To update the present cluster host proxmox following files need to be updated:
/etc/network/interfaces /etc/hosts /etc/pve/corosync.conf (only on one node necessary)
However, corosync.conf needs special way to edit the file!
Edit corosync.conf
Editing the corosync.conf file is not always very straightforward. There are two on each cluster node, one in /etc/pve/corosync.conf and the other in /etc/corosync/corosync.conf. Editing the one in our cluster file system will propagate the changes to the local one, but not vice versa. The configuration will get updated automatically as soon as the file changes. This means changes which can be integrated in a running corosync will take effect immediately. So you should always make a copy and edit that instead, to avoid triggering some unwanted changes by an in-between safe.
cp /etc/pve/corosync.conf /etc/pve/corosync.conf.new
Then open the config file with your favorite editor, nano and vim.tiny are preinstalled on any Proxmox VE node for example.