clear arp table

Answered Question
Mar 27th, 2009
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we are switching over new server Domain Controller cards


What is the best way to clear the arp table?




I do a show ip arp..and a table of

IP's and macs.


I issue a clear arp command..but the

table reamins


I issue a clear-arp cache command..but the table remains?



Also what about the clear ip arp command?

Correct Answer by Richard Burts about 8 years 1 month ago

Richard


I checked on a router and there is a single command clear arp-cache. So you can execute clear arp and it works (because arp is an abreviation of arp-cache) and of course you can do clear arp-cache. When I try to put a space inbetween arp and cache clear arp cache I get an error for invalid syntax.


HTH


Rick

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lamav Fri, 03/27/2009 - 08:36
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What platform and version of IOS are you running?

nygenxny123 Fri, 03/27/2009 - 08:51
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Cisco IOS Software, C2960 Software (C2960-LANBASE-M), Version 12.2(25)SEE2, REL

ASE SOFTWARE (fc1)

Copyright (c) 1986-2006 by Cisco Systems, Inc.

Richard Burts Fri, 03/27/2009 - 10:02
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Richard


It can be a bit confusing about clear arp because as you state in your original post it appears that the arp table is still there. But if you look carefully you will see that this is not really the case. When you issue the clear arp command the Cisco will purge the entries in its arp table and it will immediately issue arp requests for every address that was in the table. Assuming that the same devices are still alive on the network then they will all respond and a table will be built that looks like the original table. But if some device has powered down then its entry will disappear from the arp table. And if a device has a different NIC then its IP will still be in the table but it will have a different MAC (if you look carefully you can see these differences, but to casual observation the table looks just the same).


HTH


Rick

thotsaphon Fri, 03/27/2009 - 11:22
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Rick,

I can't explain in that way.


5P!

Thanks

Toshi

nygenxny123 Fri, 03/27/2009 - 11:54
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great! thx..


is there a diff in the clear arp

and clear arp cache command?

Correct Answer
Richard Burts Fri, 03/27/2009 - 11:59
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Richard


I checked on a router and there is a single command clear arp-cache. So you can execute clear arp and it works (because arp is an abreviation of arp-cache) and of course you can do clear arp-cache. When I try to put a space inbetween arp and cache clear arp cache I get an error for invalid syntax.


HTH


Rick

nygenxny123 Fri, 03/27/2009 - 12:38
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great thx..


sometimes the obvious answers are the easiest ones :-)

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