4️⃣ IP addresses V4
The fourth version of the Internet Protocol (IP)
IP v4 addresses use the format xxx.xxx.xxx.xxx
Four sets of three digits ranging between 0-255 separated by a full stop. The number 0 and 255 are not usually used for IP addresses. Each set of digits is called an octet
Typically, addresses appear as:
192.168.1.1 - IP Address
255.255.255.0 - Subnet Mask
Part of the IP address relates to a network address and part to a node address. (Submet mask)
IP Address Classes#
The first octet of an IP address specifies which class an address belongs to
For each class of addresses a default subnet mask exists.
| IP Address (first octet) | Class | Default subnet mask |
|---|---|---|
| 1-126 | A | 225.0.0.0 |
| 128-191 | B | 225.225.0.0 |
| 192-223 | C | 225.225.225.0 |
Special IP addresses#
| IP Address | Detail |
|---|---|
| 10.0.0.0 | Private Class A |
| 172.16.0.0 - 172.31.255.255 | Private Class B |
| 192.168.0.0 - 192.168.255.255 | Private Class C |
| 169.254.. | Issued due to APIPA |
| 127.0.0.1 | Loopback test |
APIPA
Automatic Private IP Addressing
A feature available in Windows that caters for DHCP issues. If there are problems with the DHCP server and an IP Address cannot be obtained dynamically then a special class B address in the range of 169.254.*.* will be issued that given limited network functionality.