Recently I did a foundation for two nodes which to be added (expand) a working cluster at customer premise.
As usual , customer provided me with IPs required for foundation and I did the foundation and expanded the cluster.
So far there was no issue, the next day customer contacted me and mentioned that the LCM inventory task is stuck for last
24 hours.
I joined with customer and had a look at customer cluster, NCC was showing that a duplicate IP is detected,when connecting to
newly added node, on CVM or host, I faces disconnect from time to time, but there was no drop in ping to the new node.
I discussed the matter with customer and customer mentioned that IPs are dedicated for Nutanix.
during my investigation, I thought I will put the host in maintenance mode and restart the host.
unfortunately since the node was not added to the Cassandra ring properly (forwarding state) now I was not able to remove the node from the maintenance mode neither remove the node from the cluster.

Eventually I end up opening a support ticket with Nutanix and they came to our rescue.
As I mentioned,even support agreed that NCC finding , duplicate IP, needs to be confirmed.
by using arping , we were able to find out the second MAC (by trying it multiple times)

#sudo arping -c 2 -w 3 -I eth0 <IPAddress>

Now customer had to check with his network team and eventually they found out that the IP have been assigned to a node with multi NICs.

Since changing IP for a node is recommended to be done as a stand alone, customer agreed to remove both nodes and change IP for CVM and host on each node.We had to remove nodes forcefully to do that we can use below command:
#ncli host remove-start id= skip-space-check=true force=true

once the node was removed from the cluster , i have manually changed the IP address for both CVM and AHV for the removed nodes.
to change IP address for CVM, edit below file and then reboot the CVM
CVM#vi /etc/sysconfig/network-scripts/ifcfg-eth0once it is done, reboot the CVM

to change IP address for AHV,edit below file
AHV#vi /etc/sysconfig/network-scripts/ifcfg-br0
once the changes are done, save the changes in the file and restart the network service
AHV#systemctl restart network.service

That is all and afterward I did the cluster expansion once again with the node(s).

Ahmad Jamali