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I just set up a Debian server in our office. We have a business account with comcast without static IP, so I'm using DynDNS to point a domain at the machine. The problem is that I can't resolve the domain from within the network.

It is my understanding that there is no way around this using the comcast business gateway, so I would need to set up some sort of local DNS (if anyone knows otherwise that would be great).

I have a basic understanding of DNS, and I'm assuming that I need a setup that will resolve the domain to the local IP when a user is on the office network and use the global DNS record otherwise. Am I on the right track? If so, what is the best way to achieve this?

All the clients are running OSX.

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Is it really the case that the domain name is not resolving? Or is it resolving to an address that your router isn't letting you access (your externally visible IP). Is there some URL about this alleged Comcast issue? – Kaz May 1 '12 at 3:48
can you connect (to a service, i.e. www (assuming you're planning to host some sort of server)) to the dynamic IP (should be a public IP address) from within the local network? In general, you shouldn't have to setup a local dns server for external dns resolution with dyndns to work. You'd need to have your dns resolvers on clients point to a dns server (forwarder) of some sort (public ones are, and – bangdang May 1 '12 at 4:29
You are right, Kaz. After fixing an error in my setup I was able to resolve the external IP, but of course couldn't access it from behind the router. – dsluder May 1 '12 at 20:12
up vote 0 down vote accepted

Set up a DNS server for LAN access only and hand it's address out via DHCP. That DNS server acts as an authoritative server for your domain but issues LAN address rather than the public address.

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Thanks for all the responses. This particular response turned out to be the best way for me to proceed so marking it as correct. Thanks John! – dsluder May 1 '12 at 20:10

A good solution is to use a router which handles Dynamic DNS, and integrates it with its DNS caching service.

Example: I have a Linksys WRT54GL (got new for about $50) running the Tomato firmware (free). It handles the Dynamic DNS such that my domain resolves to a 192. internal address from within, for all machines on the network.

Furthermore, all of the DHCP names of the internal machines (including printers and such) are served up by DNS properly so they resolve.

I can go either to "webserver" or ""; the effect is the same.

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The Dynamic DNS is pointing to your external Comcast IP which your internal machine cannot access. If you can assign values your routers DNS server make the Dynamic DNS domain name point to your servers internal IP address.

External DNS points to ISP IP address: 71.XX.XX.XX

Internal DNS points to your server's local IP address (local (192.x.x.x or 172.x.x.x or 10.x.x.x), but not loopback ( 192.XXX.XXX.XXX
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