stop using dns and /etc/hosts

I have a hosts.cfg entry

1.2.3.4 server1 where 1.2.3.4 is server1's INTERNAL IP address but its conn check is red because xymon is actually trying to ping its external, NATTed, address 5.6.7.8 which it cannot reach. Its because DNS is resolving the IP 5.6.7.8 I can use a local hosts file entry to override that again, but I'd rather have some way fo telling xymon to only use entries in hosts.cfg and ignore native resolution. How might i achieve that? cheers Ian