DHCP duplicate addresses

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DHCP duplicate addresses

L1 Bithead

PA-500, PANOS 4.0.5, DHCP set to "auto", lease time all zeros, one IP pool ( .

Recently I noticed that I was getting duplicate IP messages from Windows computers on my network. I found that certain devices were geting the same IP.  I found that when plugging in two devices both got the same IP address.

Has anyone else seen this? It appears that a lease time of zero started behaving like a lease time of zero instead of unlimited. I have another PA-500 configured the same way with no problems.

Setting a lease time fixed my problem, but I'm curious why after more than a year of use the behavior would change, and why my other PA-500 behaves differently.


Palo Alto Networks Guru

Hi RClary,

Did you observe this change of behavior around the time that you upgraded PAN-OS?  If so, what version were you on before 4.0.5?  It looks like you have a pool of 124 IP addresses, do you have the same number of devices?



L1 Bithead

No upgrade, before I noticed the behavior. I was running 4.0.2 since its release date (4/11) and only started seeing the behavior in the past month. I downloaded and installed 4.0.5 with no change.

Normally I have fewer than 20 devices. I used the command line to clear all leases, and tested it with a network consisting of one switch and two devices, both devices got the same address.

Palo Alto Networks Guru

Please open a case with our support team to investigate.




I have a customer which complains the same problem in a 4.0.5 box. An interface dedicated to Wifi guest access.

He complains to have some machine with IP address in conflict and the following error in the PAN system log:

SYSTEM ALERT : medium : ip address is already in use ip x.x.x.x interface ethernet1/3

The lease configured is 4 hours.

Have you fixed that issue or is a bug?

Thank you and regards.

Walter Doria.

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