How To: Update the Right DNS Zone File

One of the first problems people encounter when they are new to DNS is where to start looking when they need to make a DNS change. Say you want to add a new subdomain for a piece of server software you are trying out, but where exactly do you add that new A record the instructions keep talking about?


Many times the server that is handling your web site also handles its DNS records, but there is no guarantee that this is the case with every domain name. We recommend that any time you make a change to a domain’s DNS you check for a few basic bits of information about the DNS setup first. While these checks can seem repetitious, just keep reminding yourself that the one time you fail to check them and you edit the wrong DNS record you could be wasting hours or even days.

Avoid Losing Time Due to DNS

DNS propagation can cost a lot of time if you fail to double check a domain’s DNS. Changing a DNS record, even a small amount, triggers a change which can take 24 – 48 hours for all the DNS servers around the world to receive. Locally a DNS change can take effect in a very short time, but because DNS is a caching system the caching servers around the world all receive the update separately over time.

If a change is made on the incorrect nameserver you might find yourself waiting a day or more for the change to take effect, when in fact the change will never happen because it was made on the wrong nameserver.

Step 1: Whois the Domain to Verify the Nameserver

The first, and most important, step to avoiding DNS pitfalls is to run a quick Whois check on the domain name whose DNS you wish to update.

If you need assistance running a whois check please see our Knowledge Base article New User Tutorial: Whois.

The whois results tell you what nameservers are responsible for that domain’s DNS zone file.

In the results, find the section labeled Name Servers or something similar (whois results very depending on the registrar that controls the domain). In the following example we will lookup the nameservers for buy.com and then find out what the IP address of the primary nameserver is and also who owns the IP:

We start by running a whois on buy.com (note: The whois results in this example have been simplified for instructional purposes):

$ whois buy.com
===
Domain Name: BUY.COM
Registrar: NETWORK SOLUTIONS, LLC.
Whois Server: whois.networksolutions.com
Referral URL: http://www.networksolutions.com
Name Server: DNS03.SAVVIS.NET
Name Server: NS1.BUY.COM
Status: clientTransferProhibited
Updated Date: 28-jul-2011
Creation Date: 12-nov-1998
Expiration Date: 11-nov-2013
Domain servers in listed order:
NS1.BUY.COM 209.67.181.9
DNS03.SAVVIS.NET 209.1.222.246
===

Note that the nameserver information is listed twice, once near the top as “Name Server” and a second time near the bottom of the results as “Domain servers listed in order.” The “in listed order” section is important because it indicates priority, which for this example means that NS1.BUY.COM is the primary nameserver for buy.com.

Step 2: Ping the Nameserver to Obtain Its IP Address

Now that we have the primary nameserver we want to check the IP address that the nameserver is using.

$ ping NS1.BUY.COM
PING ns1.buy.com (209.67.181.9): 56 data bytes
64 bytes from 209.67.181.9: icmp_seq=0 ttl=118 time=68.968 ms
64 bytes from 209.67.181.9: icmp_seq=1 ttl=118 time=65.800 ms
64 bytes from 209.67.181.9: icmp_seq=2 ttl=118 time=65.799 ms

As you can see in the ping results above the IP address that NS1.BUY.COM is responding from is 209.67.181.9.

At this point, if you were an admin for buy.com, you could verify that the server you were working on also had that IP assignment and be 100% sure that you were working on the correct DNS zone file.

But, what if you discover the IP address for the nameserver is not where you expected it to be, and it is responding from a different or unexpected server? Liquid Web technicians find themselves in this situation when a customer contacts us to ask for a DNS update and we discover that we do not control that domain’s DNS. Quite often this is the case when customers utilize their registrar (such as GoDaddy, Network Solutions, etc.) as DNS providers.

If the DNS is controlled by a server that you can’t update you still want to be able to figure out where to go next (or who to contact for the update), and that is where whois comes back into play!

(Optional) Step 3: Whois the IP Address to Verify Allocation

The Whois command can also be used to find out which hosting provider or ISP “owns” a particular IP address. Simply run the command with an IP instead of a domain name (note: The whois results in this example have been simplified for instructional purposes):

$ whois 209.67.181.9
===
#
Savvis SAVVIS (NET-209-67-0-0-1) 209.67.0.0 - 209.67.255.255
Buy.Com SAVV-S230387-2 (NET-209-67-181-0-1) 209.67.181.0 - 209.67.181.255
American Registry for Internet Numbers NET209 (NET-209-0-0-0-0) 209.0.0.0 - 209.255.255.255
#
===

The output from whois tells us that the IP is part of a block (209.67.0.0 – 209.67.255.255) that belongs to Savvis, which has allocated a portion of that block (209.67.181.0 – 209.67.181.255) to buy.com. In short, the output is confirming that the IP address being used for ns1.buy.com is also owned by buy.com.

An Example from Liquid Web Support

If one of our customers registers a domain name at GoDaddy and signs up for an account with Liquid Web, they have the option of utilizing Liquid Web’s nameservers to handle their DNS. But this customer could have GoDaddy handle their DNS while Liquid Web provides the hosting services only.

If the customer contacts our support team for a DNS change, forgetting that their DNS is at GoDaddy, our technician will run a whois request on the domain name, see that the nameservers are not Liquid Web’s, and inform the customer that they need to contact someone else for the change. If the nameservers do not make it apparent who the customer needs to contact, the technician will ping the nameserver, obtain its IP address, and run a whois on the IP to find out what hosting provider owns it. The technician can then direct the customer to contact the correct provider who will then complete the DNS change.

Remember, no matter how basic this check might seem it will help you avoid hours of lost time waiting for your update to take effect!

===

Liquid Web’s Heroic Support is always available to assist customers with this or any other issue. If you need our assistance please contact us:
Toll Free 1.800.580.4985
International 517.322.0434
support@liquidweb.com
https://manage.liquidweb.com/

Be Sociable, Share!
Here's $75, Launch a New VPS Today. Find out why 30,000 customers have chosen our Best-in-Class Performance & 24x7 Heroic Support.