Please note this is an updated version of a topic originally posted on the Proxmox Forums which I came across whilst testing Proxmox.
This is a simple way to solve routing or masquerade problems via ZeroTier One and PVE for any networking segment.
Step 1
Install ZeroTier onto your Proxmox VE Server
curl -s https://install.zerotier.com | sudo bash
Step 2
Enable IP Forwarding at kernel level
Edit the /etc/sysctl.conf file with nano/vi/whatever and uncomment the following line:
net.ipv4.ip_forward=1
To apply the changes immediately, run:
sysctl -p
File editing will make sure IP forwarding is enabled automatically on boot.
Step 3
Create a service file in /lib/systemd/system/zerotier-one-masquerade.service with the following contents:
[Unit]
Description=Enable ZeroTier One Routing
After=zerotier-one.service
Wants=zerotier-one.service
[Service]
Type=oneshot
ExecStart=/bin/bash -c 'iptables -t nat -A POSTROUTING ! -o lo -j MASQUERADE'
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
Step 4
Reload systemctl
systemctl daemon-reload
Enable created servicessystemctl enable zerotier-one-masquerade.service
Please note, after reboot this service will automatically start after zerotier-one service.
If you want to test/apply without reboot run
systemctl start zerotier-one-masquerade.service
Remember to configure Firewall Rules upon completion as essentially this is an open router that is being configured, this is essential for any servers exposed to internet.