Report for source subnet

Report for source subnet

Hello community,

I'm looking for following report:

I want to see the amount of successful logins per subnet. I can see the client ip and username of all successful logins, so the information is basically ready. 
so for example:
User A - Client IP 192.168.10.10
User B - Client IP  192.168.10.11
User C - Client IP 192.168.11.10
User D - ClientIP 192.168.11.11
User E - CiientIP 192.168.11.12

Thats the data i got. What I want is a report telling me:

192.168.10.0 - Amount 2
192.168.11.0 - Amount 3

Anybody realized something like that?
Thank you and best regards
Chris