I just received our Quantum Spark 1575 appliance and would like to request some insight from you folks. We currently have a UDM Pro SE as our firewall/router which connects directly to our ISP. I want to maintain this appliance for the simplicity it offers for maintaining the Unifi AP wireless devices currently connected to it along with any additional wireless devices such as phones etc. I want to place the CP1575 facing the internet & connect the UDMP as our second firewall / router to maintain the wireless network. I have seen a lot of articles where people get lectured to not use a second firewall and vice-versa and several "security" experts advocating the use of a second firewall. I chose the latter. Enough said....
The physical cable connection has been shown different ways. One method depicts a LAN port to LAN port connection as a dynamic DHCP address issued by the upstream router on the 192.168.1.0 network and a second cable from LAN port to WAN port with a static ip set as 192.168.1.2 for the downstream router with the downstream router also being a DHCP server but for a172.16.1.0 network. The reasoning behind this method was so the UDMP could still get it's firmware updates directly from Ubiquity.
Our LAN is a Windows AD server, 192.168.1.0 network that also serves as a web server to host our ERP & website as well a file server. What is the recommended method for connecting these two appliances together and implementing network changes that will most likely have to occur?