The next release of IPAM is coming very soon. One of the behaviors we have modified is how we handle duplicate subnets. Many customers, mainly Managed Service Providers, need to manage address space for customers who may have overlapping subnets. For these customers, duplicate subnets are a must have. Unfortunately, for other customers who are managing their internal space and don’t want duplicate subnets, the current behavior of IPAM can cause issues.

In IPAM 2.0, we change all of that. Now, if you don’t want duplicate subnets, simply click on Settings –> IPAM Settings –> System Settings and make sure “Enable Duplicated Subnets” is not checked. New installs of IPAM will have duplicate subnets disabled by default, upgrades will retain the current setting (duplicate subnets allowed).




Duplicate Subnets


Now, I realize those are probably the most boring screenshots you’ve ever seen in a Product Blog post. The excitement is what happens behind the scenes. When the box is not checked (Duplicate subnets are not allowed), we will not allow you to create a subnet that is a duplicate or overlaps an existing subnet. Also, if you are monitoring multiple DHCP server scopes, IPAM will merge the status from those scopes into one subnet (rather than having different subnets in IPAM for each server’s scope). This example is often seen when you have multiple DHCP servers providing split scope assignments for the same subnet. See this documentation from Microsoft Technet on Optimizing DHCP Availability:

The next question is; I currently have duplicate subnets, how do I merge those duplicate subnets so I can take advantage of this new functionality? The easiest way to clean this up for scopes being monitored by DHCP is to simply delete one of the DHCP servers. When you add it and its scopes back, IPAM will merge this data into the remaining subnet. Be careful though, if you have custom fields or notes on any of these addresses, you will lose them if the subnets are deleted. As always, backup your database before making large changes like this.

If you have active maintenance, the IPAM 2.0 RC should be in your customer portal. If you don’t have IPAM yet, simply go here and download a free evaluation: