The Address Resolution Protocol (or ARP) is a crucial component of IP networking on any operating system. The ARP Cache is a collection of ARP entries (mostly dynamic) that are created when a hostname is resolved to an IP address and then an IP address is resolved to a MAC address. The PC stores the mapped address in the ARP cache, and they stay there until the ARP cache entry timeout expires.
Although it doesn't happen very often, a bad ARP entry can cause connection issues. When this occurs, deleting the problem entry can fix the problem. And if it doesn't, you can flush the whole thing and let Windows rebuild the cache.
During this week's TR Dojo episode, I show you how to view the ARP cahce and delete individual entries from it using the arp command and how to flush it with the netsh command.
Check out the following TechRepublic articles for more arp and netsh command tips:
- Add the ARP Gadget to your troubleshooting toolbox
- Quickly gather MAC addresses in Windows XP with ARP
- Netsh reference file allows for easy access to all commands
- Scripting out DHCP reservations in Windows Server 2008 with Netsh
- Creating port policies in Windows Server 2008 with Netsh
For those who prefer text to video, click the View Transcript link below the video player windows or check out Jack Wallen's article, "Quick Tips: Flush the ARP cache in Windows 7," on which this video is based.
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Bill Detwiler has nothing to disclose. He doesn't hold investments in the technology companies he covers.
Bill Detwiler is Managing Editor of TechRepublic and Tech Pro Research and the host of Cracking Open, CNET and TechRepublic's popular online show. Prior to joining TechRepublic in 2000, Bill was an IT manager, database administrator, and desktop support specialist in the social research and energy industries. He has bachelor's and master's degrees from the University of Louisville, where he has also lectured on computer crime and crime prevention.