How do you get DHCP if the servers are connected one to another?
I assume that you have a 3rd interface for connecting to the network and Internet. Install Proxmox on each server individually and connect them after that.
Follow this setup:
https://pve.proxmox.com/wiki/Full_Mesh_Network_for_Ceph_Server
The only change is that I made the bond but the IP was set on the bridge not on the bond.
Code:
auto enp175s0f0
iface enp175s0f0 inet manual
auto enp175s0f1
iface enp175s0f1 inet manual
auto bond0
iface bond0 inet manual
bond-slaves enp175s0f0 enp175s0f1
bond-miimon 100
bond-mode broadcast
auto vmbr2
iface vmbr2 inet static
address 172.31.6.2/29
bridge-ports bond0
bridge-stp off
bridge-fd 0