Motivation

Use a Raspberry Pi as a bridge into my home LAN. The pi is plugged into a switch, which is plugged into an airport express, which is plugged into a cable modem; Nothing fancy.

This isn't a tutorial. Just some example output from a working setup.

steps

off the top of my head, here's the order I would do it in:

make sure plain old device to device zerotier is working with my LAN/Router/Firewall/ISP
(STOP HERE to troubleshoot first if not^)
connect keyboard and monitor to pi, or get ready break networking and lose ssh to your pi a few times.
know what subnet my physical LAN uses (192.168.82.0/24)
know what my physcial LAN dhcp range is (192.168.82.101 - 192.168.82.200)
create network at my.zerotier.com
set up managed routes and address ipv4 auto-assign; make sure it doesn't overlap with the physical dhcp server range.
install zerotier (on pi)
join pi to zerotier network (on pi)
set allowManaged=0 (on pi ) sudo zerotier-cli set <networkID> allowManaged=0
authorize pi (at my.zerotier.com)
check bridge and do not auto-assign, just on the pi (at my.zerotier.com), in the wrench icon
write out /etc/network/interfaces (on pi, see below)
restart networking
should be working now
join a phone or something and test (over LTE)
power cycle pi and see if it works without any manual intervention

Example

sudo zerotier-cli listnetworks -j

[
 {
  "allowDefault": false,
  "allowGlobal": false,
  "allowManaged": false,
  "assignedAddresses": [],
  "bridge": true,
  "broadcastEnabled": true,
  "dhcp": false,
  "id": "93afae5963d77bcd",
  "mac": "ce:d8:4e:df:da:41",
  "mtu": 2800,
  "name": "nachos deer",
  "netconfRevision": 361,
  "nwid": "93afae5963d77bcd",
  "portDeviceName": "zt0",
  "portError": 0,
  "routes": [
   {
    "flags": 0,
    "metric": 0,
    "target": "192.168.82.0/24",
    "via": null
   }
  ],
  "status": "OK",
  "type": "PRIVATE"
 }
]

cat /etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto eth0
iface eth0 inet manual

auto br0
iface br0 inet static
	address 192.168.82.5
	netmask 255.255.255.0
	gateway 192.168.82.1
	dns-nameservers 127.0.0.1
	bridge_ports eth0 zt0
	bridge_fd 0
	bridge_maxage 0

ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP group default qlen 1000
    link/ether b8:27:eb:2c:c1:8c brd ff:ff:ff:ff:ff:ff
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether b8:27:eb:2c:c1:8c brd ff:ff:ff:ff:ff:ff
    inet 192.168.82.5/24 brd 192.168.82.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 2605:e000:160d:4587:ba27:ebff:fe2c:c18c/64 scope global mngtmpaddr dynamic 
       valid_lft 604583sec preferred_lft 604583sec
    inet6 fe80::ba27:ebff:fe2c:c18c/64 scope link 
       valid_lft forever preferred_lft forever
4: zt0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 2800 qdisc pfifo_fast master br0 state UNKNOWN group default qlen 1000
    link/ether ce:d8:4e:df:da:41 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ccd8:4eff:fedf:da41/64 scope link 
       valid_lft forever preferred_lft forever

brctl show

bridge name	bridge id		STP enabled	interfaces
br0		8000.b827eb2cc18c	no		eth0
							zt0

laduke/zerotier-rpi-bridge.md

Motivation

steps

Example

laduke commented Feb 21, 2020