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/20 subnet mask
A /20 block has 4,096 addresses with the netmask 255.255.240.0. The size of each subnet in an AWS default VPC.
255.255.240.0| CIDR notation | /20 |
| Netmask | 255.255.240.0 |
| Wildcard mask | 0.0.15.255 |
| Total addresses | 4,096 |
| Usable hosts | 4,094 |
| Usable in an AWS subnet | 4,091 |
| Example range | 10.0.0.0/20: 10.0.0.0 to 10.0.15.255 |
How /20 fits with other sizes
- A /8 holds 4,096 subnets of /20.
- A /16 holds 16 subnets of /20.
- It splits into 2 subnets of /21.
- It splits into 4 subnets of /22.
- It splits into 16 subnets of /24.