Fortigate and a Small Business Network

[Suge]

Hello everyone,

First of all thank you for reading my post, as the title states i'm in a position where I need assistance as my problem is out of my reach.

I have a business network composed of :
3 switches (one of which is PoE)
Fiber optic router
QNAP server for data backup
A server that act as our Primary Domain Controller
CISCO PBX for our VoIP
And other equipments such as DVRs for IP cameras ...

I recently bought a Fortigate 60E series next-gen firewall since we don't have one and it's a necessity when it comes to network security, the configuration has been easy enough.
When I connect my computer directly to the firewall's LAN port while the WAN is connected to a fully working Router, everything seems to work, I have access to the internet and all the web/app filtering + policies seem to work just fine. But when I try to install the firewall on our switch so that everyone goes through it before they access the internet it does not seem to work.
Internal interface : 192.168.1.99
Wan interface : 172.16.0.2 (subnets have to be different)

When connected directly to the firewall I can ping both interfaces without a problem, but it's not the case when I install it on the network.

If you have an idea on the nature of the problem I would very much appreciate your feedback, I feel like i've reached a dead end.

PS : I'm not an expert on networking.

Thank you, and good luck for all of you.

 

[sdifox]

Draw some diagram so it is clearer what you mean?

 

[Suge]

 

[sdifox]

Where is the ONT?

 

[Suge]

sdifox, thank you.

This is the current build, (the previous image is what I want to achieve) :

 

[sdifox]

ONT - Firewall - Main router is standard setup unless you need dmz.

 

[Suge]

Right now, no need for DMZ at all, we work with a main router that uses Optic Fiber, it gives internet access to all the equipments, everything works just fine. I want to install the firewall between the router and the network, but the problem I mentioned persists.

Thank you for understanding sdifox, and i'm sorry I don't understand what you need to get a better idea on what could be the problem.

 

[sdifox]

Right now, no need for DMZ at all, we work with a main router that uses Optic Fiber, it gives internet access to all the equipments, everything works just fine. I want to install the firewall between the router and the network, but the problem I mentioned persists.

Thank you for understanding sdifox, and i'm sorry I don't understand what you need to get a better idea on what could be the problem.

Your ONT box is also your main router? You may need to disable the routing on the ONT, attach firewall to ONT and the have your (newly setup) main router uplink to firewall.

 

[Suge]

Thank you for your answer sdifox, i'll look further into it and if I find out anything more, i'll make sure to up this post with the details.