IP Subnetting

Subnetting

Subnetting used in IP network for many years the purpose of subnetting Is to break IP networks into multiple chunks , IP Network subnetting can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic...

Subnet Masking

Applying a subnet mask to an IP address allows you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. Performing a bitwise logical AND operation between the IP address and the subnet mask results in the Network Address or Number.

For example, using our test IP address and the default Class B subnet mask, we get:

10001100.10110011.11110000.11001000      140.179.240.200   Class B IP Address

11111111.11111111.00000000.00000000      255.255.000.000   Default Class B Subnet Mask

--------------------------------------------------------

10001100.10110011.00000000.00000000      140.179.000.000   Network Address

Default subnet masks:

· Class A - 255.0.0.0 - 11111111.00000000.00000000.00000000

· Class B - 255.255.0.0 - 11111111.11111111.00000000.00000000

· Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000

Allowed Class A Subnet and Host IP addresses

# bits	Subnet Mask	CIDR	# Subnets	# Hosts	Nets * Hosts
2	255.192.0.0	/10	2	4194302	8388604
3	255.224.0.0	/11	6	2097150	12582900
4	255.240.0.0	/12	14	1048574	14680036
5	255.248.0.0	/13	30	524286	15728580
6	255.252.0.0	/14	62	262142	16252804
7	255.254.0.0	/15	126	131070	16514820
8	255.255.0.0	/16	254	65534	16645636
9	255.255.128.0	/17	510	32766	16710660
10	255.255.192.0	/18	1022	16382	16742404
11	255.255.224.0	/19	2046	8190	16756740
12	255.255.240.0	/20	4094	4094	16760836
13	255.255.248.0	/21	8190	2046	16756740
14	255.255.252.0	/22	16382	1022	16742404
15	255.255.254.0	/23	32766	510	16710660
16	255.255.255.0	/24	65534	254	16645636
17	255.255.255.128	/25	131070	126	16514820
18	255.255.255.192	/26	262142	62	16252804
19	255.255.255.224	/27	524286	30	15728580
20	255.255.255.240	/28	1048574	14	14680036
21	255.255.255.248	/29	2097150	6	12582900
22	255.255.255.252	/30	4194302	2	8388604

Allowed Class B Subnet and Host IP addresses

# bits	Subnet Mask	CIDR	# Subnets	# Hosts	Nets * Hosts
2	255.255.192.0	/18	2	16382	32764
3	255.255.224.0	/19	6	8190	49140
4	255.255.240.0	/20	14	4094	57316
5	255.255.248.0	/21	30	2046	61380
6	255.255.252.0	/22	62	1022	63364
7	255.255.254.0	/23	126	510	64260
8	255.255.255.0	/24	254	254	64516
9	255.255.255.128	/25	510	126	64260
10	255.255.255.192	/26	1022	62	63364
11	255.255.255.224	/27	2046	30	61380
12	255.255.255.240	/28	4094	14	57316
13	255.255.255.248	/29	8190	6	49140
14	255.255.255.252	/30	16382	2	32764

Allowed Class C Subnet and Host IP addresses

# bits	Subnet Mask	CIDR	# Subnets	# Hosts	Nets * Hosts
2	255.255.255.192	/26	2	62	124
3	255.255.255.224	/27	6	30	180
4	255.255.255.240	/28	14	14	196
5	255.255.255.248	/29	30	6	180
6	255.255.255.252	/30	62	2	124

Logical Operations

This page will provide a brief review and explanation of the common logical bitwise operations AND, OR, XOR (Exclusive OR) and NOT. Logical operations are performed between two data bits (except for NOT). Bits can be either "1" or "0", and these operations are essential to performing digital math operations.
In the "truth tables" below, the input bits are in bold, and the results are plain.

AND

The logical AND operation compares 2 bits and if they are both "1", then the result is "1", otherwise, the result is "0".

	0	1
0	0	0
1	0	1

OR

The logical OR operation compares 2 bits and if either or both bits are "1", then the result is "1", otherwise, the result is "0".

	0	1
0	0	1
1	1	1

XOR

The logical XOR (Exclusive OR) operation compares 2 bits and if exactly one of them is "1" (i.e., if they are different values), then the result is "1"; otherwise (if the bits are the same), the result is "0".

	0	1
0	0	1
1	1	0

NOT

The logical NOT operation simply changes the value of a single bit. If it is a "1", the result is "0"; if it is a "0", the result is "1". Note that this operation is different in that instead of comparing two bits, it is acting on a single bit.

0	1
1	0

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