Basic Troubleshooting Guide

Uh oh, if you’re looking at this page then you might be experiencing a problem with the computer you’re trying to connect to by using No-IP’s services. We’ll use this article to cover some of the most common errors we see, but as always if you’re having trouble, the first place to look for help is on our support page. From there you can get access to our knowledge base and support ticket system.

No-IP Troubleshooting Checklist

1) Does the IP address match the location you’re trying to reach?
2) Is the DNS server reporting the right IP address?
3) Is your router properly configured for your application?
4) Are your ports blocked?
5) Possible workarounds

First things first…Does your IP address match the one in our DNS database?

Log in to your No-IP account on our website from the host location. Once you’re logged in and have accessed your account, check your current IP address by looking at the upper left-hand corner of the page. You should see text that reads “Logged In As: (your username here)” and “Current IP: (your.ip.address.here).” Now go to the Hosts/Redirects page and click “Manage.” Your current host list should appear and the IP address for the host you’re trying to reach should match the IP address you’re logged in from. If you see a different IP address for your hostname than what you expect, that’s going to prevent you from making a connection to that host. If you’re not yet running our No-IP DUC software to track your IP address, you should install it now.

Is the DNS server returning the right IP address?

If the right IP address is being shown in your account, the next thing to check is if the DNS server is returning the right IP address when being asked for that information. The easiest way to test this is to use the NSLOOKUP command from a terminal window. Open a command line window (terminal on Linux machines, DOS box on Windows computers), and type the following: nslookup (yourhost.yourdomain.com).

In response you should see something that looks similar to this:

Server: isp.dnsserver.com  
Address: 10.1.1.1  

Non-authoritative answer:  
Name: yourhost.yourdomain.com  
Address: 192.168.85.33

The IP address returned should match the one you see in your No-IP account. If the DUC software is running and you don’t see the right IP address being returned by the nslookup command, please see our support page for further help.

Is your router properly configured?

The next common source of trouble can be your router. In order to be able to run a server on your network, you’re going to have to tell your router what to do with incoming connection requests from the internet. Since No-IP’s DNS service resolves your hostname to the IP address assigned to you by your ISP and can not resolve your internal network addresses, you need to configure port forwarding in your router. You’ll need to know what port your application uses, and also the internal network IP address of the machine you’re using to serve that application. Have a look at our Primer on Opening and Forwarding Ports on your Router for more information on this.

Another key component that works hand-in-hand with your router can be a firewall. Firewalls need to be configured to allow inbound connections as well or your attempts to connect from the outside world will be met with failure. Among the more popular firewalls is the one built in to Windows® XP. We have an illustrated guide that covers the Windows firewall product here. Other popular firewall or security software includes Norton Internet Security, Zone Alarm, etc. Consult the documentation for your product for specific information about how to configure them.

Remember too, that opening and forwarding ports on a router and punching holes in a firewall effectively exposes your internal network to the internet. You should only open the ports that are needed to get your applications to work and always make sure your computers have all the latest patches and security updates applied in order to minimize the possibility of someone compromising your network.

Maybe your ISP is blocking the port(s) you are trying to use?

If everything to this point checks out OK, then it’s possible that your ISP is blocking the port(s) needed for your application to function properly. ISPs have many reasons for blocking access to certain ports; they usually perform these actions to enforce their terms of service or to try to minimize the flow of unsolicited email. In their zealous attempts to regulate what happens on their networks though, they can sometimes cause problems for legitimate users.

The simplest way to test if your ports are open and properly configured on your end is to use our tool at www.portchecktool.com. Simply put the port number you want to test, 22 in our example, in the box marked “What Port?”, then push the “Check” button. Our server will attempt a connection directly to your IP address and let you know the results. Anything other than a response like this one

  Success: I can see your service on (your.own.ip.address) on port (22)  Your ISP is not blocking port 22

indicates that something is wrong. A response that says “Connection timed out” usually means that your router isn’t properly set up or that your ISP is blocking the port you’re trying to use. Double-check your port forwarding configuration and repair it if need be. If it looks right and you still can’t connect, try running your service on a different port and try the test again.

A response of “Connection refused” from the www.portchecktool.com site is indicative of a potential firewall problem. You may have your port forwarding setup right, but there’s likely a firewall (hardware or software based) that’s preventing the connection from being made.

What now?

If it turns out that the problem is being caused by an ISP’s port block, you have a few options available. In the case of a web server being denied access on port 80, you can use the Port 80 Redirect feature of our DNS service. The Port 80 Redirect is available as a part of any of our No-IP Plus, No-IP Enhanced, and No-IP Free Managed DNS packages. This allows you to specify a different port for your website to use and is transparent to your users.

If the ISP is blocking port 25, used to run an SMTP mail server, then we have different options depending on whether the block is outbound (can’t SEND mail) or inbound (can’t RECEIVE mail).