Solved: clear arp table

nygenxny123 · ‎03-27-2009

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?

Richard Burts · ‎03-27-2009

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

HTH

Rick

View solution in original post

lamav · ‎03-27-2009

What platform and version of IOS are you running?

Thotsaphon Lueangwattanaphong · ‎03-27-2009

Hi Richard,

When you did a "clear arp-cache" command. Is that host(Existing AD) still alive? Are there any connections to that host? Please follow these steps.

http://www.cisco.com/en/US/docs/ios/ipaddr/configuration/guide/iad_cfg_arp_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1096656

HTH,

Toshi

nygenxny123 · ‎03-27-2009

Cisco IOS Software, C2960 Software (C2960-LANBASE-M), Version 12.2(25)SEE2, REL

ASE SOFTWARE (fc1)

Richard Burts · ‎03-27-2009

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

HTH

Rick

Thotsaphon Lueangwattanaphong · ‎03-27-2009

Rick,

I can't explain in that way.

5P!

Thanks

Toshi

nygenxny123 · ‎03-27-2009

great! thx..

is there a diff in the clear arp

and clear arp cache command?

Richard Burts · ‎03-27-2009

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

HTH

Rick

nygenxny123 · ‎03-27-2009

great thx..

sometimes the obvious answers are the easiest ones :-)