Dynamic DNS

If you have a server attached to a business-class network, the server probably has a static IP address. This means that the network address the server uses does not change from one day to the next. You can easily create Custom DNS records pointing to static IP addresses and they do not require using Dynamic DNS.

However, computers connecting to the Internet through residential Internet service (home fiber, cable modem, DSL, or dial-up) can have dynamic IP addresses. When you connect, the provider assigns an IP address. It may be an address you have used before, or it may be a new IP address. Depending on your Internet service provider, the IP address could change after weeks, days, or even hours.

Dynamic DNS updates DNS records on our name servers within minutes of a change to your IP address. It works by running a simple client on your computer, which connects to us frequently. When we detect that your IP address has changed, we update your DNS records to match.

For a practical example, let’s say you want to access your home computer while you are at work. You set up pair Domains Dynamic DNS. With Dynamic DNS, you can create a host name like yourserver.example.com. This host name will allow you to find your home server even if your IP address changes.

Using Dynamic DNS

To use Dynamic DNS, you need to be using our name servers. Any domain registered with us can use our name servers and Dynamic DNS at no extra cost.

If you are not already using our Custom DNS, please follow these steps to set it up:

  1. Log into the Domain Name Management System
  2. Click the domain to update
  3. Click Domain Address Settings
  4. Read the warning, read it, agree to the terms of service, and click Enable
  5. Add any records that won’t be updated with Dynamic DNS

Next, you can turn on Dynamic DNS:

  1. Log into the Domain Name Management System
  2. Select Preferences from the drop-down navigation menu
  3. Click Dynamic DNS
  4. Read and agree to the pair Domains Terms of Service and the pair Domains Dynamic DNS Terms of Service.
  5. Click Enable Dynamic DNS
  6. You will be given a pair Domains Dynamic DNS Key. You will need this later. It is a good idea to copy it and save it somewhere, but you can come back to this screen to get the key again later.

Finally, you will need to set up a client on your computer to contact us when your IP address changes. We provide a Web client:

  1. Go to: https://dynamicdns.pairdomains.com/
  2. Enter your pair Domains Dynamic DNS Key and the hostname you want to update. If you want to update dynamic.example.com, you would enter it here, and click Continue
    *Important* If you previously had a record set up in your pair Domains Custom DNS for dynamic.example.com, it will now be over-written, and the old information will be lost.
  3. Read the next page, agree to the Terms of Service, and click Enable Dynamic DNS
  4. Minimize your browser window and leave it running. As long as the window is open, your DNS will continue to update.

Other Dynamic DNS Clients

You can use other Dynamic DNS clients that support the dyndns2 protocol. When you set up your client, you can enter this information:

Username: pairdomains
Password: dynamic_dns_key
Alias or Host Name: the domain or sub-domain that you want to update
Dynamic DNS Server Name: dynamic.pairdomains.com
Dynamic DNS Server URL: /nic/update?
IP Server Name: myip.pairdomains.com /

The IP Server Name field might need to be entered as “Other Information” or “Other Settings” using this format: ip_server_name myip.pairdomains.com /

Please note: connections should be limited to every 5 minutes (300 seconds).

Direct URL

If you want to call a URL directly, this format will work:



ddclient is a Perl based dynamic DNS client available from SourceForge. To run ddclient, you should create a configuration file named ddclient.conf. It should contain this information:

daemon=300 # check every 300 seconds

syslog=yes # log update msgs to syslog





web-skip=’IP Address:’






Before running it, make sure that there is a /var/cache directory on your computer. If you do not have one already, you can make one. Then this command can be used to run ddclient:

sudo /full/path/to/ddclient -daemon=0 -file /full/path/to/ddclient.conf

If you run into problems with ddclient, please run this command and send us the full output:

sudo /full/path/to/ddclient -debug -verbose -noquiet -daemon=0 -file /full/path/to/ddclient.conf

Router Software

DD-WRT software can be run directly on some routers. These settings should work:

DDNS Service: Custom DYNDNS
Server: dynamic.pairdomains.com
User Name: pairdomains
Password: dynamic_dns_key
Hostname: hostname_to_update
URL: /nic/update?
Additional DDNS Options: –ip_server_name myip.pairdomains.com /
Do not use external check:
No Force update interval:10

pfSense is an open source firewall/router computer software distribution based on FreeBSD. These settings should work:

Service Type: Custom
Username: [leave blank]
Password: [leave blank]
Update URL: https://pairdomains:dynamic_dns_key@dynamic.pairdomains.com/nic/update?hostname=hostname_to_update