Cholzhauer,
Um, I am going to take that as a no we don't statically assign IP addresses and that you meant to say the 2012 Server handles our DHCP requests for the phones.
So, have you tried just plugging in one of the phones at a time on the Procurve 5406s?
1. Take one 5340 and plug it in and see if the problem occurs.
a. No Problem: Unplug the new phone and plug in another one.
b. Phones Drop: Unplug the new phone and see if they come back, try another one of the new phones.
Repeat this process to see if the problem persists with all the new phones on the Procurve 5406s or just one of them. If it is just one of them get the phone replaced. If it happens on all of the phones then we go to step 2. If it happens on zero of the new phones on that switch then try two and then three at a time until it does happen.
2. Take on of the new 5340 phones and plug it into the switch of the phones that are dropping.
a. No problem: Unplug the new phone and plug in another one.
b. Phones Drop: Unplug the new phone and see if they come back, try another one of the new phones.
Repeat this process to see if the problem persists with all the new phones on the switch in the other building or just one of them. If it is just one of them get the phone replaced. If the problem persists on all of the phones then we need to look at other factors.
Another test you could try, if you have a PoE brick is plug in the Auxiliary NIC on the back of the HX-5000; if you have a CS-5000 then this is not an option as there is only one NIC. Then statically assign a known open IP address, subnet mask, and gateway, along with the VLAN ID information on each phone and see if the problem occurs. This will eliminate your physical switch that the 5000 resides on as the problem.
As for adding a PEC or a PS-1 what other issues are you experiencing that your Vendor would suggest those as a solution to your problem?
How many phones do you have on the 5000?
How many voicemail ports do you have?
Are you having issues with the phones not responding to button presses?
Does your Auto Attendants seem to be having issues with callers or users are not able to access it?
Thanks,
TE