What is DNS?
Domain Name Servers (DNS) are the Internet's equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses.
This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses.
Information from all the domain name servers across the Internet are gathered together and housed at the Central Registry. Host companies and Internet Service Providers interact with the Central Registry on a regular schedule to get updated DNS information.
When you type in a web address, e.g., www.CollegePlannerPro.com, your Internet Service Provider views the DNS associated with the domain name, translates it into a machine friendly IP address (for example woule look something like - 220.127.116.11) and directs your Internet connection to the correct website.
What is a DNS Cache?
A DNS cache is a temporary database, maintained by a computer's operating system, that contains records of all the recent visits and attempted visits to websites and other internet domains.
In other words, a DNS cache is just a memory of recent DNS lookups that your computer can quickly refer to when it's trying to figure out how to load a website. Kind of like the "recently called" list on your cell phone. Rather than looking up a value in the phonebook analogy brought up in the previous section, to speed things up, your computer looks at its DNS cache database (recently called list) for the relevant address to point your browser to.
The potential issue that can arise is if the website has an updated IP address (phone number for analogy purposes) but instead of referring to the DNS directory, your computer relies on its cached value and thus sends you to the wrong/old IP address (calls the wrong phone number).
Troubleshooting DNS Cache Issues
Generally a DNS issue will correct itself in time once the DNS cache expires and your browser attempts a fresh connection to the data center where the CollegePlannerPro service lives.
There are a few things you can try to troubleshoot/potentially solve the issue, but they may be hit or miss.
- Try a different web browser - If the issues are resolved with a different browser, uninstalling and then reinstalling your preferred browser will likely fix the problem.
- Power cycle your modem and router - This will clear your router's cache and thus may resolve DNS errors. To do so:
- Unplug your modem's power cable as well as your router's power cable.
- Allow both your modem and your router to sit for at least 30 seconds.
- Reconnect your modem and wait for it to come back online.
- Reconnect your router to your modem and wait for it to come back online.
- Flushing the DNS Cache (ADVANCED)
Beyond the local caching that is done on your computer, Internet Service Providers could be the cause of issues you are encountering. Many Internet Service Providers frequently check for updated DNS information, but others may only check for new information every 12 to 24 hours and only rely on cached IP addresses based on the last time they checked for new information. This leads us to DNS Propagation.
What is DNS Propagation?
When an IP address for a website is updated, it may take from 24 to 72 hours for or the change to take effect. This period is called DNS propagation.
In other words, it is a period of time ISP (Internet service provider) stations across the world take to update their caches with the new DNS information.
Due to DNS caches of different levels, some visitors might still be directed an old server for some time, whereas others can see the website from the new server shortly after the change.
Generally this issue is corrected for all users after 72 hours from an update in servers/IP address updates.