Why Flush DNS?
The Domain Name System (DNS) works like a phone book for the internet. It maps human-friendly domain names such as "example.com" to numerical IP addresses that computers use to locate each other on the network. Without DNS, you would need to memorize IP addresses for every website you want to visit.
How DNS Caching Works
Your computer caches DNS lookup results locally to speed up browsing. When you visit a website, the resolved IP address is stored in your operating system's DNS resolver cache. The next time you visit the same site, your computer checks the local cache first instead of querying a remote DNS server, which makes the connection faster.
When the Cache Becomes Outdated
Sometimes the DNS cache becomes outdated, containing stale entries that no longer reflect the current state of the internet. This can happen when a website moves to a new server, when a hosting provider changes IP addresses, or when DNS records are updated for any reason.
Problems Caused by Stale DNS Cache
- Inability to reach websites: If a site has moved to a new IP address and your cache still holds the old one, your browser will try to connect to a server that may no longer exist.
- Being directed to wrong or old servers: You might end up on an outdated version of a website or a completely different site altogether.
- Security concerns: If your DNS cache has been poisoned by malicious software, you could be redirected to phishing sites or other harmful destinations without knowing it.
What Flushing DNS Does
Flushing DNS clears the local resolver cache entirely, removing all stored DNS entries. This forces your computer to perform fresh DNS queries for every domain you visit, retrieving the most current IP address information directly from the DNS servers.
Common Scenarios Where Flushing DNS Helps
- Website migration: When a website has moved to a new hosting provider or server and you cannot access it.
- DNS propagation issues: After DNS records have been updated but your computer still resolves to the old address.
- Malware cleanup: After removing malware that may have tampered with your DNS settings or poisoned your cache.
- Troubleshooting connectivity: When you can access some sites but not others, or when sites load intermittently.