Why can I ping (and access) some websites but not others?

Understanding Partial Connectivity Issues: Why Can You Ping Some Websites and Not Others?

Encountering inconsistent internet connectivity can be both confusing and frustrating. One common scenario involves being able to ping some websites while others remain inaccessible, despite the ability to resolve their IP addresses. In this article, we’ll explore why such issues occur, focusing on why certain domains respond to ping requests while others do not, and what steps you can take to troubleshoot these problems effectively.

The Scenario: When Some Sites Respond—and Others Don’t

Suppose you notice that, every few weeks, your internet connection behaves unpredictably. Using the Windows Command Prompt, you can successfully ping popular sites such as Google, YouTube, and Reddit. Interestingly, even some less-frequented sites like xkcd.com respond to ping commands. However, attempting to ping other frequently used services—say, Discord or Imgur—fails, despite the command line resolving the domain names to valid IP addresses.

This peculiar situation manifests in two ways:
– You can perform DNS lookups, translating domain names to IP addresses.
– You cannot establish ICMP echo replies (i.e., ping responses) from certain domains.

Furthermore, attempting to use applications like Discord often results in connection failures, even when DNS resolution appears successful.

Common Troubleshooting Steps and Their Limitations

Many users attempt standard network troubleshooting methods such as:
– Changing DNS servers (e.g., switching to Google DNS 8.8.8.8)
– Running ipconfig /release, ipconfig /renew, and ipconfig /flushdns
– Restarting the computer

While these steps can resolve certain issues, they are ineffective in situations where the problem stems from network policies, firewall settings, or server configurations that block ICMP packets.

Why Can You Ping Some Domains but Not Others?

1. ICMP Packet Filtering:
   Most servers and modern websites deliberately block ICMP echo requests (also known as ping) to mitigate potential security threats or reduce unwanted network traffic. This means that even if a server is online and accessible, it might not respond to ping requests, giving the illusion of inaccessibility.

2. Domain Resolution vs. Connectivity:
   Successfully resolving a domain’s IP address does not guarantee that the server allows ICMP traffic or is reachable on all protocols. Many content delivery networks (CDNs) or web hosting providers configure their servers to respond to HTTP/HTTPS requests but not to ICMP packets.

3. Network Firewall and Security Settings: