This seems to be the simplest pattern for getting remote access to your LAN. It doesn’t require access to the LAN’s router or have some of the pitfalls of bridging. This requires a Linux PC or VM, something that runs iptables, on your LAN. A raspberrypi works. This is a NAT/Masquerade setup.
Possible Disadvantages:
No broadcast/multicast across networks (but the mobile OS’s don’t allow this anyways).
Can’t initiate connections from the LAN to an external ZeroTier client.
For Example:
| Info | Example | Shorthand Name Below |
|---|---|---|
| ZeroTier Subnet | 172.27.0.0/16 | ZT_SUBNET |
| ZeroTier Network ID | d5e04297a19bbd70 | ZT_NETWORK_ID |
| Physical Interface Name | eth0 | $PHY_IFACE |
| Physical Subnet | 192.168.100.0/24 | $PHY_SUBNET |
| ZeroTier IP Address of “Router” | 172.27.0.1 | $ZT_ADDR |
| ZeroTier Interface Name | zt7nnig26 | $ZT_IFACE |
sudo zerotier-cli join $NETWORK_ID
sudo zerotier-cli listnetworks
Authorize it at my.zerotier.com/network/$NETWORK_ID
The listnetworks output has the ZeroTier Interface name under
At my.zerotier.com/network/$NETWORK_ID -> Settings -> Managed Routes
This adds another route to every device joined to the ZeroTier network.
| Destination | (Via) |
|---|---|
| $PHY_SUBNET | $ZT_ADDR |
For example:
| Destination | (Via) |
|---|---|
| 192.168.100.0/23 | 172.27.0.1 |
Configure the destination route as slightly larger than the actual physical subnet, here /23 instead of /24 (a smaller number is a bigger subnet in this notation) This makes devices that are on both the physical and the ZeroTier network prefer the physical connection.
This can vary depending on linux distribution. Typically:
Edit /etc/sysctl.conf to uncomment net.ipv4.ip_forward. This enables forwarding at boot.
To enable it now
sudo sysctl -w net.ipv4.ip_forward=1
Assign some shell variables (personalize these)
PHY_IFACE=eth0; ZT_IFACE=zt7nnig26
Add rules to iptables
sudo iptables -t nat -A POSTROUTING -o $PHY_IFACE -j MASQUERADE
sudo iptables -A FORWARD -i $PHY_IFACE -o $ZT_IFACE -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i $ZT_IFACE -o $PHY_IFACE -j ACCEPT
Save iptables rules for next boot
sudo apt install iptables-persistent
sudo bash -c iptables-save > /etc/iptables/rules.v4