/20 vs /22 — Subnet Comparison
A /20 subnet is 4× larger than a /22. Every additional bit in the prefix halves the address space — the 2-bit difference between these two means /20 has 22 = 4 times as many addresses.
4K IPs — AWS default subnet size
Typical Uses
- →AWS default subnet (per AZ)
- →Medium-large application tier subnet
- →Office floor VLAN
1K IPs — medium site subnet
Typical Uses
- →Medium office floor VLAN
- →Application tier with ~500 hosts
- →Cloud subnet for a single microservice cluster
Key Differences
How 4 /22 Subnets Divide a /20
Example using 10.0.0.0/20 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/22 | 10.0.0.0 | 10.0.0.1 | 10.0.3.254 | 10.0.3.255 | 1,022 |
| 2 | 10.0.4.0/22 | 10.0.4.0 | 10.0.4.1 | 10.0.7.254 | 10.0.7.255 | 1,022 |
| 3 | 10.0.8.0/22 | 10.0.8.0 | 10.0.8.1 | 10.0.11.254 | 10.0.11.255 | 1,022 |
| 4 | 10.0.12.0/22 | 10.0.12.0 | 10.0.12.1 | 10.0.15.254 | 10.0.15.255 | 1,022 |
FAQ
What is the difference between /20 and /22?
A /20 has 4,094 usable hosts
and a /22 has 1,022.
The subnet masks differ: /20 uses 255.255.240.0
while /22 uses 255.255.252.0.
Every additional bit in the prefix halves the number of addresses — so the 2-bit gap means
/20 is exactly 4× larger.
How many /22 subnets fit in a /20?
Exactly 4 /22 subnets fit perfectly inside one /20 with no wasted space. To split a /20 into /22s, just increment the last 2 bits of the network address for each new subnet.
Which should I choose?
/20 is typically used for: AWS default subnet, medium office VLAN. /22 is better for: Medium office/application segment. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.