RFC1918 is a minefield. This is your map.
RFC1918 is an internet standard that designates certain ranges of IPv4 addresses for use in private networks:
- 10.0.0.0/8
- 172.x.0.0/16 (x must be between 16 and 31, inclusive)
- 192.168.x.0/24 (x must be between 0 and 255, inclusive)
All of these address ranges are not routable on the internet. Because they are meant to be used internally on private networks, they can be used freely and without reservation.
Sometimes, users and administrators need to connect from one private network to another using a VPN. This becomes challenging if the two private networks use identical or overlapping subnets.
| Subnet | Start | End | Reason |
|---|---|---|---|
| 10.0.0.0/24 | 10.0.0.0 | 10.0.0.255 | Commonly used |
| 10.1.1.0/24 | 10.1.1.0 | 10.1.1.255 | Commonly used |
| 10.10.1.0/24 | 10.10.1.0 | 10.10.1.255 | Default network (Asus) |
| 10.1.10.0/24 | 10.1.10.0 | 10.1.10.255 | Default network (Comcast) |
| 172.16.0.0/24 | 172.16.0.0 | 172.16.0.255 | Commonly used |
| 172.17.0.0/16 | 172.17.0.0 | 172.17.255.255 | Kubernetes |
| 172.20.10.0/28 | 172.20.10.0 | 172.20.10.15 | Apple iPhone/iPad Personal Hotspots |
| 192.168.0.0/24 | 192.168.0.0 | 192.168.0.255 | Default network (Linksys, Huawei) |
| 192.168.1.0/24 | 192.168.1.0 | 192.168.1.255 | Default network (Linksys, Huawei) |
| 192.168.2.0/24 | 192.168.2.0 | 192.168.2.255 | Default network (Linksys) |
| 192.168.3.0/24 | 192.168.3.0 | 192.168.3.255 | Default network (Linksys, Huawei) |
| 192.168.4.0/24 | 192.168.4.0 | 192.168.4.255 | Default network (Zoom, ZyXEL) |
| 192.168.8.0/24 | 192.168.8.0 | 192.168.8.255 | Default network (Huawei) |
| 192.168.15.0/24 | 192.168.15.0 | 192.168.15.255 | Default network (Linksys) |
| 192.168.16.0/24 | 192.168.16.0 | 192.168.16.255 | Default network (Linksys) |
| 192.168.123.0/24 | 192.168.123.0 | 192.168.123.255 | Default network (Sitecom) |
| 192.168.168.0/24 | 192.168.168.0 | 192.168.168.255 | Default network (SonicWall) |
| 192.168.223.0/24 | 192.168.223.0 | 192.168.223.255 | Default network (Trendnet) |
| 192.168.254.0/24 | 192.168.254.0 | 192.168.254.255 | Default network (Siemens, Actiontec) |