We have a
XTM21 where I work. The Watchguard boxes are appliances (Linux boxes) that provide a firewall, QoS, and all that. Ours works pretty well, the UI is a little sluggish, but it does the job well enough.
For your setup you're going to have to setup 2 networks. One with the first tenants, and the 2nd with your customers. You can read more about the products here:
The ISP is going to be giving you a block of IP addresses. For example, the ISP might give you
188.8.131.52/28 as your IP block. This allots you
16 IPs. One for the network (
.48) one for the default route (most likely
.49) and broadcast IP address for the network (
.63) and actual IPs to use (
.62) for actual devices.
Use this CIDR calculator to determine the network topology:
So out of the back of the ISPs modem you've probably got 3-4 ethernet ports. Plug 2 wires into the back of that and those 2 wires go into ports on the Watchguard box. Then you'll need to configure each of those ports for a specific IP from the ISP. They should be perhaps
Using 2 additional ethernet ports on the Watchguard box setup 2 separate class C networks say
192.168.1.0/24. One for the first tenant and the other for your customer.
You'll need to make sure that the 2 networks have firewall rules disallowing each others subnets from being routable to each other as well.
Comment if you need more info, this should get you started.