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I'm implmenting VoIP on our network across 30 buildings on a University campus. Would it be best to put all the VoIP phones into a single vlan or splits them in separate vlans for each building? Am using a software based PBX system (Asterisk).

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How many phones? How good network? – TomTom Mar 28 '11 at 11:34
Could potential expand to about 450 phones on a fibre network with a 10Gbps back bone. Running Cisco 6500 core and distribution L3 switches. – Stokie Mike Mar 28 '11 at 16:35
Should not make a difference then. One VLAN should be enough. 450 phoens is not a lot of load SIP wise, and for the RTP traffic it should not be a lot and makes no difference either. – TomTom Mar 28 '11 at 19:08
@TomTom Thanks for your advice. At what quantity of VoIP phone would you suggest separate vlans. And what would be your implementation method? Just for knowledge and reference – Stokie Mike Mar 29 '11 at 15:19
Depends, but possibly 4 digits. Phones are very static, little updates, low traffic. 450 phones possibly does no mean a lot of stuff around. I would definitely route the normal lan, but a sip phone vlan... sounds like very inactive to me. – TomTom Mar 29 '11 at 15:30

This is really more of a 'it depends' thing. Keep in mind that any more configuration you do will add to your management overhead. One advantage of putting them all in a separate subnet/VLAN is that you might be able to do better QoS or anything on them.

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