ARP Cache

The Address Resolution Protocol (ARP) cache is a table that saves mappings between Network Layer (Layer 3) and Data Link Layer (Layer 2) addresses. The Network Layer contains the Internet Protocol (IP) addresses, while the Data Link Layer contains the Media Access Control (MAC) addresses.

Each system employing the ARP protocol uses this cache of recent mappings to minimize the number of ARP requests. The Operating System stores the cache in Random Access Memory (RAM).

Sometimes, the Microsoft Windows ARP cache becomes corrupted and has to be cleared. The first sign that may be noticed is that connections to the Internet will time out and fail.

Viewing the ARP Cache

To take a look at the ARP cache, go to the start menu and click on Run. In the Command line interface, type command: C:\>arp -a

Clearing the ARP Cache

To solve this issue, the ARP cache has to be cleared. This is performed with the command: C:\>netsh interface ip delete arpcache. Then click OK.

If Clearing Fails

There are times when the ARP cache cannot work properly because of a bug in Microsoft Windows. At these instances, a system error message appears. The bug happens when Routing and Remote Services are allowed. These services have almost no use and can be disabled.

To disable Routing and Remote Services:

  1. Click the Start button of the Windows Explorer. Go to the Control Panel.
  2. If it is in Category view, switch to Classic View. Then, click the Administrative Tools link.
  3. Double-click the Computer Management link.
  4. Double-click Services and Applications and give another double-click to Services.
  5. Double-click Routing and Remote Services.
  6. Set the Startup Type to Disabled (options are Manual, Automatic, and Disabled)
  7. Click the Stop button for the Service Status.
  8. Hit the OK button to save the changes.

Then, clear the ARP cache once more. The ARP should be full without any error messages.

How Can the ARP Cache Help?

Whatever IP device is currently being used, it will have an ARP cache. This will be utilized in the troubleshooting of network connectivity. If all things are going smooth for ARP, there will be a dynamic ARP entry, with IP and MAC values. If the ARP entry is not complete, the ARP cache can be cleared, then another communication can be attempted.

Additional Reading on ARP Cache