DynDNS IP issues w/ a bridged wireless network

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_cashel

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I've got a wireless network here in the house that I was able to bridge over to a second smaller house I have nearby. I used this guide HERE @ AnandTech w/ my main router being a DI-624 and the second router a WRT54G flashed with the Alchemy firmware.

Everything works, except I've noticed that one computer hooked up to the main router and my server (running Ubuntu) hooked up to the second router have the same external IP. How can I change this? I think this may be causing my server to be inaccessible via SSH or telnet. What's wierd is that I can ping the DynDNS address assigned to the IP, but I cannot ping the IP itself. I have forwarded the ports on both routers, but that hasn't helped any.
 
_cashel said:
What's wierd is that I can ping the DynDNS address assigned to the IP, but I cannot ping the IP itself. I have forwarded the ports on both routers, but that hasn't helped any.
Click to expand...


You can ping the DynDNS address... DynDNS should return your OUTSIDE Internet facing IPaddress. That'll be available all the time, because it's the primary router. You said you can't ping the "ip itself" is this the local IP of the server behind the router? if so then you have a connectivity issue between routers, I'd guess.
 
Nate7311 said:
You can ping the DynDNS address... DynDNS should return your OUTSIDE Internet facing IPaddress. That'll be available all the time, because it's the primary router. You said you can't ping the "ip itself" is this the local IP of the server behind the router? if so then you have a connectivity issue between routers, I'd guess.
Click to expand...


No, what I meant was that I could ping the address, say test.dyndns.org, and receive a response. When I ping the actual IP, which is external, not local, I get a response time out. This is the same IP detected on the DynDNS site, and it's the same IP attached to the address.
 
If no one is answering, try giving a little more information to help us out. I'm a bit confused by your question. Are you saying that from within your LAN, you can ping the server by DynDNS hostname but not by IP?

It would be really helpful if you could provide a diagram of your network, specifically showing IP addresses for the server and both LAN and WAN sides of your routers so we can get an idea of your configuration (you don't have to give your real external IP).
 
Yes, that's exactly what I'm saying. Sorry about the confusion, but here's the diagram

netdiag1.jpg


The bottom number is the external IP (not the real one), note how they're all the same. Is this what you're looking for? Let me know if you need any more information.
 
Excellent diagram.

You are correct, from the outside world, your external IP will appear the same for all computers on your LAN because you're sharing one DSL connection. So your DynDNS hostname will be that same IP.

However, inside your network, they will all have private IPs, as you describe in your diagram. You have probablly forwarded certain ports on your router to redirect to your server, so people on the outside can access it using your DynDNS name.

The problem comes however when you try to connect to that hostname from within your network, and this usually turns out to be an implementation of the software on your router. I'm not too familiar with the DI-624, but with my DI-604, it doesn't handle traffic the way you would expect.

For instance, if you were to access 12.12.123.123 from inside your network, you might expect the packet to travel to the outer router, then the router realize that it holds that external IP, then route back into your internal network, forwarding the traffic to your server according to your port forwarding rules.

However, many routers aren't that intelligent. Most of them have forwarding rules that are implemented something like IP tables, which state "traffic arriving on my WAN port with destination port xx should be forwarded to internal IP 192.168.0.40." The problem is the traffic you send doesn't arrive on the router's WAN port, it arrives on the LAN port. Thus the previous rule isn't valid, and the traffic winds up getting routed to localhost, which is the router itself. The router may not be running a service on that port, thus the traffic might be denied.

This is a generalization of the problems with using DynDNS hostnames within a lan. You should still be able to ping the external IP address of the router, so it really doesn't explain what you're seeing. But just keep in mind that any pings or other packets going to yourhost.dyndns.org or to your external IP will probably end up at your router rather than the private LAN host that the outside world sees.
 
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