Comment 9 for bug 1818060

So the error is coming from the ifup-eth script on the instance, which probably looks something like this:

# cat /etc/sysconfig/network-scripts/ifup-eth
if ! arping -q -c 2 -w 3 -D -I ${REALDEVICE} ${IPADDR} ; then
  echo $"Error, some other host already uses address ${IPADDR}."
  exit 1
fi

That's going to do duplicate address detection on the IP.

My first thought was that somehow the distro was using the wrong 'arping' package, as this is iputils-arping package syntax (not arping package), but I think in that case it would have thrown an error with a usage message that would be obvious to spot.

So that leaves two possibilities:

1) Another system does have that IP configured; We can look at the ports on the subnet in question to figure out if neutron somehow allocated it twice with something like:

$ openstack port list --fixed-ip subnet=$subnet

2) Something in the network is responding for the IP because it's mis-configured. This is a little harder to track down, but something like:

$ ping -c1 $IP
$ arp -an

Then we'd have a MAC to chase down.
Running tcpdump could also be used to see where the response is coming from.

Since I don't know much about BMC is there an easy way to insert that first command to get more info? Maybe even just in a test patch?