Subnet for 2000 hosts
A network that needs 2000 hosts fits in a /21, mask 255.255.248.0, with 2,046 usable addresses.
A network built for 2000 hosts needs a /21. The mask is 255.255.248.0, and its 2,046 usable addresses leave 46 spare for growth.
The next smaller block, a /22, only allows 1,022 usable addresses, which is not enough for 2000 hosts. That makes /21 the smallest block that fits.
Enter any address below to see the exact network, broadcast, and host range for a /21 block.
Calculate a /21 network
Accepts CIDR (192.0.2.0/24), IP + mask (192.0.2.0 255.255.255.0), or a bare IP (defaults to /24).
11000000.00000000.00000010.0000000011111111.11111111.11111000.00000000Example: 192.0.2.0/21
Taking 192.0.2.0/21 as a worked example, a /21 block breaks down like this:
| Network address | 192.0.0.0 |
|---|---|
| Usable range | 192.0.0.1 - 192.0.7.254 |
| Broadcast address | 192.0.7.255 |
| Total addresses | 2,048 |
| Usable hosts | 2,046 |
Frequently asked questions
What subnet mask do I need for 2000 hosts?
A network with 2000 hosts fits in a /21, which uses the mask 255.255.248.0 and provides 2,046 usable addresses.
How many addresses does a /21 block have in total?
A /21 has 2,048 total addresses, 2,046 of them usable (the total minus the network and broadcast addresses, except for /31 and /32).
Does a /21 waste any addresses for 2000 hosts?
Yes, 46 addresses of headroom. A /21 provides 2,046 usable addresses for the 2000 you need, and the next smaller block, a /22, does not hold enough.
How do I work this out myself?
Find the smallest power of two, minus two, that is at least 2000. That takes 11 host bits, which leaves a /21 prefix. See how to calculate a subnet mask for the full method.