Troubleshoot DNS issues

  • Last updated on: 2018-11-05
  • Authored by: Rackspace Support

This article shows you how to resolve issues in which the Domain Name System (DNS) doesn’t appear to be updating properly from Cloud DNS entries. It helps you diagnose if the DNS issue should be remedied from the customer side, or if you should escalate it to Rackspace Support. It also describes information that you should include when you create a ticket to expedite Rackspace’s response.

Check the system status and open support tickets

Check the Rackspace system status page for open issues that might be affecting your Cloud DNS. Also log in to the Cloud Control Panel and check for current support tickets about Cloud DNS to ensure that there isn’t a known problem.

Try a different browser

If the DNS doesn’t appear to be updating and resolving correctly, check the domain in another browser to ensure that the issue occurs across multiple browsers. If the domain resolves properly in another browser, then it’s likely that a cached site on the original browser is using outdated information. Clear the cache of the browser that’s experiencing the problem and check the domain again.

Check the authoritative name servers

If the issue persists on multiple browsers, check the authoritative name servers to ensure that the DNS records are updated to reflect Rackspace’s data.

To check the name servers, open Terminal and run the following command:

dig ns <domain>

The output displays the name servers that are being used at the far right of the window under ANSWER SECTION, as shown in the following image:

The two name servers that should appear for Rackspace Cloud are and

If the name servers are different, verify that they’re set correctly at the registrar where the domain name is hosted.

If the name servers are correctly set as Rackspace’s stabletransit instances, note that it can take up to 48 hours for the name servers to propagate fully. You might need to wait for propagation to occur.

Note: For more information about DNS lookups, see Using dig to query name servers (for Linux® and macOS®) and Check DNS records on Windows with nslookup (for Windows®).

Check the Time to Live

After you confirm that the registrar is correctly pointing the domain to Rackspace, check the Time to Live (TTL) of the domain in Cloud DNS.

The TTL is the amount of time that must pass before the data expires and new data is pushed. For example, if you have a domain set in Cloud DNS and it has a TTL of three days (the default TTL), then even if you update the data in Cloud DNS, it does not update globally until three days have passed, and the data has expired. Therefore, it’s important to check the TTL of a domain in the Cloud DNS.

Use the following steps to change the TTL for a domain:

  1. Log in to the Cloud Control Panel.

  2. In the top navigation bar, click Select a Product > Rackspace Cloud.

  3. Select Networking > Cloud DNS.

  4. Locate the proper DNS record and click the gear icon to the left of it. Then click Edit Time to Live (TTL).

  5. If the TTL is very high and a flush of the DNS is urgently needed, create a ticket with Rackspace Support by clicking Ticket > Create Ticket at the top right of the Rackspace Cloud Control Panel.

  6. Click Create Ticket, select Cloud DNS as the Category, and provide an explanation of the steps that you have already taken.

Check the hosts file

If the DNS issue is specific to a single computer, check the hosts file that’s stored on that machine. The hosts file contains a list of host names and IP addresses that your computer typically checks before it performs a DNS lookup.

The nslookup and dig commands don’t check this list of host names. If the IP address that your application (for example, ping) is using doesn’t match what appears in the response to the lookup request, this mismatch might be causing the DNS issue.

The hosts file is stored in one of the following locations:

  • Linux: /etc/hosts
  • Microsoft® Windows: C:\\Windows\\System32\\drivers\\etc\\hosts

Each line in the hosts file represents one record. A hash sign (#) at the beginning of a line indicates that the line is a comment and is ignored.

If the domain appears in the list with an incorrect IP address and the line isn’t commented out, the incorrect IP address is probably causing the problem. Add a hash sign at the beginning of the line to comment the line out.

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