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Event type DHCP Lease Filling Up My Event log

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A DHCP client sends DHCP inform datagrams to request more information than the DHCP server sent with the original DHCPOFFER. The client may also request repeat data for a particular application. The DHCP server will send a DHCPACK in response to a DHCP inform. The DHCPACK datagram contains all of the options configured in its DHCP scope. A DHCPACK will show up in the Meraki Event log as a DHCP lease Event type, similar to the output below.

This output shows the DHCP server 10.1.1.1 sending a DHCPACK in response to a DHCP inform sent by the DHCP client named MYCOMPUTER:

Jan 5 14:11:52 MYCOMPUTER DHCP lease AP1 Meraki duration 0, server_ip 10.1.1.1, vlan 0
Jan 5 14:11:52 MYCOMPUTER DHCP lease AP1 Meraki duration 0, server_ip 10.1.1.1, vlan 0
Jan 5 14:11:52 MYCOMPUTER DHCP lease AP1 Meraki duration 0, server_ip 10.1.1.1, vlan 0
Jan 5 14:11:52 MYCOMPUTER DHCP lease AP1 Meraki duration 0, server_ip 10.1.1.1, vlan 0

 

Some applications request additional DHCP options that may not be available in the DHCP scope. When this happens the DHCP client will continue to send DHCP informs. This behavior has been seen on Windows clients including XP, Vista and Windows 7. If you are seeing these event types filling the Meraki Event log, you can attempt to find the application or process running on the DHCP client that is requesting additional DHCP information and disable it.

For Windows based operating systems the DWORD registry value below can be added to disable DHCP informs on the client machines network adapter. Once you add this value, reboot your client machine.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUIDofyournetworkadapter} 

Value Type: DWORD

Value name: UseInform

DWORD Value: 0

Warning: These settings have been tested in a lab environment. Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Meraki cannot guarantee that these problems can be solved. Modify the registry at your own risk.

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Last modified
16:11, 17 Aug 2015

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ID: 1426

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