Linuxconf sends the following query to the DNS:
nslookup -q=soa 0.0.127.in-addr.arpa
All properly configured DNS servers should answer this request. It is possible for a working DNS to operate without a reverse mapping for the network 127.0.0. This is a flaw and should be corrected. (Run linuxconf on this machine and configure the DNS with it and Linuxconf will silently fix this.)