Upgrading Proxmox Cluster 2.2 -> 2.3

Hi,

We have a running cluster of 4 proxmox nodes (2.2).
We want to upgrade to 2.3 and the idea was to follow one of the instructions, saying to bring vm down, upgrade, restart.

My question is, once first node is up, will it be able to connect to the other three 2.2 nodes?
Should the version be the same for the cluster to run?

Thanks!