NetworkTroubleshooting

Network Troubleshooting

This page contains a list of pages giving information about how to troubleshoot network problems.

For example, it could refer to pages saying "if you see a lot of ARP traffic, you might have machines infected with virus XXX on your network", or "if you are getting slow response for HTTP requests, you should look for this on the network".

Beginner?

New to network troubleshooting? Read the /Overview.

"Mysterious" traffic

• Some networks might have a lot of what Ethereal identifies as "Intel ANS probe" traffic. ANS is Intel's "Advanced Networking Services," which provides load balancing, aggregation, and failover for their line of NICs:

  • http://www.intel.com/support/network/adapter/ans/teaming.htm

  As Gerald Combs notes:

  • I'm pretty sure the probes are used for fault tolerance, and they may be used for load balancing. I don't think they're used for link aggregation as it appears to be an implementation of EtherChannel (which doesn't use probe packets AFAIK).

Virus behavior

• Several viruses send a lot of ARP traffic in an attempt to discover hosts to infect; see the ArpFlooding page.

Other sources of network flooding

• Broken/misconfigured software can also cause network or firewall to bleed; see "NetworkFlooding" page

External links

• 3Com's Network Troubleshooting Overview

  Cisco's Internetwork Troubleshooting Handbook. The Overview section provides a good general problem-solving model.

  MOREnet's Documenting Your Network. Good documentation is a prerequisite for effective troubleshooting.

  The Principles of Troubleshooting at InetDaemon.Com shows how to apply the scientific method to network troubleshooting.

  Intel has a document Using Ethereal to Debug SIP and RTP on Voice over IP (VoIP) Products from Intel.

  There's a How To Debug and Troubleshoot VOIP page on The VOIP Wiki that has a bunch of links to information on debugging VOIP problems.