Wednesday, March 2, 2011

Use Mac's Network Utility to troubleshoot networks

Prepackaged commands

Quick quiz: name the eight operations the Network Utility performs. Many Mac admins won’t even remember that the utility can perform that many functions, much less the actual operations. The actual network tasks and commands that the utility performs are:
  • Info (customizable by specific network interface)
  • Netstat
  • Ping
  • Lookup
  • Traceroute
  • Whois
  • Finger
  • Port Scan
The Info window returns detailed configuration information for a specific network interface. In addition to listing IP address, hardware (MAC) address, link speed and link status, the Info page also lists transfer statistics. The best part, like all the Network Utility tabs, all information is displayed within an easily read GUI.
The Netstat tab displays results from canned Netstat operations, including routing tables, comprehensive network statistics for protocols, multicast information and socket state status. The Netstat data proves helpful when troubleshooting routing issues and network failures by offering route, destination and socket data.
Ping, which tests connectivity and latency, offers just two options: address and number of pings. Techs simply enter the address (either a numeric IP or friendly web address) to test and specify either an unlimited number of pings or a specific limit.

Lookup simplifies testing DNS resolution. Techs enter a numeric or Web address in the provided field, specify the type of information to look up and click the provided button. The command then runs. Among the lookup options are Internet addresses, canonical names, MX records, name servers, and host names, among others.

Traceroute helps identify failures along a route. By tracing the path packets follow to a destination, enterprise administrators can learn where a breakdown is occurring. I’ve solved maddening routing issues with Traceroute’s assistance. I’ve had clients whose attempts to connect to cloud-based servers in Minnesota from Kentucky failed due to bad handoffs by the ISP in Utah. Copying and forwarding the Traceroute screens are what convinced the ISP’s technical staff that the problem was with their network.

Whois assists administrators in determining the owner of registered Web addresses. Besides returning registrar information, Whois searches also display domain expiration dates, name server settings and related information. Multiple Whois databases can be searched, including those maintained by Internic, Network Solutions ,and APNIC.
Finger enables supplying a user account and node address to learn more information about a user account, such as office location, telephone number, or other data. In the Internet’s early days, seeking and obtaining such information was commonly accepted, but latter-day security concerns typically result in finger traffic being blocked by many networks.
The Port Scan tab allows an enterprise administrator to list a specific IP address or site and perform a scan of open ports. To speed results, administrators can also test ports within specific ranges or just a single port using the supplied checkbox option. Such Port Scans can assist staff in ensuring only appropriate ports are enabled, thereby tightening a network’s security configuration.

Quick work of complex commands

The Mac’s Network Utility makes quick work of common, often complex commands. The addition of an easily read GUI makes the Network Utility, and the information it returns, that much more user friendly. Reached from /Applications/Utilities, the Network tool assists engineers in diagnosing common network problems and obtaining critical information needed to speed repair.

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