IPRangeExplorer

/25 vs /29 — Subnet Comparison

A /25 subnet is 16× larger than a /29. Every additional bit in the prefix halves the address space — the 4-bit difference between these two means /25 has 24 = 16 times as many addresses.

/25

126 usable hosts — half a /24

Full reference →
Total IPs 128
Usable Hosts 126
Subnet Mask 255.255.255.128
Wildcard Mask 0.0.0.127

Typical Uses

  • →Public vs private half of a /24
  • →Department sub-segment
  • →Smaller cloud application subnets
/29

6 usable hosts — tiny cluster

Full reference →
Total IPs 8
Usable Hosts 6
Subnet Mask 255.255.255.248
Wildcard Mask 0.0.0.7

Typical Uses

  • →Small server cluster (web + app + db)
  • →Infrastructure management segment
  • →Very small office or branch

Key Differences

16×
more IPs in /25 than /29
16
/29 subnets fit inside one /25
4
bits of difference in prefix length

How 16 /29 Subnets Divide a /25

Example using 10.0.0.0/25 as the parent block.

# CIDR Network First Usable Last Usable Broadcast Hosts
1 10.0.0.0/29 10.0.0.0 10.0.0.1 10.0.0.6 10.0.0.7 6
2 10.0.0.8/29 10.0.0.8 10.0.0.9 10.0.0.14 10.0.0.15 6
3 10.0.0.16/29 10.0.0.16 10.0.0.17 10.0.0.22 10.0.0.23 6
4 10.0.0.24/29 10.0.0.24 10.0.0.25 10.0.0.30 10.0.0.31 6
5 10.0.0.32/29 10.0.0.32 10.0.0.33 10.0.0.38 10.0.0.39 6
6 10.0.0.40/29 10.0.0.40 10.0.0.41 10.0.0.46 10.0.0.47 6
7 10.0.0.48/29 10.0.0.48 10.0.0.49 10.0.0.54 10.0.0.55 6
8 10.0.0.56/29 10.0.0.56 10.0.0.57 10.0.0.62 10.0.0.63 6
9 10.0.0.64/29 10.0.0.64 10.0.0.65 10.0.0.70 10.0.0.71 6
10 10.0.0.72/29 10.0.0.72 10.0.0.73 10.0.0.78 10.0.0.79 6
11 10.0.0.80/29 10.0.0.80 10.0.0.81 10.0.0.86 10.0.0.87 6
12 10.0.0.88/29 10.0.0.88 10.0.0.89 10.0.0.94 10.0.0.95 6
13 10.0.0.96/29 10.0.0.96 10.0.0.97 10.0.0.102 10.0.0.103 6
14 10.0.0.104/29 10.0.0.104 10.0.0.105 10.0.0.110 10.0.0.111 6
15 10.0.0.112/29 10.0.0.112 10.0.0.113 10.0.0.118 10.0.0.119 6
16 10.0.0.120/29 10.0.0.120 10.0.0.121 10.0.0.126 10.0.0.127 6

FAQ

What is the difference between /25 and /29?

A /25 has 126 usable hosts and a /29 has 6. The subnet masks differ: /25 uses 255.255.255.128 while /29 uses 255.255.255.248. Every additional bit in the prefix halves the number of addresses — so the 4-bit gap means /25 is exactly 16× larger.

How many /29 subnets fit in a /25?

Exactly 16 /29 subnets fit perfectly inside one /25 with no wasted space. To split a /25 into /29s, just increment the last 4 bits of the network address for each new subnet.

Which should I choose?

/25 is typically used for: Half a /24 — public/private split. /29 is better for: Tiny server cluster or infra segment. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.

Related Comparisons

/24 vs /25 /25 vs /26 /28 vs /29 /29 vs /30