Linux fails to bring up an interface saying the IP is in use, but it's not...

I have a Linux VM in my lab that's failing to start a network interface becaues it thinks the IP address is already in use.

The MAC address it shows of the host that "has the IP address" is that of my Cisco ASA firewall's interface that connects to a switch--the same switch that the VM's host connects to.

I've rebooted everything and the VM still thinks the ASA has the IP address, despite it not (yes I checked that as well).

I've checked everything I can think of and have hit a brick wall. Any suggestions?

Depending on what Virtualization platform you are using, you can change the MAC address of the Virtual machine so that it doesnt clash with the ASA's MAC address. IP address bindings use the MAC address for reference so since the network is broadcasting out that "IP address is at MAC address 1122.3344.5566" that is a good indication of why the interface is having issues coming up. While rare that you will ever have two devices on the same network segment with the same MAC address its just like having two devices with the same IP address... It will cause hell.

^ That. The VM Host will mimic DHCP for the VMs and hand out MAC addresses from a set range. I have had cases where 2 separate servers were trying to assign from the same range of MAC addresses and caused major problems for the VMs. So first check it's not getting the duplicate mac from the HV host.

Then try changing the IP to something else as another test.

Is HV short for Hypervisor or Hyper-V? I've never known any to act as a DHCP server unless its a Type 2 with the VM running in NAT Mode. You wont have a happy network if 2 devices have the same MAC address. Everyone thinks that when you send information from one computer to another on your local area network that its doing it by the IP address. Its all frames at layer 2 and information goes from one computer to another with a source MAC address and destination MAC Address.

Unless I am mis-reading what you are saying BobSutan, it sounds like you have 2 devices with the same MAC address which is causing 2 devices to have the same IP address? Is that correct?

If its just the same IP address, I suggest doing what Biznatch said and change an IP address to something static outside the DHCP range and that should solve the issue.

Found the issue, the ASA was doing proxy-arp because NAT. No big deal.

Fix action was:

config t
sysopt noproxyarp <interface name>