is there an easy way to scan multiple class Bs and get a simple report showing what /24s are unused?

slashtwentyfore

N00b Question for sure

my company owns several other companies and all together there are about eleven /16s give or take a few ten thousand IPs here or there. about half of this space predates ARIN and as so is now a sale-able asset so it has been determined by the powers that be that we migrate completly off the Legacy space and also determine how much ARIN space we can clean up and move everything to a few small IPv6 blocks and Lease the remaining space to a hosting company.

now i know this statement is fraught with idiotic assertions so before you flame me for any one of dozens just know i had no hand in this 'plan' i simply need to know the following

is there an easy way to scan multiple class Bs and get a simple report for the Executive types showing what /24s are unused? individual IPs are not as important at this point as knowing which blocks are free - if i have to wade through a half a million+ IP addys i think i an going to have to kill myself =-)

kweise

We've just implemented IPAM within the last month, so there might be an easier way to do what you're looking to do than the following.  However, I think this might get you the information you need.

If you use the Subnet Allocation Wizard, you can define the supernet address as your /16 and set the desired subnet size to /24.  The wizard will parse out all of the /24s that can be created within the /16 space once you click the Refresh button.  Select all the created /24s and click next.  If you leave the defaults on the next screen of the wizard and click the Done button, the wizard will create the /16 supernet and add all of the selected /24s to the supernet.  IPAM will then begin to scan all of the subnets within your supernet.  Once you have added and scanned all eleven class B networks, you can go to the Reports menu on the Home tab and find the IPAM: Current Status reports.  There is a report called IPAM - All Subnets that will display statistics for each subnet in IPAM.  It will show you the IP % usage as well as the number of IPs used by subnet. 

Although this takes a few steps, it should get you what you need.

Hope this helps!