I did a little reading on perimeter network security and the same phrase kept coming up, our "main firewall" is XYZ. Does that mean companies will utilise more than one perimeter firewall? If so - why, why would you use more than 1? Is there a danger of the firewall settings conflicting with each other and thus the admin not knowing whats in place? I dont understand why people would need/utilise more than 1 firewall - albeit its not my area of expertese.