Subnet Mask Change.

[poorsapper]

Little background on the sitution. We have a 2k3 AD domain with some XP, 2k, and 98 machines that connect to the server. We are using a 10.0.84.0/22 network. We have came to a point where we need to change the subnet mask to /21. The subnet mask was changed on the server and shortly after that the 98 machines would not connect to the netowork and we lost printing to not all? but some of the computers. So here is my question is there anything that needs to be changed along with makeing a subnet change. Or is this possible to even change the subnet mask and have a smooth change. Thanks for all the advice and help

Jim

 

[ADB100]

If you are changing a subnet mask to a /21 you are looking at potentially 2046 hosts; so I assume at least 2000 in the same broadcast domain........

If I were you I would re-think your strategy and maybe break the network down into smaller subnets. There are no hard and fast rules for the number of hosts per subnet but generally I recommend a /23 for IP only networks or /24 if any other protocols are in use (IPX etc). Depending on the LAN infrastructure I would normally subnet this down further - usually a single subnet per access switch i.e. a 24-port switch I would use a /27 subnet (2 /27 VLAN's/Subnet's if I were deploying voice as well).
This way the network is more manageable scalable, with Layer-3 switches there is no longer any performance penalty for subnetting your network down, plus using a layer-3 routing protocol for redundancy instead of STP you can have a very fast failure recovery time.

Andy