Visual lab
Learn subnetting visually
11 short lessons, from binary to IPv6. Change the inputs and watch every value update.
Lesson 5 of 11Intermediate
Split a network
Borrow bits, get subnets
Each bit you borrow from the host part doubles the number of subnets and halves their size.
You can also paste 10.44.20.0/23
/23
/25
From /24 to /27 (up to 4 bits borrowed)
Bits borrowed
2
/25 − /23
Subnets created
4
2^2
Addresses each
128
2^7
Usable hosts each
126
Minus network and broadcast
Subnet tree
Children never overlap. Each one is its own broadcast domain.
Parent
10.44.20.0/23
#100
10.44.20.0/25
128 addresses · 126 usable
#201
10.44.20.128/25
128 addresses · 126 usable
#310
10.44.21.0/25
128 addresses · 126 usable
#411
10.44.21.128/25
128 addresses · 126 usable
Address table
Green bits in the tree are the borrowed bits that number each subnet.
| # | Network | First usable | Last usable | Broadcast |
|---|---|---|---|---|
| 1 | 10.44.20.0/25 | 10.44.20.1 | 10.44.20.126 | 10.44.20.127 |
| 2 | 10.44.20.128/25 | 10.44.20.129 | 10.44.20.254 | 10.44.20.255 |
| 3 | 10.44.21.0/25 | 10.44.21.1 | 10.44.21.126 | 10.44.21.127 |
| 4 | 10.44.21.128/25 | 10.44.21.129 | 10.44.21.254 | 10.44.21.255 |
Lock it in
Drill the “Size for subnets” skill until it is automatic, or try the real tool.
Lesson 5 of 11
Next: On-link vs gateway