I've recently started the process of upgrading an ElasticSearch cluster from 1.x to 5.0. The cluster is hosted on different Azure VMs.
In upgrading the nodes I've had to make some changes to the ElasticSearch.YML file. Two changes in particular are the need to set the network.bind_host to 0.0.0.0 and network.publish_host to the node's ip.
I find without these changes I can't connect to the VM remotely and Nodes can't find one another.
At a high level can anyone explain what these changes mean and why they are needed? The binding to host 0.0.0.0 in particularly has me more than a little confused. Thanks in advance for any help.