How to Test Firewall Security

Hi Null Byet,

i'm trying to test various firewalls and how they react to attacks, my main problem is that i have no idea on how to start .

My setup is this

Kali linux -->Firewall -->internet simulator -->firewall-->metasploitable2

dose anyone know something simple to try ? my head normally starts to hurt when i try to use metasploit and that's why i use armitage, yet this is not successful .

any help will be greatly appreciated