Network Utility is located in the /Application/Utilities folder it’s a package that helps you with the most common network troubleshooting tasks instead of using Command line.
NB: in Mavericks the Utility has now moved, click here to find it.
Network Utility has 8 tabs that should be enough for you to diagnose and fix any problems with your network connection:
Info
Gives you general information about your selected network interface. The Interface drop-down menu shows all the different interfaces you currently have active on your current network location. This depends on your machine but the default ones are:
- ethernet (en0),
- Wi-Fi (en1) and
- Firewire (fw0).
There are lots of useful information, i.e. Hardware Address, IP Address.
Netstat
A really useful tool to network administrators for troubleshooting, but not for the average user. Netstat displays results including routing tables, comprehensive network statistics for protocols and multicast information. If you choose “Display routing table information”, you will see a list of all the computers on the network.
Ping
Tests connectivity and latency, when you “ping” an address, you send a small bit of data which is sent back if the destination is available.
You can ping both, the IP and domain name, if you use the domain name it first resolves it to an ip (this proves that you can connect to your DNS) then it will ping the IP.
Lookup
Lookup allows you to get information about a domain or IP address by querying your DNS Server.
Traceroute
Traceroute traces your route across the networks to your destination, each line represents a hop over a router.
You can use it to troubleshoot your connection by finding out the point where your data stopped.
Whois
Whois gives you information about internet addresses and who has registered it. From the pop down menu you can select the whois server you going to query, whois.internic.net is the default.
Finger
By suppling a user account and node address you can learn more information about that user account, like office location and other data.
Due to security concerns the finger traffic is being blocked by several networks.
Port Scan
The final tab is Port Scan, you use this to scan which ports are open on the destination.
You can also use Port Scan to test your own computer by typing bonjour name (client1.local). You can find this name in the Sharing section of System Preferences.
