Cisco ASA, ESX/vSphere, and Duplicate IP’s
Summary: Windows (2003/2008/R2) and/or Linux VM’s added to a VLAN and continuously report duplicate IP’s and Windows assign themselves APIPA (Private Address). Symptoms: (Windows) 169.254.x.x Address shows up as (Preferred) when running ipconfig /all in command prompt Resetting Adapter pops up Duplicate IP Error. Changing VM Network to a dummy network and vm nic reset, causes issue to go away. Changing VM Network back to problem network clears issue until vm is reset or nic is reset. Resolution: Assuming the Cisco ASA is the cause, you can follow the below steps to rectify the issue: Login to the Security Appliance ASDM Select Device Setup Expand Routing Select Proxy ARP Disable Proxy arp on the related interface (usually associated w/ your VLAN) Other command line method: sysopt noproxyarp <interface name> If Windows is the issue for some reason, you can do this: Start –> Run… –> Regedit Find this key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Serv...