Introduction to IPv4
Nerd Cafe | نرد کافه
1. What is IPv4?
IPv4 addresses are 32 bits long, normally written as 4 octets in dotted decimal:
a.b.c.d(each octet 0–255).Example:
192.168.1.10= four 8-bit numbers.
2. IPv4 Address Classes
To organize networks efficiently, IPv4 addresses were historically divided into classes. These classes help define the network portion and host portion of the address. Here’s a breakdown:
A
0 – 127
255.0.0.0
N=8, H=24
~16.7 million
Very large networks
B
128 – 191
255.255.0.0
N=16, H=16
65,534
Medium networks
C
192 – 223
255.255.255.0
N=24, H=8
254
Small networks
D
224 – 239
N/A
Reserved
-
Multicast traffic
E
240 – 255
N/A
Reserved
-
Experimental / research
3. Binary Refresher (Bit Weights)
Each octet has 8 bit positions with weights:
128 64 32 16 8 4 2 1 (left to right).To convert a decimal octet to binary: subtract the largest weight that fits, mark a 1, continue.
Example: Convert 192 to binary (digit-by-digit):
Start with 192.
192 ≥ 128 → take 128. remainder = 192 − 128 = 64 → bit1 = 1.
64 ≥ 64 → take 64. remainder = 64 − 64 = 0 → bit2 = 1.
Remaining weights (32,16,8,4,2,1) are all > 0 remainder → bits = 0.
So binary =
11000000.
4. The Network vs Host Concept
IPv4 addresses are divided into:
Network portion – identifies the network.
Host portion – identifies the device (host) on that network.
Which bits are network and which are host depends on the subnet mask. Subnet masks look like this:
Or in binary:
The
1s cover the network bits.The
0s cover the host bits.
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Keywords
Network IP , Broadcast IP , First IP (usable) , Last IP (usable) , Number of available IPs (hosts) , Subnet mask , Nerd Cafe , نرد کافه
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