Knowledge Base

Troubleshooting Website Access Issues During DNS Changes and IP Updates

When a website undergoes server migration, IP address changes, or DNS adjustments, users may encounter temporary access issues. This is often because the site was previously accessible with an old IP address, which may remain cached (stored temporarily) by the user’s Internet Service Provider (ISP) or their own devices. Such caching can result in users seeing the old IP address for a while, even though the site is technically updated to the new address.

How Does DNS Propagation Work?

When DNS settings for a domain are updated, it can take some time for the changes to propagate to all DNS servers worldwide. DNS servers generally refresh and update their IP records at scheduled intervals. Typically, DNS updates take about 2-3 hours; however, full propagation across all networks may take up to 24-48 hours.

Why Is the Old IP Address Still Visible?

ISPs cache IP addresses for sites that users have previously accessed, which helps improve loading times. However, when a DNS change occurs, the ISP may continue to show the old IP address until their cache is refreshed. This delay can be longer for devices using custom DNS settings or corporate networks with internal caching systems. During this period, users may see the site intermittently loading from either the old or new IP address. As a result, accessing the site with "www" may work, but without it may not, or vice versa.

Methods to Clear DNS Cache

Clearing the DNS cache can help you see IP address updates sooner. If you are experiencing access issues or continue to see the old IP after a DNS change, try the following methods to clear your DNS cache:

1. OpenDNS Cache Clearing: OpenDNS users can clear their cache here.
2. Google DNS Cache Clearing: If you are using Google DNS, you can perform a cache clear via Google DNS Cache Clearing.

Clearing DNS Cache on Your Computer

If clearing the cache at the DNS provider level does not resolve the issue, you can try clearing the DNS cache on your local device:

1. On Windows: Open the Start menu, go to "Run," and enter the command ipconfig /flushdns to clear your DNS cache. Close all browser windows and try accessing the site again.
2. On Google Chrome: Enter chrome://net-internals/#dns into Chrome’s address bar and click “Clear host cache” on the page that opens. This will clear Chrome's DNS cache specifically.

Using Google DNS to Access Updated Sites

You may also set your DNS to Google’s public DNS servers (8.8.8.8 and 8.8.4.4) to potentially see updates faster. If you are using Google DNS but still experiencing issues after clearing the cache, try accessing the site from a different browser to confirm.

Conclusion

DNS updates can take up to 24-48 hours for full propagation across all DNS servers. During this time, intermittent site access issues or IP address switching are normal. By clearing your DNS cache through the above methods, you may be able to access the updated site sooner.