VLAN & IP Range for VOIP system across 3 sites
We are having a VOIP system installed later this year, and I need to prepare by reserving an address range and setting up a VLAN.
We are on 3 seperate sites connected via leased fibre (100mb between sites) with a Watchguard at each site and branch office VPNs connecting them all.
DG - 192.168.1.1
DG - 192.168.5.1
DG - 192.168.10.1
Those address ranges were chosen because there are currently less than 254 devices at each site, but the space in between the ranges is reserved in case we ever need to expand, in which case I would change the subnet mask.
So should I choose a single range for the IP phones across all 3 sites (eg 192.168.15.0/24) or a different range for each site, but distinct from the current range, and keeping the subnet mask the same?