Valid IP Address
- must be in the form of A.B.C.D,
- where A, B, C, and D are numbers from 0-255
- The numbers cannot be 0 prefixed unless they are 0.
Subnetting – the process of taking a large network and splitting it up into many individual smaller subnetworks or subnets.
Address classes give us a way to break the total global IP space into discrete networks.
Network ID – used to identify networks
Host ID – used to identify individual hosts.
Subnet ID
10.0.1.10 (10.0 is the network ID, 1.10 is the host ID)
In a world with subnetting, some bits that would normally comprise the host ID are actually used for the subnet ID.
Subnet Masks – 32-bit numbers that are normally written out as four octets in decimal
| IP Address | 9 | 100 | 100 | 100 |
| IP Address (in binary) | 0000 1001 | 0110 0100 | 0110 0100 | 0110 0100 |
| Subnet Mask (in binary) | 1111 1111 | 1111 1111 | 1111 1111 | 0000 0000 |
Each part of the IP Address is an octet, which means that it consists of eight bits.
The number 9 in binary is just 1001, but since each octet needs eight bits, we need to pad it with some zeros in front.
The size of a subnet is defined by the subnet mask.
A single 8-bit number can represent 256 different numbers, or more specifically, the number 0-255.
9.100.100.100, with subnet mask 255.255.255.224
- Since that subnet mask represents 27 ones followed by five zeros, a quicker way of referencing this is with the notation /27. The entire IP and subnet mask could be written out as 9.100.100.100/27.
Basic Binary Math
0 or 1, binary or base 2
Binary
| 32 | 16 | 08 | 04 | 02 | 01 |
| 1 | |||||
| 1 | 0 | ||||
| 1 | 1 | ||||
| 1 | 0 | 0 | |||
| 1 | 0 | 1 | |||
| 1 | 1 | 0 | |||
| 1 | 1 | 1 | |||
| 1 | 0 | 0 | 0 | ||
| 1 | 0 | 0 | 1 | ||
| 1 | 0 | 1 | 0 | ||
| 1 | 0 | 1 | 1 |
Decimal
| 10 | 01 |
| 1 | |
| 2 | |
| 3 | |
| 4 | |
| 5 | |
| 6 | |
| 7 | |
| 8 | |
| 9 | |
| 1 | 0 |
| 1 | 1 |
8\;bit\;is\;2^8 = 256
4\;bit\;is\;2^4 = 16
16\;bit\;is\;2^16\ = 65536
decimal – base 10
binary – base 2
In binary:
| 0 + 0 = 0 |
| 0 + 1 = 1 |
| 1 + 0 = 1 |
| 1 + 1 = 10 |
The basic equation is x or y = z. If either x or y is true, then z is true, otherwise, it’s false.
In Binary, 1 or 0 = but 0 or 0 equals 0. 1 and 1 = 1, but 1 and 0 = 0, 0 and 0 = 0.
