ASA 5505 problem (ARP request collision)

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Jul 31st, 2009
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Hi all,

Has anyone seen anything error message similar to this:

4 Jul 31 2009 20:37:13 405001 Received ARP request collision from on interface inside

This is happening with a specific laptop (Vista) that I bring home from work. An IP address does get assigned to the laptop from the 5505 but the 5505 will not allow Internet traffice, only local.

The 5505 seems to be functioning normally otherwise but this particular problem has been driving me crazy for weeks.

If I reboot the 5505, the problem goes away for a while.

Does anybody have any idea what might be going on here?



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vronp Fri, 07/31/2009 - 13:17
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More information.

This only happens when this particular laptop is hitting a wireless access point here. When I hard wire the laptop, no problems.

Erik Ingeberg Sat, 08/01/2009 - 07:53
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This message means that there is an IP address conflict. Two devices are using the same IP address

There could be a few reasons for this. Either you have another IP device on your LAN (another laptop, a gaming console, IP phone...) that has a static IP configured with

Another less likely reason would be that you have a second DHCP server on your network which has the same IP address.

Take another look at the logs, you should find messages about ARP request collision from for two different MAC addresses. If you look at the MAC address on your laptop (by typing ipconfig /all in a command line), you can identify the MAC address of the other device.

Then you can look at this page to find the manufacturer by MAC address (enter 6 first HEX digits):

vronp Sun, 08/02/2009 - 08:13
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I don't believe this is the case. Any static addresses I have are below

Also, when there is an ip address conflict, a window pops up under Microsoft Windows that indicates such.

Also, in the logs, the MAC address is always the same. There is not more than one MAC address.

I believe there is some Microsoft Vista weirdness that is causing a problem on this network.

tu_amor66 Sun, 08/16/2009 - 14:47
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Try unchecking IPV6 on the network connection of the laptop, and see if the problem persists.


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