Computer Networks/Arp/View

Arp is a Windows command used to view and modify the Address Resolution Protocol (ARP) cache. These activities will show you how to view the ARP cache.

Note: To complete this activity, you must have an administrative user account or know the username and password of an administrator account you can enter when prompted.

Preparation

To prepare for this activity:

1. Start Windows.
2. Log in if necessary.

Activity 1 - View the ARP Cache

To view the ARP cache:

1. Type arp -a and press Enter.
2. Observe the ARP cache entries.

Activity 2 - Clear the ARP Cache

In order to observe the effects of Media Access Control (MAC) address resolution, start by clearing the ARP cache:

1. Open an elevated/administrator command prompt.
2. Type arp -d and press Enter.

Activity 3 - View the ARP Cache

To view the ARP cache:

1. Type arp -a and press Enter.
2. Observe the ARP cache entries. There should not be any entries in the list. If there are, a background process on your computer has contacted a network host or router since the cache was cleared.

Activity 4 - Ping the Default Gateway

To dynamically add an entry to the ARP cache, ping the default gateway:

1. Use ipconfig to display the default gateway address. Note the Default Gateway displayed.
2. Use ping <default gateway address> to ping the default gateway address.
3. Observe the results. You should see replies indicating success.

Activity 5 - View the ARP Cache

To view the ARP cache:

1. Type arp -a and press Enter.
2. Observe the ARP cache entries. There should be an entry for the default gateway showing its Internet (IP) address and physical (MAC) address. There may be other entries, depending on what background process on your computer has contacted a network host.
3. Close the command prompt to complete this activity.

Readings

• Wikipedia: Address Resolution Protocol (ARP)
• Wikipedia: IP Address
• Wikipedia: Media Access Control (MAC) Address

References

• Microsoft TechNet: Arp