I have a customer that I am replacing there existing firewalls with 2 NSA 2400s. I set one up with no problem ,it is connected to a new T1 threw X1 port and to the internal network threw X0 port and then into one on the network switches. There are 4 Cisco network switches that are linked together. When I setup the other NSA 2400 and connect it to the network we start to have problems with the network. What happens is every so often you will see the activity light on both firewalls X0 port blink very fast and if you try to ping another IP on the network it times out. Also all the workstations on the network lock up there web activity. If I disconnect any one of the X0 ports it clears up.