Troubleshooting A Remote Connection

Almost all versions of Windows or Unix (including Mac OSX) have a version of ping available from the command line. They also should have either the command traceroute or tracert available. Older version of MacOS can use the WhatRoute utility. These are some very useful and basic tools for diagnosing network problems and the steps below should be followed when connection problems arise. This is not a comprehensive guide to networking in general, this is just to give you an idea of what to look for when problems occur and help give us useful information when reporting trouble.

Ping Tests

Ping sends a simple packet to a remote host and then waits for a response from that host. Any network host can be pinged, but some firewalls block ping packets and this may result in the host appearing to be down when the service you are interested in is, in fact, available. That said, if you're having connectivitity problems, try the following sequence of ping commands:

```
ping 127.0.0.1
```
If this fails there is a basic problem with the local networking stack. It could either be a configuration problem or (especially on Windows) corruption in the network libraries themselves. Double check all connection settings and if correct try to reboot. If the problem persists, call a support specialist.
```
ping xxx.xxx.xxx.xxx
```
Here the x's represent your own IP address. Failure of this test indicates the same potential set of problems outlined above, and the same solutions attempted.
```
ping 147.155.1.1
```
This will attempt to ping our nameserver without doing a DNS lookup; this should always succeed if general internet access is available. If this fails the fault could be either with the local configuration, the local network, or any network path between your machine and the nameserver. Double check your configuration and see the traceroute instructions below to gather more information.
```
ping www.ameslab.gov
```
This final test will attempt to do a DNS lookup of the hostname and then ping that address. Any hostname can be used, but choose one that should always be available. If this ping fails the problem could be with the DNS server configuration on the local machine, or with the DNS server you're using. Try pinging the DNS server you're trying to use, or try a different server. Also see the traceroute instructions below.

Traceroute Tests

Depending on the operating system being used the command will either be traceroute or tracert. This command can reveal where along the network path problems are occurring. If you are having trouble reaching a particular host or group of hosts, try running traceroute and see where communication is lost (*'s will be reported instead of numbers). Note however, that traceroute packets can also be blocked by a firewall which can cause an available network path to appear down.