Windows

Flush the ARP cache in Windows from the command line

Bill Detwiler shows you how to clear a specific entry from the ARP cache using the arp command and flush the whole thing with the netsh command.

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:

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.

You can also sign up to receive the latest TR Dojo lessons through one or more of the following methods:

About

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 supp...

12 comments
pakoppan
pakoppan

Hello, Where is the ARP.gadget? I can't see it in the zip file. Thanks

oldbaritone
oldbaritone

Doesn't a cold-boot flush and rebuild the cache? The good-old "have you tried rebooting" is probably the easiest way out. If something has corrupted the ARP cache, there's probably a good chance that something else is corrupt too, and a reboot would be a good idea anyhow.

joseph_mcmanus
joseph_mcmanus

you used to make the transcripts of your videos EASILY available, well they aren't any more, and the "Get transcript" hotlink doesn't work on this video. can you do something about this as I love your videos AND the info in them is invaluable. I have a collection of some of them (but not recently) and I would most certainly like this one for my info file. Tnx, & L8R

rapell
rapell

Sure i have flushed the ARP cache, and also used netsh to reset the tcp/ip stack. Winsock!

Bill Detwiler
Bill Detwiler

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. In 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. Have you ever flush the ARP cache on a Windows machine?

shamusjennings
shamusjennings

You should never have to reboot. If your machine needs to be rebooted, you need to reconsider the software you are using. The days of Windows 9x are over.

Bill Detwiler
Bill Detwiler

When I click the "View Transcript" link below the video player window, the transcript appears in a pop-up as it should. If you're using a script blocker (such as NoScript) or a ad blocker (such as AdBlock), you'll need to allow the following domains: techrepublic.com bnet.com zdnet.com com.com cbsinteractive.com You'll also need to make sure your browser isn't blocking pop-ups from TechRepublic.

pakoppan
pakoppan

Thanks for the reply. I missed the rename part. Sorry. Cheers

boomchuck1
boomchuck1

You're kidding me right? I can't tell you how many problems with applications, MS and others, and OS lockups I've solved with a reboot. This is in XP and 7. And, I'll extend that out to other products such as our BlackBerry phones, iPod from home, and even the TV set!

JCitizen
JCitizen

I've fixed many a problem rebooting Vista/Win7 system units. Networking problems as well. I really think the problem is more today's hardware, which is on the verge of the limits on quantum physics as it is.Especially with dual core quads and CPUs with six processors.

Bob G Beechey
Bob G Beechey

View Transcript does not work in IE9 regardless of compatibility mode setting. I had to view in Chrome. I also had to use Chrome to write this answer - login popup did not work in IE9