Middle of network packet sniffer tools [Advice needed]

Hi Guys,

We have a few Sonicwall NSA 3600 firewall which we use to monitor what from IP to IP to see what ports are getting dropped and open ports as needed.

Moving forward, I was wondering what we can do to do this without using the firewalls packet monitor. e.g. something like Wireshark, but in the middle of the network to monitor packets between specific source IP to a specific destination IP. We currently do this by installing Wireshark on the desired source / destination machine and filtering by the source / destination, surely there is a better way to do this though without having to install Wireshark on every server?

Hope this makes sense