Existing Phone Server/Asterisk On Same Network

I am having difficulties testing my Asterisk setup because Asterisk feature codes are being treated as phone commands for an existing phone server on the same network. What are some ways that I might be able to get around this? Currently, I can think to setup a VLAN, or simply use a generic hub so that tests phones are connected together, but there is no direct connection to the network.

I will try to configure a simple vlan for the asterisk server as well as the voip phones that will be used. I will post the results at a later date.