We have more than 254 devices and need more IP addresses so we are planning to move from a Class C subnet to a Class B subnet. We are currently on a flat network. Old IP subnet: 10.0.0.x/24 New IP subnet: 10.0.x.x/16 We plan to keep our current IP addresses at 10.0.0.x, but change to a 16-bit subnet mask. We will then add 10.0.1.x/16 as a second subnet. Is this a good plan? Is there anything else we need to do?

We've come up with another plan. We were told that we could just add another class C subnet and the firewall/switches would learn the routes. New IP subnet: 10.0.1.x/24 This would be easier since we don't have to change anything we currently have. Would that work on a flat network?

hmaa, I'm going to move this thread to a more appropriate forum. This forum is for discussions of IT Management and planning - and not so much on the details of IP subnetting. -KevinKevin Remde US IT Evangelism - Microsoft Corporation http://blogs.technet.com/kevinremde

Hello hmaa, If you add a second /24 subnet you’ll need a router in between (such as RRAS). Depending on your network infrastructure, I think it will be much easier to move to a Class B subnet. If you have any further questions or concerns, please do not hesitate to let me know. Best regards, HarryThis posting is provided "AS IS" with no warranties, and confers no rights.

Hello Kevin, As Harry indicated, you cannot simply add a second segment in a different subnet (based on the subnet mask) on a flat network without adding a router between the two subnets. If you can obtain a router, then you can create another VLAN for the 10.0.1.x/24 network. Without the router, you will need to move the subnet mask to the left. It does not have to move from a /24 to a /16. If you do a /23, it will provide you with 512 available IPs. No matter how you change the subnet mask, it will require reconfiguration of your IP nodes. Most of your systems can be reconfigured via DHCP. You will need to update those IP nodes that are hard-coded. You decision has to include factors such as scalability, network performance, security, costs, etc... How IP Packets are Routed on a Local Area Network http://www.anitkb.com/2010/06/how-ip-packets-are-routed-on-local-area.html Visit: anITKB.com, an IT Knowledge Base.

Hi, I just want to check if the information provided was helpful. If there is any update on this issue, please feel free to let us know. We are looking forward to your reply.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.