Recommended cabling spec for voip

some versions of power over ethernet use the spare 2 pairs, others send it over the ethernet pairs (lst time i checked, oth were part of the IEEE standard - but that was just before ratification).

so - whether you need 4 pairs connected depends on the Voip PoE version.

last time i priced these i could buy a new stackable switch with PoE at the same price as the power injector.

Also, using a switch with built in PoE simplifies the wiring, and cuts down the rack space needed - both have been an issue for me before.

so if you need to replace the ethernet switches anyway (to allow you to fit the new building while the old kit is still in the old place, or you need new for QoS support) - then check the system costs for the various ways you could do this.

some switches also support QoS based on IP address, even if they are only layer 2 - e.g. Cisco and Nortel stackables. Using IP based QoS means you dont have to separate Voip traffic by VLAN (e.g. a PC softphone may not give you that option)

works fine until you add data traffic and load the hub up......