A DNS cache is a temporary storage of information about previous DNS (Domain Name System) lookups on a device or operating system.
It stores the IP addresses of websites you’ve visited, mapping domain names (e.g., google.com) to their corresponding IP addresses (e.g., 142.250.190.78). This cache allows your device to quickly resolve domain names to IP addresses without querying a DNS server every time, speeding up web browsing and network access.
Key Points:
• Purpose: Reduces DNS query time, improving performance and reducing network load.
• Location: Maintained by your operating system (e.g., Windows, macOS, Linux) and sometimes by applications like web browsers.
• Content: Stores records like domain names, IP addresses, and time-to-live (TTL) values.
• Why Flush?: Clearing the DNS cache (flushing) resolves issues like outdated or corrupted DNS records, which can cause website access problems or point to incorrect servers.
For example, if a website’s IP address changes, an outdated DNS cache might prevent access until flushed. If you need more details or specific use cases, let me know!
How to flush DNS?
To flush the DNS cache, follow these steps based on your operating system:
Windows:
1. Open Command Prompt as Administrator (search for “cmd,” right-click, select “Run as administrator”).
2. Type ipconfig /flushdns and press Enter.
3. You should see a confirmation: “Successfully flushed the DNS Resolver Cache.”
macOS:
1. Open Terminal (search for “Terminal” in Spotlight).
2. Run the appropriate command based on your macOS version:
• For macOS 10.15 (Catalina) and later: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
• For macOS 10.12 to 10.14: sudo killall -HUP mDNSResponder
• For older versions (e.g., 10.10): sudo discoveryutil mdnsflushcache
3. Enter your admin password when prompted.
4. No confirmation message appears, but the cache is cleared.
Linux (Ubuntu/Debian-based):
1. Open Terminal.
2. If using systemd-resolved, run: sudo systemd-resolve --flush-caches
3. Verify with: sudo systemd-resolve --statistics (look for cleared cache stats).
4. If using a different DNS service (e.g., BIND), restart it: sudo systemctl restart named.
Note: You may need to clear your browser’s cache separately, as browsers like Chrome maintain their own DNS cache. For Chrome:
1. Go to chrome://net-internals/#dns.
2. Click “Clear host cache.”
If you need steps for a specific device or browser, let me know!