All on one Vlan? This setup, while simple to manage, is most likely wreaking havoc on several different levels. The first thing I would do, in this case, would be to move the VoIP off into its own Voice vlan, with a good router that has specific support for VoIP vlans. Cisco makes several excellent ones, and this will alleviate quite a bit of traffic on your primary data network. It will also offer a more managable QoS. Second I would guess from the large number of used ports there are at least 50-100 workstations on the network in question, and these can be divided up into thier own Vlans based on location, dept, or whatever. This will give you a more organized setup to the network (but this can be done at a later time as this will most likely cause some downtime during reconfig.) There are additional ways to alleviate traffic and allow routing between the multiple subnets and offer you more control on route, permissions, load-balancing and several other benefits. First and foremost, I would suggest the removal of the VoIP traffic from your primary Vlan and then begin planning the design of the network beyond that point.
