Appendix A Network Troubleshooting

In this example, we abridge the tracert results table to show only server IP addresses and not domain names by using the -dparameter. We also use the -hparameter to limit the number of hops to 5 to test local connections only.

C:\>tracert -d -h 5 www.zyxel.com

Tracing route to a1524.g.akamai.net [203.69.113.16] over a maximum of 5 hops:

1

<1 ms

<1 ms

<1 ms

172.23.31.254

2

5

ms

4

ms

4

ms

172.23.6.113

3

5

ms

5

ms

6

ms

172.23.6.253

4

17

ms

16

ms

14

ms

218.160.188.254

5

24

ms

25

ms

24

ms

10.42.232.150

Trace complete.

C:\>

arp

Local network transmission is based on MAC addresses. Data transmission between two networks is based on IP addresses.

Address Resolution Protocol (ARP) is a protocol that converts IP addresses into MAC addresses. Before a computer transmits data to an IP address on the same network, it will check whether the IP address exists in its ARP table. If it does, the computer then sends the data directly to the mapped MAC address. If it does not, the computer broadcasts an ARP request to the network. The host whose MAC address maps to the IP address responds.

When you use ping to check the connection to a computer, no response does not mean the computer is not alive on the network. The destination computer may be configured not to respond to any ping requests. However, you can use the arp -acommand line utility to check the IP addresses and MAC addresses of your neighboring computers or devices.

Syntax: arp -a

Parameters: arp [-dinet_addr] [-sinet_addr eth_addr]

The -dparameter can be use alone to remove all entries from an arp table or in conjunction with an IP address to remove just that IP address (inet_addr). The -

sparameter allows you to add entries based on IP address (inet_addr) and/or MAC address (eth_addr).

There are other parameters but these are the only ones you need to use for now.

 

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P-870HN-51D User’s Guide