Port forwards work… except DNS

  • I'm slowly building up an uber-router and I've got 1 port forward to a test Apache web server in the DMZ, and another port forward for SSH to the same Apache server.  They work perfectly.  Then I added a virtual IP (IP Alias) and port forwarded DNS on that IP to my internal DNS server (currently on LAN, not DMZ).  The firewall log shows that connections succeed but the DNS request times out.  If I address it internally, it works fine.  I have Squid and SquidGuard installed & configged, and ever since I've noticed that the Upload test from Speedtest.net always fails.  Is there a connection between that problem and this one?

    Any clues as to why 2/3 port forwards work fine, and the 3rd fails even though the firewall log shows it succeeds?

  • Are you forwarding TCP and UDP or only one of them?

  • Both TCP and UDP.  I've gotten caught by that before.

  • Have you confirmed that you can ping to the outside world with the machine in question? If you're forwarding TCP/UDP and you can query it internally, it sounds like your default gateway might be incorrect.

  • *#%#$$@ I'm stupid.  Yes, this secondary DNS server was temporarily hijacked by me for testing, but I didn't reconfigure its network stack.  That's probably exactly it.  Thanks for handing me a brain.  Mine got lost.

  • Yes, that was definitely the problem.  Thanks again!

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