Appendix A Network Troubleshooting

To check the ARP table on a Windows XP computer:

1Click Start > Programs > Accessories > Command Prompt. The Command Prompt screen appears.

2Type arp -aand press [Enter].

The following examples show the typical output of this command:

C:\>arp -a

 

 

Interface: 172.16.1.28 on Interface 0x1000003

Type

Internet Address

Physical Address

172.16.1.5

00-00-aa-19-07-38

dynamic

172.16.1.25

00-18-f3-f0-aa-34

dynamic

172.16.1.44

00-0e-a6-2c-60-10

dynamic

172.16.1.210

00-19-cb-e9-66-33

dynamic

172.16.1.254

00-04-80-4c-a8-05

dynamic

In this example, the Physical Address indicates the associated MAC address. A Type entry with dynamic means it was dynamically learned through an ARP response. Use the arp -s [inet_addr eth_addr] to manually add an ARP entry if you want your computer to connect to the host with the specified MAC address when you access the specified IP address.

You can additionally check whether the MAC address associated with the IP address that you are looking for is correct. In some circumstances, your ARP table may keep a wrong MAC address until the entry expires. You can then manually update the ARP table.

To update the ARP table:

1Type arp -d [inet_addr] or just use arp -dto remove all entries in the ARP table. For example, type arp -d 172.16.1.5.

2Type ping 172.16.1.5 and press [Enter].

3Next, use the arp -acommand again to check whether the MAC address matches what you expected. If it does not, another computer may be using a duplicate IP address on the network. Change the IP address on either computer to an unused one to fix this problem.

route

The route command line utility allows you to display or adjust your computer’s network table. The routing table on your computer contains the default gateway

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P-870HN-51D User’s Guide