Let's say the following is in the HPEL or SystemOut log when attempting to start your WebSphere network deployment manager (dmgr), node, or application server.

[2/27/22 3:09:07:094 CST] 00000001 HostNameMap   E   HMGR0027W: A duplicate host to IP Address mapping has been detected. 
IP Address 10.5.14.125 has a mapping to host names dmgr.example.com and node.example.com.

This occurs when the serverindex.xml file (e.g. /opt/WebSphere/AppServer/profiles/your_profile/config/cells/your_cell/nodes/your_node/serverindex.xml) has two or more different hostnames that resolve to the same IP address. In this example, both dmgr.example.com and node.example.com resolve to IP address 10.5.14.125. This might be perfectly OK, in a scenario where you have multiple profiles on a single server, using the same IP address.

<endPoint xmi:id="EndPoint_1" host="dmgr.example.com" port="12345"/>
<endPoint xmi:id="EndPoint_2" host="node.example.com" port="67890"/>