Chapter 4. Simple Network Troubleshooting

In This Chapter

• Doing Basic Cable and Link Tests

• Testing Your NIC

• How to See MAC Addresses

• Using ping to Test Network Connectivity

• Using telnet to Test Network Connectivity

• Testing Web Sites with the curl and wget Utilities

• The netstat Command

• The Linux iptables Firewall

• Using traceroute to Test Connectivity

• Using MTR to Detect Network Congestion

• Viewing Packet Flows with tcpdump

• Viewing Packet Flows with tethereal

• Basic DNS Troubleshooting

• Using nmap

• Determining the Source of an Attack

• Who Has Used My System?

• Conclusion

You will eventually find yourself trying to fix a network related problem, which usually appears in one of two forms. The first is slow response times from the remote server, and the second is a complete lack of connectivity. These symptoms can be caused by: