Linux – Resolve domain to another domain’s IP on Linux via local DNS

Just for additional reference - don't know if it comes in handy with your setup: We're also running a .local network. On Ubuntu machines I've discovered that the mdns interferes with the setup unless you change /etc/nsswitch.conf:

By default this file contains the line

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4

You need to place the "dns" prior to the [NOTFOUND=return] section.

Took a while to hunt down - The ubuntu community support on launchpad was of great help with this. (See my question there for the nature of the problems we had with the setup prior to changing nsswitch.conf)

The difference between nslookup and your browser / ping test is that nslookup will force a DNS lookup, whereas the other tests will will use the normal name resolution lookup order to resolve names.

This involves looking in the DNS cache, as well as static records in the hosts file. It's possible that your computers have static records for your webserver in the hosts file (Windows: C:\windows\system32\drivers\etc\hosts, Linux: /etc/hosts/ ). If a record is in this file then that record will be used, and a DNS lookup will not be performed.

As Zoredache suggested, it may also be a proxy server - as the proxy server will be performing DNS lookups on your behalf (Which will more than likely resolve the public address). That being said, ICMP is not usually proxied - especially in windows, but it's definitely worth investigating regardless.

If you want to troubleshoot - I suggest checking your hosts file, checking the proxy server settings, and if you're still drawing a blank, then flush your DNS cache (Windows: ipconfig /flushdns Linux: /etc/rc.d/init.d/nscd restart) and then run a program like wireshark or tcpdump to determine if your PC is actually sending a DNS request when you do a ping / browser test.