XeroBank's representative asked me if it was possible to get a synthetic IP when a remote DNS server doesn't respond. Yes, it is.
MaraDNS can be configured to do one of four different things when all remote DNS servers don't respond:
- Have MaraDNS, in turn, not respond. This is done by putting handle_noreply=0 in MaraDNS' mararc file
- Send a SERVER FAIL message. This is done by putting handle_noreply=1 in MaraDNS' mararc file.
- Send a bogus "this host does not exist" message. This is done by putting handle_noreply=2 in MaraDNS' mararc file, and not setting notthere_ip
- Send a bogus IP. This is done by putting handle_noreply=2 in MaraDNS' mararc file, and also having something like notthere_ip="10.11.12.13" in the mararc file.