i've been asked to change my subnet mask on our network from a to a (we are using DHCP and are using windowsServer 2012). - this should not be an issue for the number of users, however i'm concerned what issues may occur from the change = will devices and their ability to connect become an issue? how to correct or possibly avoid issue? Another piece of this is - i was asked to reduce our ip range of “ x.x.80.2 to x.x.85.254“ to a range of “ x.x.80.2 to x.x.80.254“ again, this should not be an issue for the number of users and any reserved IP's are already in that range - but i'm wondering what issue could occur and how to correct. Will most issues be resolved from a DNS restart and power cycling of devices to force new ip's to be acquired? (i was also going to minimize the dhcp lease time before i attempt the change and restore it to its normal setting after successful completion ) ... any and all advise is very welcome - this is outside of my scope of expertise. i will also note: the place where i can change the scope (ip range) has a section indicating the subnet mask but its greyed out - does that indicate that the ip range change may update the subnet mask automatically (I can’t find another location to change the subnet mask itself ) ?? so many questions - thank you in advance for all advice provided.

*this was requested by our managed firewall team because we are having an issue creating a vpn tunnel between locations due to mismatched subnet masks that cannot communicate with each other.

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    Your plan seems reasonable. As DHCP lease expires, it should renew to the new range. Once you know all have expired, you can switch the subnet mask. Devices that have an issue would likely not be DHCP (hardcoded IP, etc), which typically would be switches, routers, servers, etc. – topshot Jul 27 '16 at 19:30
  • That was my thought too - thank you so much for the reply it's really appreciated : ) – m.nadeau Jul 27 '16 at 19:33

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