Troubleshoot network issues




I’m sure you’ve come across computers that feel like they have an extra slow Internet connection, and so you start digging through a crazy amount of settings trying to figure out what could be the culprit. In the end you’re left wondering whether your machine is actually the problem, or whether it has something to do with your ISP. Before you run down a rabbit hole I highly recommend giving the web-based Netalyzr tool a whirl.

Netalyzr was put together by the fine folks at the International Computer Science Insitute (affiliated with the University of California at Berkeley). It runs through dozens of tests to check connectivity/reachability, whether your DNS is resolving correctly, proxy usage, and much more. If you’re at your wits end this can provide an excellent starting point for troubleshooting your network issues.

I should point out that Netalyzr does require that you have Java installed and readily available in order to run the tests, and while that would normally be a huge drawback for me the usefulness of Netalyzr offsets some of my hate for Java. If you’re curious what kinds of tests it performs you can check out this example results page or just glance over this list I put together:

  • Address-based Tests
    • NAT detection
    • Local Network Interfaces
    • DNS-based host information
    • NAT support for Universal Plug and Play (UPnP)
  • Reachability Tests
    • TCP connectivity
    • UDP connectivity
    • Traceroute
    • Path MTU
  • Network Access Link Properties
    • Network latency measurements
    • TCP connection setup latency
    • Network background health measurement
    • Network bandwidth
    • Network buffer measurements
  • HTTP Tests
    • Address-based HTTP proxy detection
    • Content-based HTTP proxy detection
    • HTTP proxy detection via malformed requests
    • Filetype-based filtering
    • HTTP caching behavior
    • JavaScript-based tests
  • DNS Tests
    • Restricted domain DNS lookup
    • Unrestricted domain DNS lookup
    • Direct DNS support
    • Direct EDNS support
    • DNS resolver address
    • DNS resolver properties
    • Direct probing of DNS resolvers
    • DNS glue policy
    • DNS resolver port randomization
    • DNS lookups of popular domains
    • DNS external proxy
    • DNS results wildcarding
    • DNS-level redirection of specific sites
    • Direct probing of DNS roots
  • IPv6 Tests
    • DNS support for IPv6
    • IPv4, IPv6, and your web browser
    • IPv6 connectivity
  • Host Properties
    • System clock accuracy
    • Browser properties
    • Uploaded data

Netalyzr Homepage (Java required)