@PJH said:
Well at least we're semi-sane at my work:
172.16/12
10/8
192.168/16
The entire RFC1918 range? :)
At my work we use 192.168.1.0/24 for the office LAN but that certainly is already running out with a few dozen employees: think PC, IP phone, mobile phone, laptop/tablet that almost everyone has, plus the other office things (dev servers, printers, chromecasts, access points, etc)
The production server cluster network uses a few /24s in 192.168/16 and 10/8 (plus there's a few /24s of public IPs floating around)
or any of the 10/8 subnets that the mobile carriers, in various countries, use that could likewise potentially break connectivity.
My mobile phone cellular IP address was 10.70.112.x. I reconnected and got 10.64.13.x. ADSL systems here used to use IPs in 172.16/12. The PtP IP address on my home broadband is 10.20.21.x (the IP address on my end is a proper public address). My home IP range is 192.168.0/24. I used 10.169.42/24 for a while, when I was part of a wireless mesh network. How could you possibly expect to not have clashes here?
On the mobile phone I have seen an IP address in the 100.64/12 range but that was not my usual network. At least this is what is meant to be used for carrier NAT. I know Optus gave out public IP addresses until mid-2012.