An IP Address is a unique numerical label assigned to each device connected to a computer network. It serves as both a host identifier and a location address.
Quick Comparison
- IPv4: 32-bit address, dot-decimal (e.g., 192.168.1.1).
- IPv6: 128-bit address, hexadecimal (e.g., 2001:db8::1).
Private IP Ranges (RFC 1918)
To preserve public IPv4 addresses, specific ranges are reserved for internal use within LANs.
| Class | Range | CIDR |
|---|---|---|
| Class A | 10.0.0.0 – 10.255.255.255 | 10.0.0.0/8 |
| Class B | 172.16.0.0 – 172.31.255.255 | 172.16.0.0/12 |
| Class C | 192.168.0.0 – 192.168.255.255 | 192.168.0.0/16 |
The Role of Subnet Masks
A subnet mask distinguishes the Network Part (street) from the Host Part (house number) of an IP address.
Example: 192.168.1.10 with mask 255.255.255.0
- Network: 192.168.1.0
- Host: .10
IPv4 Address Classes
| Class | Range (1st Octet) | Default Mask | Typical Usage |
|---|---|---|---|
| Class A | 1 – 126 | 255.0.0.0 | Large Enterprises / ISPs |
| Class B | 128 – 191 | 255.255.0.0 | Medium Companies / Universities |
| Class C | 192 – 223 | 255.255.255.0 | Small Businesses / Homes |
Reserved Addresses
127.0.0.1 is the loopback address used for self-testing. 0.0.0.0 is the "any" or default route address.