Visual lab
Learn subnetting visually
11 short lessons, from binary to IPv6. Change the inputs and watch every value update.
Test address
Used by lessons 2 to 4Tip: paste an address with a prefix, like 10.0.5.9/22
/25 · 255.255.255.128
Lesson 4 of 11Beginner
Bitwise AND
IP address AND subnet mask
A bit survives only where both the address and the mask have a 1. What survives is the network address.
Octet 4 is interesting
| Row | Octet 1 | Octet 2 | Octet 3 | Octet 4 |
|---|---|---|---|---|
| Address | 10 | 44 | 21 | 148 |
| Mask | 255 | 255 | 255 | 128 |
| Network | 10 | 44 | 21 | 128 |
Octet 4, bit by bit1 AND 1 = 1, anything else = 0
Place value1286432168421Dec
Address10010100148
Mask10000000128
Result10000000128
Network address
10.44.21.128/25
Usable range
10.44.21.129 – 10.44.21.254
Broadcast
10.44.21.255
Same network, same subnet
Every host whose address ANDs to 10.44.21.128 with this mask sits on the same local subnet. Routers and hosts do this calculation on every packet.Lock it in
Drill the “Network address” skill until it is automatic.
Lesson 4 of 11
Next: Split a network