Question : DHCP Lease times and IP Phones

We currently have a relatively small network, 20 servers, 2 DC's. 1 DC is handing out DHCP. We are implementing IP phones. Since we do not have 2 data drops at each location the Workstation will be plugging in to the phones, and the phones plugging in to the network.

So the problem is phones need DHCP and workstations need DHCP. Once the phone attains a DHCP address from our DC it is then flagged as VLAN traffic and gets routed to the IP phone server at which point it gets a DHCP assigned address on a different network. So essentially phones need an address on our network when they first boot up, but then they are transferred to a secondary network.

I wanted to figure a way of handling this without running out of DHCP addresses if the power goes out. Basically i didnt want to have 230 devices looking for an address when only 200 are available in the DHCP scope.

That being said. I could set my lease time very low in the DHCP scope, but I am not sure what the consequences of that would be. Say a lease time of like 5 minutes. I am really wondering how much that will slow down our LAN.

Any recomendations?

Answer : DHCP Lease times and IP Phones

if you are running cisco use the IP HELPER-ADDRESS command to convert all your BROADCAST style DHCP REQUESTS into UNICAST style requests to decrease bandwidth consumption on your network.

Also for FIXED users use 4 days of lease time and prevent using NO LIMITED LEASE time since they cause DB inconsistencies if the DHCP service might crash.