/4 vs /6 — Subnet Comparison
A /4 subnet is 4× larger than a /6. Every additional bit in the prefix halves the address space — the 2-bit difference between these two means /4 has 22 = 4 times as many addresses.
Key Differences
How 4 /6 Subnets Divide a /4
Example using 10.0.0.0/4 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 0.0.0.0/6 | 0.0.0.0 | 0.0.0.1 | 3.255.255.254 | 3.255.255.255 | 67,108,862 |
| 2 | 4.0.0.0/6 | 4.0.0.0 | 4.0.0.1 | 7.255.255.254 | 7.255.255.255 | 67,108,862 |
| 3 | 8.0.0.0/6 | 8.0.0.0 | 8.0.0.1 | 11.255.255.254 | 11.255.255.255 | 67,108,862 |
| 4 | 12.0.0.0/6 | 12.0.0.0 | 12.0.0.1 | 15.255.255.254 | 15.255.255.255 | 67,108,862 |
FAQ
What is the difference between /4 and /6?
A /4 has 268,435,454 usable hosts
and a /6 has 67,108,862.
The subnet masks differ: /4 uses 240.0.0.0
while /6 uses 252.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 2-bit gap means
/4 is exactly 4× larger.
How many /6 subnets fit in a /4?
Exactly 4 /6 subnets fit perfectly inside one /4 with no wasted space. To split a /4 into /6s, just increment the last 2 bits of the network address for each new subnet.
Which should I choose?
Choose based on how many hosts you need. Use the hosts → prefix calculator on the homepage to find the right size for your requirements.