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Fun with DNS:

Example 1: How to join the party?
party.com resolves to an externally hosted web site, but fun.party.com needs to be able to reach a different server, this one is local at 10.0.2.50, when it is resolved from within the local DNS.

Example 2: Port of no return:
externalwebsite.com forwards to a webserver within the LAN, 10.0.2.9. However, externalwebsite.com:85 needs to resolve to 10.0.2.10, a server running a web-app-based service. Port 85 is forwarded from the NAT router, so that incoming (extenal) traffic goes to the correct place (10.0.2.10:85), and this works, but when precisely "externalwebsite.com:85" is querried from within the LAN, it does not work, because the DNS already points it to 10.0.2.9 (for example for port 80 web traffic).

Are either of these examples possible, and what other configuration needs to take place, other than with DNS, to meet best practices.

Neither example can be done with the Gui front end of this particular server to the best of my current knowledge. I tried to manually update the BIND configuration files, but can not find examples of what exactly I am looking for online, and when I made the changes I expected to work, nothing happened (plus this needs to not result in breaking the DNS.)

This is on OSX Server (Bind 9.10.3), and I am not sure of the relationship of the files for example in '/Library/Server/named' and the GUI front-end of OSX Server.

I'm assuming that working answers would be useful across lots of other *nix and *BSD systems though.

  • Example 1 is straight forward. Example 2 however I've never seen or had a need to do. It may be possible, I've just never done it. – Tigger Dec 7 '16 at 0:38
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    (1) Terminology might help: this is a configuration known as a split-brain DNS configuration. (2) Do the Web forwarding with HTTP redirects, not DNS! :) – Christopher Dec 7 '16 at 1:17
  • @Christopher thanks for the clarification, I have seen some tips that I might be able to use about split-DNS so I could possibly make some more progress just with that. Thanks also for the HTTP redirect idea/terminology; I hadn't thought of that (well, exactly--had considered using server constants to redirect, perhaps overly complex) for this or any other project, so there are 2 great starts there. Will keep this updated – forgotstackxpassword Dec 7 '16 at 1:22
  • @Tigger example 2 I think is occuring mostly because we only have 1 static ip available, but in general I think ports are solved at a different level e.g. the other comments so far, here. – forgotstackxpassword Dec 7 '16 at 1:22
  • Part 2 was just confirmed solved with an http-redirect! Will repost a specific answer sometime (hopefully also after trying part 1) for additional critique if nobody else beats me to it ;) – forgotstackxpassword Dec 8 '16 at 0:02

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