IP ADDRESSING Lecture 2: IP addressing Networks and Communication Department 1.
Ip Addressing
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IP ADDRESSING An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation. Example: 140.179.220.200 It is sometimes useful to view the values in their binary form. 140 . 179 . 220 . 200 10001100.10110011.11011100.11001000 Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address. Address Classes: There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address. • Class A addresses begin with 0xxx, or 1 to 126 decimal. • Class B addresses begin with 10xx, or 128 to 191 decimal. • Class C addresses begin with 110x, or 192 to 223 decimal. • Class D addresses begin with 1110, or 224 to 239 decimal. • Class E addresses begin with 1111, or 240 to 254 decimal. Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine; [You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting; Class E addresses are reserved for future use. They should not be used for host addresses. Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N, in blue) and which part belongs to the node (n, in red). • Class A -- NNNNNNNN.nnnnnnnn.nnnnnnnn.nnnnnnnn • Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn • Class C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn In the example, 140.179.220.200 is a Class B address so by default the Network part of the address (also known as the Network Address) is defined by the first two octets (140.179.x.x) and the node part is defined by the last 2 octets (x.x.220.200).
description
IP ADDRESSING, SUBNETTING, CLASSES AND DESCRIBTION, SUPERNETTING ETC...........
Transcript of Ip Addressing
IP ADDRESSING
An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation.
Example: 140.179.220.200
It is sometimes useful to view the values in their binary form.
140 . 179 . 220 . 200 10001100.10110011.11011100.11001000
Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address.
Address Classes:
There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.
• Class A addresses begin with 0xxx, or 1 to 126 decimal. • Class B addresses begin with 10xx, or 128 to 191 decimal. • Class C addresses begin with 110x, or 192 to 223 decimal. • Class D addresses begin with 1110, or 224 to 239 decimal. • Class E addresses begin with 1111, or 240 to 254 decimal.
Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine; [You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting; Class E addresses are reserved for future use. They should not be used for host addresses.
Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N, in blue) and which part belongs to the node (n, in red).
• Class A -- NNNNNNNN.nnnnnnnn.nnnnnnnn.nnnnnnnn • Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn • Class C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn
In the example, 140.179.220.200 is a Class B address so by default the Network part of the address (also known as the Network Address) is defined by the first two octets (140.179.x.x) and the node part is defined by the last 2 octets (x.x.220.200).
In order to specify the network address for a given IP address, the node section is set to all "0"s. In our example, 140.179.0.0 specifies the network address for 140.179.220.200. When the node section is set to all "1"s, it specifies a broadcast that is sent to all hosts on the network. 140.179.255.255 specifies the example broadcast address. Note that this is true regardless of the length of the node section.
Private Subnets
There are three IP network addresses reserved for private networks. The addresses are 10.0.0.0, Subnet Mask 255.0.0.0, 172.16.0.0, Subnet Mask 255.240.0.0, and 192.168.0.0, Subnet Mask 255.255.0.0. These addresses are also notated 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; this notation will be explained later in this tutorial. They can be used by anyone setting up internal IP networks, such as a lab or home LAN behind a NAT or proxy server or a router. It is always safe to use these because routers on the Internet by default will never forward packets coming from these addresses.
SUBNETTING
Subnetting is the process of dividing a network of any classful IP network (A, B, or C) into smaller networks. Subnetting an IP Network 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. In an Ethernet network, all nodes on a segment see all the packets transmitted by all the other nodes on that segment. Performance can be adversely affected under heavy traffic loads, due to collisions and the resulting retransmissions. A router is used to connect IP networks to minimize the amount of traffic each segment must receive.
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
Additional bits can be added to the default subnet mask for a given Class to further subnet, or break down, a network. When a bitwise logical AND operation is performed between the subnet mask and IP address, the result defines the Subnet Address (also called the Network Address or Network Number). There are some restrictions on the subnet address. Node addresses of all "0"s and all "1"s are reserved for specifying the local network (when a host does not know its network address) and all hosts on the network (broadcast address), respectively. This also applies to subnets. A subnet address cannot be all "0"s or all "1"s. This also implies that a 1 bit subnet mask is not allowed. This restriction is required because older standards enforced this restriction. Recent standards that allow use of these subnets have superseded these standards, but many "legacy" devices do not support the newer standards. If you are operating in a controlled environment, such as a lab, you can safely use these restricted subnets.
Additional bits can be added to the default subnet mask for a given Class to further subnet, or break down, a network. When a bitwise logical AND operation is performed between the subnet mask and IP address, the result defines the Subnet Address (also called the Network Address or Network Number). There are some restrictions on the subnet address. Node addresses of all "0"s and all "1"s are reserved for specifying the local network (when a host does not know its network address) and all hosts on the network (broadcast address), respectively. This also applies to subnets. A subnet address cannot be all "0"s or all "1"s. This also implies that a 1 bit subnet mask is not allowed. This restriction is required because older standards enforced this restriction. Recent standards that allow use of these subnets have superseded these standards, but many "legacy" devices do not support the newer standards. If you are operating in a controlled environment, such as a lab, you can safely use these restricted subnets.
To calculate the number of subnets or nodes, use the formula (2n-2) where n = number of bits in either field, and 2n represents 2 raised to the nth power. Multiplying the number of subnets by the number of nodes available per subnet gives you the total number of nodes available for your class and subnet mask. Also, note that although subnet masks with non-contiguous mask bits are allowed, they are not recommended.
Example:
10001100.10110011.11011100.11001000 140.179.220.200 IP Address
11111111.11111111.11100000.00000000 255.255.224.000 Subnet Mask
--------------------------------------------------------
10001100.10110011.11000000.00000000 140.179.192.000 Subnet Address
10001100.10110011.11011111.11111111 140.179.223.255 Broadcast Address
In this example a 3 bit subnet mask was used. There are 6 (23-2) subnets available with this size mask (remember that subnets with all 0's and all 1's are not allowed). Each subnet has 8190 (213-2) nodes. Each subnet can have nodes assigned to any address between the Subnet address and the
Broadcast address. This gives a total of 49,140 nodes for the entire class B address subnetted this way. Notice that this is less than the 65,534 nodes an unsubnetted class B address would have.
You can calculate the Subnet Address by performing a bitwise logical AND operation between the IP address and the subnet mask, then setting all the host bits to 0s. Similarly, you can calculate the Broadcast Address for a subnet by performing the same logical AND between the IP address and the subnet mask, then setting all the host bits to 1s. That is how these numbers are derived in the example above.
CLASS C SUBNETTING
To make things easy, you may remember this.
� If all the bits in the host part are "0", that represents the network id. � If all the bits in the host part are "0" except the last bit, it is the first usable IP address. � If all the bits in the host part are "1" except the last bit, it is the last usable IP address. � If all the bits in the host part are "1", that represents the direct broadcast address. � All the IP addresses between the first and last IP addresses (including the first and last) can be
used to configure the devices
If we take an example for a Class C network, 192.168.10.0, the address part and the subnet mask can be represented as below
Component Binary Decimal Address Part
11000000.10101000.00001010.00000000 192.168.10.0
SN Mask 11111111.11111111.11111111.00000000 255.255.255.0
For a Class C IP address, the first three octets are used to represent the Network part and the last octet is used to represent the host part. From the above table, we can see all "1" in the network part and all "0" in the host part. When this subnet mask is converted to a decimals, it will become 255.2555.255.0. The default subnet mask for a Class C network is 255.255.255.0, Class B network is 255.255.0.0 and Class A network is 255.0.0.0
CLASS C - ONE BIT SUBNETTING :
Consider the network shown above. If we include one bit from the host part to the network part, the subnet mask is changed into 255.255.255.128. The single bit can have two values in last octet, either 0 or 1.
11000000.10101000.00001010.0 | 0000000 11111111.11111111.11111111.1 | 0000000
That means, we can get two subnets if we do a single bit subnetting.
SN No
Description
Binaries
Decimal
1
Network Address 11000000.10101000.00001010.00000000 192.168.10.0
First IP Address 11000000.10101000.00001010.00000001 192.168.10.1
Last IP Address 11000000.10101000.00001010.01111110 192.168.10.126
Broadcast Address 11000000.10101000.00001010.01111111 192.168.10.127
2
Network Address 11000000.10101000.00001010.10000000 192.168.10.128
First IP Address 11000000.10101000.00001010.10000001 192.168.10.129
Last IP Address 11000000.10101000.00001010.11111110 192.168.10.224
Broadcast Address 11000000.10101000.00001010.11111111 192.168.10.225
The network 192.168.10.0 is divided into two networks, each network has 128 total IP addresses and 126 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id). The subnet mask for one bit subnetting is 255.255.255.128.
CLASS C - TWO BIT SUBNETTING :
If we include two bits from the host part to the network part, the subnet mask is changed into
255.255.255.192. The two bits added to network part can have four possible values in last octet and
that are 00, 01, 10 and 11. That means, we can get four networks if we do a two bit subnetting.
11000000.10101000.00001010.00 | 000000
11111111.11111111.11111111.11 | 000000
SN No Description
Binaries
Decimal
1
Network Address 11000000.10101000.00001010.00000000 192.168.10.0
First IP Address 11000000.10101000.00001010.00000001 192.168.10.1
Last IP Address 11000000.10101000.00001010.00111110 192.168.10.62
Broadcast Address 11000000.10101000.00001010.00111111 192.168.10.63
2
Network Address 11000000.10101000.00001010.01000000 192.168.10.64
First IP Address 11000000.10101000.00001010.01000001 192.168.10.65
Last IP Address 11000000.10101000.00001010.01111110 192.168.10.126
Broadcast Address 11000000.10101000.00001010.01111111 192.168.10.127
3
Network Address 11000000.10101000.00001010.10000000 192.168.10.128
First IP Address 11000000.10101000.00001010.10000001 192.168.10.129
Last IP Address 11000000.10101000.00001010.10111110 192.168.10.190
Broadcast Address 11000000.10101000.00001010.10111111 192.168.10.191
4
Network Address 11000000.10101000.00001010.11000000 192.168.10.192
First IP Address 11000000.10101000.00001010.11000001 192.168.10.193
Last IP Address 11000000.10101000.00001010.11111110 192.168.10.254
Broadcast Address 11000000.10101000.00001010.11111111 192.168.10.255
The network 192.168.10.0 is divided into four networks, each network has 64 total IP addresses and
62 usable IP addresses (two IP addresses are used in each subnet to represent the network id and
the broadcast id). The subnet mask for two bit subnetting is 255.255.255.192
CLASS C - 3 BIT SUBNETTING :
If we include three bits from the host part to the network part, the subnet mask is changed into 255.255.255.224. The three bits added to network part can have eight possible values in last octet and that are 000, 001, 010, 011, 100, 101, 110 and 111. That means, we can get eight networks if we do a three bit subnetting.
11000000.10101000.00001010.000 | 00000 11111111.11111111.11111111.111 | 00000
SN No
Description
Binaries
Decimal
1
Network Address 11000000.10101000.00001010.00000000 192.168.10.0
First IP Address 11000000.10101000.00001010.00000001 192.168.10.1
Last IP Address 11000000.10101000.00001010.00011110 192.168.10.30
Broadcast Address 11000000.10101000.00001010.00011111 192.168.10.31
2
Network Address 11000000.10101000.00001010.00100000 192.168.10.32
First IP Address 11000000.10101000.00001010.00100001 192.168.10.33
Last IP Address 11000000.10101000.00001010.00111110 192.168.10.62
Broadcast Address 11000000.10101000.00001010.00111111 192.168.10.63
3
Network Address 11000000.10101000.00001010.01000000 192.168.10.64
First IP Address 11000000.10101000.00001010.01000001 192.168.10.65
Last IP Address 11000000.10101000.00001010.01011110 192.168.10.94
Broadcast Address 11000000.10101000.00001010.01011111 192.168.10.95
4
Network Address 11000000.10101000.00001010.01100000 192.168.10.96
First IP Address 11000000.10101000.00001010.01100001 192.168.10.97
Last IP Address 11000000.10101000.00001010.01111110 192.168.10.126
Broadcast Address 11000000.10101000.00001010.01111111 192.168.10.127
5
Network Address 11000000.10101000.00001010.10000000 192.168.10.128
First IP Address 11000000.10101000.00001010.10000001 192.168.10.129
Last IP Address 11000000.10101000.00001010.10011110 192.168.10.158
Broadcast Address 11000000.10101000.00001010.10011111 192.168.10.159
6
Network Address 11000000.10101000.00001010.10100000 192.168.10.160
First IP Address 11000000.10101000.00001010.10100001 192.168.10.161
Last IP Address 11000000.10101000.00001010.10111110 192.168.10.190
Broadcast Address 11000000.10101000.00001010.10111111 192.168.10.191
7
Network Address 11000000.10101000.00001010.11000000 192.168.10.192
First IP Address 11000000.10101000.00001010.11000001 192.168.10.193
Last IP Address 11000000.10101000.00001010.11011110 192.168.10.222
Broadcast Address 11000000.10101000.00001010.11011111 192.168.10.223
8 Network Address 11000000.10101000.00001010.11100000 192.168.10.224
First IP Address 11000000.10101000.00001010.11100001 192.168.10.225
Last IP Address 11000000.10101000.00001010.11111110 192.168.10.254
Broadcast Address 11000000.10101000.00001010.11111111 192.168.10.255
The network 192.168.10.0 is divided into eight networks, each network has 32 total IP addresses and 30 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id). The subnet mask for three bit subnetting is 255.255.255.224.
CLASS C - 4 BIT SUBNETTING :
If we include four bits from the host part to the network part, the subnet mask is changed to 255.255.255.240.
11000000.10101000.00001010.0000 | 0000 11111111.11111111.11111111.1111 | 0000
The four bits added to network part can have sixteen possible values in last (fourth) octet and that are 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111.
SN No
Description
Binaries
Decimal
1
Network Address 11000000.10101000.00001010.00000000 192.168.10.0
First IP Address 11000000.10101000.00001010.00000001 192.168.10.1
Last IP Address 11000000.10101000.00001010.00001110 192.168.10.14
Broadcast Address 11000000.10101000.00001010.00001111 192.168.10.15
2
Network Address 11000000.10101000.00001010.00010000 192.168.10.16
First IP Address 11000000.10101000.00001010.00010001 192.168.10.17
Last IP Address 11000000.10101000.00001010.00011110 192.168.10.30
Broadcast Address 11000000.10101000.00001010.00011111 192.168.10.31
3
Network Address 11000000.10101000.00001010.00100000 192.168.10.32
First IP Address 11000000.10101000.00001010.00100001 192.168.10.33
Last IP Address 11000000.10101000.00001010.00101110 192.168.10.46
Broadcast Address 11000000.10101000.00001010.00101111 192.168.10.47
4
Network Address 11000000.10101000.00001010.00110000 192.168.10.48
First IP Address 11000000.10101000.00001010.00110001 192.168.10.49
Last IP Address 11000000.10101000.00001010.00111110 192.168.10.62
Broadcast Address 11000000.10101000.00001010.00111111 192.168.10.63
5
Network Address 11000000.10101000.00001010.01000000 192.168.10.64
First IP Address 11000000.10101000.00001010.01000001 192.168.10.65
Last IP Address 11000000.10101000.00001010.01001110 192.168.10.78
Broadcast Address 11000000.10101000.00001010.01001111 192.168.10.79
6
Network Address 11000000.10101000.00001010.01010000 192.168.10.80
First IP Address 11000000.10101000.00001010.01010001 192.168.10.81
Last IP Address 11000000.10101000.00001010.01011110 192.168.10.94
Broadcast Address 11000000.10101000.00001010.01011111 192.168.10.95
7
Network Address 11000000.10101000.00001010.01100000 192.168.10.96
First IP Address 11000000.10101000.00001010.01100001 192.168.10.97
Last IP Address 11000000.10101000.00001010.01101110 192.168.10.110
Broadcast Address 11000000.10101000.00001010.01101111 192.168.10.111
8
Network Address 11000000.10101000.00001010.01110000 192.168.10.112
First IP Address 11000000.10101000.00001010.01110001 192.168.10.113
Last IP Address 11000000.10101000.00001010.01111110 192.168.10.126
Broadcast Address 11000000.10101000.00001010.01111111 192.168.10.127
9
Network Address 11000000.10101000.00001010.10000000 192.168.10.128
First IP Address 11000000.10101000.00001010.10000001 192.168.10.129
Last IP Address 11000000.10101000.00001010.10001110 192.168.10.142
Broadcast Address 11000000.10101000.00001010.10001111 192.168.10.143
10 Network Address 11000000.10101000.00001010.10010000 192.168.10.144
First IP Address 11000000.10101000.00001010.10010001 192.168.10.145
Last IP Address 11000000.10101000.00001010.10011110 192.168.10.158
Broadcast Address 11000000.10101000.00001010.10011111 192.168.10.159
11
Network Address 11000000.10101000.00001010.10100000 192.168.10.160
First IP Address 11000000.10101000.00001010.10100001 192.168.10.161
Last IP Address 11000000.10101000.00001010.10101110 192.168.10.174
Broadcast Address 11000000.10101000.00001010.10101111 192.168.10.175
12
Network Address 11000000.10101000.00001010.10110000 192.168.10.176
First IP Address 11000000.10101000.00001010.10110001 192.168.10.177
Last IP Address 11000000.10101000.00001010.10111110 192.168.10.190
Broadcast Address 11000000.10101000.00001010.10111111 192.168.10.191
13
Network Address 11000000.10101000.00001010.11000000 192.168.10.192
First IP Address 11000000.10101000.00001010.11000001 192.168.10.193
Last IP Address 11000000.10101000.00001010.11001110 192.168.10.206
Broadcast Address 11000000.10101000.00001010.11001111 192.168.10.207
14
Network Address 11000000.10101000.00001010.11010000 192.168.10.208
First IP Address 11000000.10101000.00001010.11010001 192.168.10.209
Last IP Address 11000000.10101000.00001010.11011110 192.168.10.222
Broadcast Address 11000000.10101000.00001010.11011111 192.168.10.223
15
Network Address 11000000.10101000.00001010.11100000 192.168.10.224
First IP Address 11000000.10101000.00001010.11100001 192.168.10.225
Last IP Address 11000000.10101000.00001010.11101110 192.168.10.238
Broadcast Address 11000000.10101000.00001010.11101111 192.168.10.239
16
Network Address 11000000.10101000.00001010.11110000 192.168.10.240
First IP Address 11000000.10101000.00001010.11110001 192.168.10.241
Last IP Address 11000000.10101000.00001010.11111110 192.168.10.254
Broadcast Address 11000000.10101000.00001010.11111111 192.168.10.255
The network 192.168.10.0 is divided into sixteen networks, each network has 16 total IP addresses and 14 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id).
From the above examples, you can can clearly understand how to subnet a Class C subnet.
Class C Subnetting can be summerized as below.
Subnet Bits
Subnet Mask CIDR Total Subnets
Usable IPs/Subnet
0 255.255.255.0 /24 1 254
1 255.255.255.128 /25 2 126
2 255.255.255.192 /26 4 62
3 255.255.255.224 /27 8 30
4 255.255.255.240 /28 16 14
5 255.255.255.248 /29 32 6
6 255.255.255.252 /30 64 2
CLASS B SUBNETTING
Remember, the first two octets of a Class B network is used to represent the network and the last two octets are used to represent the host. The default format for a Class B IP address is Network.Network.Host.Host.
Let us consider an example of Class B network 172.16.0.0 - 255.255.0.0. The binary representation of the above network and subnet mask is
Component Binary Decimal
Address Part 10101100.00010000.00000000.00000000 172.16.0.0
SN Mask 11111111.11111111.00000000.00000000 255.255.0.0
Once again,
� If all the bits in the host part are "0", that represents the network id. � If all the bits in the host part are "0" except the last bit, it is the first usable IP address. � If all the bits in the host part are "1" except the last bit, it is the last usable IP address.
� If all the bits in the host part are "1", that represents the direct broadcat address. � All the IP addresses between the first and last IP addresses (including the first and last) can be
used to configure the devices.
CLASS B - ONE BIT SUBNETTING :
If we include one bit from the host part to the network part, the subnet mask is changed into 255.255.128.0 The single bit can have two values in third octet, either 0 or 1.
10101100.00010000.0 | 0000000.00000000 11111111.11111111.1 | 0000000.00000000
That means, we can get two subnets if we do a single bit subnetting.
SN No
Description
Binaries
Decimal
1
Network Address 10101100.00010000.00000000.00000000 172.16.0.0
First IP Address 10101100.00010000.00000000.00000001 172.16.0.1
Last IP Address 10101100.00010000.01111111.11111110 172.16.127.254
Broadcast Address 10101100.00010000.01111111.11111111 172.16.127.255
2
Network Address 10101100.00010000.10000000.00000000 172.16.128.0
First IP Address 10101100.00010000.10000000.00000001 172.16.128.1
Last IP Address 10101100.00010000.11111111.11111110 172.16.255.254
Broadcast Address 10101100.00010000.11111111.11111111 172.16.255.255
The network 172.16.0.0 is divided into two networks, each network has 32768 total IP addresses and 32766 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id). The subnet mask for one bit subnetting is 255.255.128.0.
CLASS B - TWO BIT SUBNETTING :
If we include two bits from the host part to the network part, the subnet mask is changed into 255.255.192.0. The two bits added to network part can have four possible values in third octet, 00, 01, 10, and 11.
10101100.00010000.00 | 000000.00000000 11111111.11111111.11 | 000000.00000000
That means, we can get four networks if we do a two bit subnetting.
SN No
Description
Binaries
Decimal
1
Network Address 10101100.00010000.00000000.00000000 172.16.0.0
First IP Address 10101100.00010000.00000000.00000001 172.16.0.1
Last IP Address 10101100.00010000.00111111.11111110 172.16.63.254
Broadcast Address 10101100.00010000.00111111.11111111 172.16.63.255
2
Network Address 10101100.00010000.01000000.00000000 172.16.64.0
First IP Address 10101100.00010000.01000000.00000001 172.16.64.1
Last IP Address 10101100.00010000.01111111.11111110 172.16.127.254
Broadcast Address 10101100.00010000.01111111.11111111 172.16.127.255
3
Network Address 10101100.00010000.10000000.00000000 172.16.128.0
First IP Address 10101100.00010000.10000000.00000001 172.16.128.1
Last IP Address 10101100.00010000.10111111.11111110 172.16.191.254
Broadcast Address 10101100.00010000.10111111.11111111 172.16.191.255
4
Network Address 10101100.00010000.11000000.00000000 172.16.192.0
First IP Address 10101100.00010000.11000000.00000001 172.16.192.1
Last IP Address 10101100.00010000.11111111.11111110 172.16.255.254
Broadcast Address 10101100.00010000.11111111.11111111 172.16.255.255
The network 172.16.0.0 is divided into four networks, each network has 16384 total IP addresses and 16382 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id). The subnet mask for one bit subnetting is 255.255.192.0.
CLASS B - 3 BIT SUBNETTING :
If we include three bits from the host part to the network part, the subnet mask is changed into 255.255.224.0 The three bits added to network part can have eight possible values in the third octet and that are 000, 001, 010, and 011, 100, 101, 110 and 111.
10101100.00010000.000 | 00000.00000000 11111111.11111111.111 | 00000.00000000
That means, we can get eight networks if we do a three bit subnetting.
SN No
Description
Binaries
Decimal
1
Network Address 10101100.00010000.00000000.00000000 172.16.0.0
First IP Address 10101100.00010000.00000000.00000001 172.16.0.1
Last IP Address 10101100.00010000.00011111.11111110 172.16.31.254
Broadcast Address 10101100.00010000.00011111.11111111 172.16.31.255
2
Network Address 10101100.00010000.00100000.00000000 172.16.32.0
First IP Address 10101100.00010000.00100000.00000001 172.16.32.1
Last IP Address 10101100.00010000.00111111.11111110 172.16.63.254
Broadcast Address 10101100.00010000.00111111.11111111 172.16.63.255
3
Network Address 10101100.00010000.01000000.00000000 172.16.64.0
First IP Address 10101100.00010000.01000000.00000001 172.16.64.1
Last IP Address 10101100.00010000.01011111.11111110 172.16.95.254
Broadcast Address 10101100.00010000.01011111.11111111 172.16.95.255
4
Network Address 10101100.00010000.01100000.00000000 172.16.96.0
First IP Address 10101100.00010000.01100000.00000001 172.16.96.1
Last IP Address 10101100.00010000.01111111.11111110 172.16.127.254
Broadcast Address 10101100.00010000.01111111.11111111 172.16.127.255
5 Network Address 10101100.00010000.10000000.00000000 172.16.128.0
First IP Address 10101100.00010000.10000000.00000001 172.16.128.1
Last IP Address 10101100.00010000.10011111.11111110 172.16.159.254
Broadcast Address 10101100.00010000.10011111.11111111 172.16.159.255
6
Network Address 10101100.00010000.10100000.00000000 172.16.160.0
First IP Address 10101100.00010000.10100000.00000001 172.16.160.1
Last IP Address 10101100.00010000.10111111.11111110 172.16.191.254
Broadcast Address 10101100.00010000.10111111.11111111 172.16.191.255
7
Network Address 10101100.00010000.11000000.00000000 172.16.192.0
First IP Address 10101100.00010000.11000000.00000001 172.16.192.1
Last IP Address 10101100.00010000.11011111.11111110 172.16.223.254
Broadcast Address 10101100.00010000.11011111.11111111 172.16.223.255
8
Network Address 10101100.00010000.11100000.00000000 172.16.224.0
First IP Address 10101100.00010000.11100000.00000001 172.16.224.1
Last IP Address 10101100.00010000.11111111.11111110 172.16.255.254
Broadcast Address 10101100.00010000.11111111.11111111 172.16.255.255
The network 172.16.0.0 is divided into eight networks, each network has 8192 total IP addresses and 8190 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id).
CLASS B - 4 BIT SUBNETTING:
If we include four bits from the host part to the network part, the subnet mask is changed to 255.255.240.0.
10101100.00010000.0000 | 0000.00000000 11111111.11111111.1111 | 0000.00000000
The four bits added to network part can have sixteen possible values in third octet and that are 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111.
SN No
Description
Binaries
Decimal
1
Network Address 10101100.00010000.00000000.00000000 172.16.0.0
First IP Address 10101100.00010000.00000000.00000001 172.16.0.1
Last IP Address 10101100.00010000.00001111.11111110 172.16.15.254
Broadcast Address 10101100.00010000.00001111.11111111 172.16.15.255
2
Network Address 10101100.00010000.00010000.00000000 172.16.16.0
First IP Address 10101100.00010000.00010000.00000001 172.16.16.1
Last IP Address 10101100.00010000.00011111.11111110 172.16.31.254
Broadcast Address 10101100.00010000.00011111.11111111 172.16.31.255
3
Network Address 10101100.00010000.00100000.00000000 172.16.32.0
First IP Address 10101100.00010000.00100000.00000001 172.16.32.01
Last IP Address 10101100.00010000.00101111.11111110 172.16.47.254
Broadcast Address 10101100.00010000.00101111.11111111 172.16.47.255
4
Network Address 10101100.00010000.00110000.00000000 172.16.48.0
First IP Address 10101100.00010000.00110000.00000001 172.16.48.1
Last IP Address 10101100.00010000.00111111.11111110 172.16.63.254
Broadcast Address 10101100.00010000.00111111.11111111 172.16.63.255
5
Network Address 10101100.00010000.01000000.00000000 172.16.64.0
First IP Address 10101100.00010000.01000000.00000001 172.16.64.1
Last IP Address 10101100.00010000.01001111.11111110 172.16.79.254
Broadcast Address 10101100.00010000.01001111.11111110 172.16.79.255
6
Network Address 10101100.00010000.01010000.00000000 172.16.80.0
First IP Address 10101100.00010000.01010000.00000001 172.16.80.1
Last IP Address 10101100.00010000.01011111.11111110 172.16.95.254
Broadcast Address 10101100.00010000.01011111.11111111 172.16.95.255
7
Network Address 10101100.00010000.01100000.00000000 172.16.96.0
First IP Address 10101100.00010000.01100000.00000001 172.16.96.1
Last IP Address 10101100.00010000.01101111.11111110 172.16.111.254
Broadcast Address 10101100.00010000.01101111.11111110 172.16.111.255
8
Network Address 10101100.00010000.01110000.00000000 172.16.112.0
First IP Address 10101100.00010000.01110000.00000001 172.16.112.1
Last IP Address 10101100.00010000.01111111.11111110 172.16.127.254
Broadcast Address 10101100.00010000.01111111.11111111 172.16.127.255
9
Network Address 10101100.00010000.10000000.00000000 172.16.128.0
First IP Address 10101100.00010000.10000000.00000001 172.16.128.1
Last IP Address 10101100.00010000.10001111.11111110 172.16.143.254
Broadcast Address 10101100.00010000.10001111.11111111 172.16.143.255
10
Network Address 10101100.00010000.10010000.00000000 172.16.144.0
First IP Address 10101100.00010000.10010000.00000001 172.16.144.1
Last IP Address 10101100.00010000.10011111.11111110 172.16.159.254
Broadcast Address 10101100.00010000.10011111.11111111 172.16.159.255
11
Network Address 10101100.00010000.10100000.00000000 172.16.160.0
First IP Address 10101100.00010000.10100000.00000001 172.16.160.1
Last IP Address 10101100.00010000.10101111.11111110 172.16.175.254
Broadcast Address 10101100.00010000.10101111.11111111 172.16.175.255
12
Network Address 10101100.00010000.10110000.00000000 172.16.176.0
First IP Address 10101100.00010000.10110000.00000001 172.16.176.1
Last IP Address 10101100.00010000.10111111.11111110 172.16.191.254
Broadcast Address 10101100.00010000.10111111.11111111 172.16.191.255
13 Network Address 10101100.00010000.11000000.00000000 172.16.192.0
First IP Address 10101100.00010000.11000000.00000001 172.16.192.1
Last IP Address 10101100.00010000.11001111.11111110 172.16.207.254
Broadcast Address 10101100.00010000.11001111.11111111 172.16.207.255
14
Network Address 10101100.00010000.11010000.00000000 172.16.208.0
First IP Address 10101100.00010000.11010000.00000001 172.16.208.1
Last IP Address 10101100.00010000.11011111.11111110 172.16.223.254
Broadcast Address 10101100.00010000.11011111.11111111 172.16.223.255
15
Network Address 10101100.00010000.11100000.00000000 172.16.224.0
First IP Address 10101100.00010000.11100000.00000001 172.16.224.1
Last IP Address 10101100.00010000.11101111.11111110 172.16.239.254
Broadcast Address 10101100.00010000.11101111.11111111 172.16.239.255
16
Network Address 10101100.00010000.11110000.00000000 172.16.240.0
First IP Address 10101100.00010000.11110000.00000001 172.16.240.1
Last IP Address 10101100.00010000.11111111.11111110 172.16.255.254
Broadcast Address 10101100.00010000.11111111.11111111 172.16.255.255
The network 172.16.0.0 is divided into sixteen networks, each network has 4096 total IP addresses and 4094 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id). The subnet mask is 255.255.240.0.
Class B Subnetting can be summerized as below.
Subnet Bits
Subnet Mask CIDR Total Subnets
Usable IP Address/Subnet
0 255.255.0.0 /16 1 65534
1 255.255.128.0 /17 2 32766
2 255.255.192.0 /18 4 16382
3 255.255.224.0 /18 8 8190
4 255.255.240.0 /20 16 4094
5 255.255.248.0 /21 32 2046
6 255.255.252.0 /22 64 1022
7 255.255.254.0 /23 128 510
8 255.255.255.0 /24 256 254
9 255.255.255.128 /25 512 126
10 255.255.255.192 /26 1024 62
11 255.255.255.224 /27 2048 30
12 255.255.255.240 /28 4096 14
13 255.255.255.248 /29 8192 6
14 255.255.255.252 /30 16384 2
CLASS A SUBNETTING
Remember, the first octet of a Class A network is used to represent the network and the remaining three octets are used to represent the host. The default format for a Class A IP address is Network.Host.Host.Host.
Let us consider an example of Class A network 10.0.0.0 - 255.0.0.0. The binary representation of the above network and subnet mask is
Component Binary Decimal
Address Part 00001010.00000000.00000000.00000000 10.0.0.0
Subnet Mask 11111111.00000000.00000000.00000000 255.0.0.0
Once again,
If all the bits in the host part are "0", that represents the network id.
If all the bits in the host part are "0" except the last bit, it is the first usable IP address.
If all the bits in the host part are "1" except the last bit, it is the last usable IP address.
If all the bits in the host part are "1", that represents the direct broadcat address.
All the IP addresses between the first and last IP addresses (including the first and last) can be used to configure the devices.
CLASS A - ONE BIT SUBNETTING
If we include one bit from the host part to the network part, the subnet mask is changed into 255.255.128.0 The single bit can have two values in second octet, either 0 or 1.
00001010.0 | 0000000.00000000.00000000 11111111.1 | 0000000.00000000.00000000
That means, we can get two subnets if we do a single bit subnetting. The subnet mask for one bit subnetting is 255.128.0.0.
SN No
Description
Binaries
Decimal
1
Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IP Address 00001010.00000000.00000000.00000001 10.0.0.1
Last IP Address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 100001010.01111111.11111111.11111110 10.127.255.255
2
Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IP Address 00001010.10000000.00000000.00000001 10.128.0.1
Last IP Address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255
The network 10.0.0.0 is divided into two networks, each network has 8388608 total IP addresses and 8388606 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id).
CLASS A - TWO BIT SUBNETTING
If we include two bits from the host part to the network part, the subnet mask is changed into 255.192.0.0. The two bits added to network part can have four possible values in second octet, 00, 01, 10, and 11.
00001010.00 | 000000.00000000.00000000 11111111.11 | 000000.00000000.00000000
That means, we can get four networks if we do a two bit subnetting. The subnet mask for two bit subnetting is 255.192.0.0.
SN No
Description
Binaries
Decimal
1
Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IP Address 00001010.00000000.00000000.00000001 10.0.0.1
Last IP Address 00001010.00111111.11111111.11111110 10.63.255.254
Broadcast Address 00001010.00111111.11111111.11111111 10.63.255.255
2
Network Address 00001010.01000000.00000000.00000000 10.64.0.0
First IP Address 00001010.01000000.00000000.00000001 10.64.0.1
Last IP Address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 00001010.01111111.11111111.11111110 10.127.255.255
3
Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IP Address 00001010.10000000.00000000.00000001 10.128.0.1
Last IP Address 00001010.10111111.11111111.11111110 10.191.255.254
Broadcast Address 00001010.10111111.11111111.11111111 10.191.255.255
4
Network Address 00001010.11000000.00000000.00000000 10.192.0.0
First IP Address 00001010.11000000.00000000.00000001 10.192.0.1
Last IP Address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255
The network 10.0.0.0 is divided into four networks, each network has 4194304 total IP addresses and 4194302 usable IP addresses (two IP addresses are used in each subnet to represent the network id and the broadcast id).
CLASS A - 3 BIT SUBNETTING
If we include three bits from the host part to the network part, the subnet mask is changed into 255.224.0.0 The three bits added to network part can have eight possible values in the second octet and that are 000, 001, 010, and 011, 100, 101, 110 and 111.
00001010.000 | 00000.00000000.00000000 11111111.111 | 00000.00000000.00000000
That means, we can get eight networks if we do a three bit subnetting and the subnet mask will be 255.224.0.0.
SN No
Description
Binaries
Decimal
1
Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IP Address 00001010.00000000.00000000.00000001 10.0.0.1
Last IP Address 00001010.00011111.11111111.11111110 10.31.255.254
Broadcast Address 00001010.00011111.11111111.11111111 10.31.255.255
2
Network Address 00001010.00100000.00000000.00000000 10.32.0.0
First IP Address 00001010.00100000.00000000.00000001 10.32.0.1
Last IP Address 00001010.00111111.11111111.11111110 10.63.255.254
Broadcast Address 00001010.00111111.11111111.11111111 10.63.255.255
3
Network Address 00001010.01000000.00000000.00000000 10.64.0.0
First IP Address 00001010.01000000.00000000.00000001 10.64.0.1
Last IP Address 00001010.01011111.11111111.11111110 10.95.255.254
Broadcast Address 00001010.01011111.11111111.11111111 10.95.255.255
4
Network Address 00001010.01100000.00000000.00000000 10.96.0.0
First IP Address 00001010.01100000.00000000.00000001 10.96.0.1
Last IP Address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 00001010.01111111.11111111.11111111 10.127.255.255
5
Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IP Address 00001010.10000000.00000000.00000001 10.128.0.1
Last IP Address 00001010.10011111.11111111.11111110 10.159.255.254
Broadcast Address 00001010.10011111.11111111.11111111 10.159.255.255
6 Network Address 00001010.10100000.00000000.00000000 10.160.0.0
First IP Address 00001010.10100000.00000000.00000001 10.160.0.1
Last IP Address 00001010.10111111.11111111.11111110 10.191.255.254
Broadcast Address 00001010.10111111.11111111.11111111 10.191.255.255
7
Network Address 00001010.11000000.00000000.00000000 10.192.0.0
First IP Address 00001010.11000000.00000000.00000001 10.192.0.1
Last IP Address 00001010.11011111.11111111.11111110 10.223.255.254
Broadcast Address 00001010.11011111.11111111.11111111 10.223.255.255
8
Network Address 00001010.11100000.00000000.00000000 10.224.0.0
First IP Address 00001010.11100000.00000000.00000001 10.224.0.1
Last IP Address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255
The network 10.0.0.0 is divided into eight networks, each network has 2097152 total IP addresses and 2097150 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id).
CLASS A - 4 BIT SUBNETTING:
If we include four bits from the host part to the network part, the subnet mask is changed to 255.240.0.0.
00001010.0000 | 0000.00000000.00000000 11111111.1111 | 0000.00000000.00000000
The four bits added to network part can have sixteen possible values in second octet and that are 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111.
SN No
Description
Binaries
Decimal
1
Network Address 00001010.00000000.00000000.00000000 10.0.0.0
First IP Address 00001010.00000000.00000000.00000001 10.0.0.1
Last IP Address 00001010.00001111.11111111.11111110 10.15.255.254
Broadcast Address 00001010.00001111.11111111.11111111 10.15.255.255
2
Network Address 00001010.00010000.00000000.00000000 10.16.0.0
First IP Address 00001010.00010000.00000000.00000001 10.16.0.1
Last IP Address 00001010.00011111.11111111.11111110 10.31.255.254
Broadcast Address 00001010.00011111.11111111.11111111 10.31.255.255
3
Network Address 00001010.00100000.00000000.00000000 10.32.0.0
First IP Address 00001010.00100000.00000000.00000001 10.32.0.1
Last IP Address 00001010.00101111.11111111.11111110 10.47.255.254
Broadcast Address 00001010.00101111.11111111.11111111 10.47.255.255
4
Network Address 00001010.00110000.00000000.00000000 10.48.0.0
First IP Address 00001010.00110000.00000000.00000001 10.48.0.1
Last IP Address 00001010.00111111.11111111.11111110 10.63.255.254
Broadcast Address 00001010.00111111.11111111.11111111 10.63.255.255
5
Network Address 00001010.01000000.00000000.00000000 10.64.0.0
First IP Address 00001010.01000000.00000000.00000001 10.64.0.1
Last IP Address 00001010.01001111.11111111.11111110 10.79.255.254
Broadcast Address 00001010.01001111.11111111.11111111 10.79.255.255
6
Network Address 00001010.01010000.00000000.00000000 10.80.0.0
First IP Address 00001010.01010000.00000000.00000001 10.80.0.1
Last IP Address 00001010.01011111.11111111.11111110 10.95.255.254
Broadcast Address 00001010.01011111.11111111.11111110 10.95.255.255
7
Network Address 00001010.01100000.00000000.00000000 10.96.0.0
First IP Address 00001010.01100000.00000000.00000001 10.96.0.1
Last IP Address 00001010.01101111.11111111.11111110 10.111.255.254
Broadcast Address 00001010.01101111.11111111.11111110 10.111.255.255
8 Network Address 00001010.01110000.00000000.00000000 10.112.0.0
First IP Address 00001010.01110000.00000000.00000001 10.112.0.1
Last IP Address 00001010.01111111.11111111.11111110 10.127.255.254
Broadcast Address 00001010.01111111.11111111.11111111 10.127.255.255
9
Network Address 00001010.10000000.00000000.00000000 10.128.0.0
First IP Address 00001010.10000000.00000000.00000001 10.128.0.1
Last IP Address 00001010.10001111.11111111.11111110 10.143.255.254
Broadcast Address 00001010.10001111.11111111.11111111 10.143.255.255
10
Network Address 00001010.10010000.00000000.00000000 10.144.0.0
First IP Address 00001010.10010000.00000000.00000001 10.144.0.1
Last IP Address 00001010.10011111.11111111.11111110 10.159.255.254
Broadcast Address 00001010.10011111.11111111.11111111 10.159.255.255
11
Network Address 00001010.10100000.00000000.00000000 10.160.0.0
First IP Address 00001010.10100000.00000000.00000001 10.160.0.1
Last IP Address 00001010.10101111.11111111.11111110 10.175.255.254
Broadcast Address 00001010.10101111.11111111.11111111 10.175.255.255
12
Network Address 00001010.10110000.00000000.00000000 10.176.0.0
First IP Address 00001010.10110000.00000000.00000001 10.176.0.1
Last IP Address 00001010.10111111.11111111.11111110 10.191.255.254
Broadcast Address 00001010.10111111.11111111.11111111 10.191.255.255
13
Network Address 00001010.11000000.00000000.00000000 10.192.0.0
First IP Address 00001010.11000000.00000000.00000001 10.192.0.1
Last IP Address 00001010.11001111.11111111.11111110 10.207.255.254
Broadcast Address 00001010.11001111.11111111.11111111 10.207.255.255
14
Network Address 00001010.11010000.00000000.00000000 10.208.0.0
First IP Address 00001010.11010000.00000000.00000001 10.208.0.1
Last IP Address 00001010.11011111.11111111.11111110 10.223.255.254
Broadcast Address 00001010.11011111.11111111.11111111 10.223.255.255
15
Network Address 00001010.11100000.00000000.00000000 10.224.0.0
First IP Address 00001010.11100000.00000000.00000001 10.224.0.1
Last IP Address 00001010.11101111.11111111.11111110 10.239.255.254
Broadcast Address 00001010.11101111.11111111.11111111 10.239.255.255
16
Network Address 00001010.11110000.00000000.00000000 10.240.0.0
First IP Address 00001010.11110000.00000000.00000001 10.240.0.1
Last IP Address 00001010.11111111.11111111.11111110 10.255.255.254
Broadcast Address 00001010.11111111.11111111.11111111 10.255.255.255
The network 10.0.0.0 is divided into sixteen networks, each network has 1048576 total IP addresses and 1048574 usable IP addresses (two IP addresses are used in each subnet to represent the netwok id and the broadcast id).
From the above examples, you can clearly understand how to subnet a Class A network.
Class A Subnetting can be summerized as below.
Subnet Bits
Subnet Mask CIDR Total Subnets
Usable IP Address/Subnet
0 255.0.0.0 /8 1 16777214
1 255.128.0.0 /9 2 8388606
2 255.192.0.0 /10 4 4194302
3 255.224.0.0 /11 8 2097150
4 255.240.0.0 /12 16 1048574
5 255.248.0.0 /13 32 524286
6 255.252.0.0 /14 64 262142
7 255.254.0.0 /15 128 131070
8 255.255.0.0 /16 256 65534
9 255.255.128.0 /17 512 32766
10 255.255.192.0 /18 1024 16382
11 255.255.224.0 /19 2048 8190
12 255.255.240.0 /20 4096 4094
13 255.255.248.0 /21 8192 2046
14 255.255.252.0 /22 16384 1022
15 255.255.254.0 /23 32768 510
16 255.255.255.0 /24 65536 254
17 255.255.255.128 /25 131072 126
18 255.255.255.192 /26 262144 62
19 255.255.255.224 /27 524288 30
20 255.255.255.240 /28 1048576 14
21 255.255.255.248 /29 2097152 6
22 255.255.255.252 /30 4194304 2
A PRACTICAL SCENARIO FOR YOU:
Here is another, more detailed, example. Say you are assigned a Class C network number of 200.133.175.0. You want to utilize this network across multiple small groups within an organization. You can do this by subnetting that network with a subnet address.
We will break this network into 14 subnets of 14 nodes each. This will limit us to 196 nodes on the network instead of the 254 we would have without subnetting, but gives us the advantages of traffic isolation and security. To accomplish this, we need to use a subnet mask 4 bits long. Recall that the default Class C subnet mask is:
255.255.255.0 (11111111.11111111.11111111.00000000 binary)
Extending this by 4 bits yields a mask of 255.255.255.240 (11111111.11111111.11111111.11110000 binary)
This gives us 16 possible network numbers, 2 of which cannot be used:
Subnet bits Network Number Node Addresses Broadcast Address
0000 200.133.175.0 Reserved None
0001 200.133.175.16 .17 thru .30 200.133.175.31
0010 200.133.175.32 .33 thru .46 200.133.175.47
0011 200.133.175.48 .49 thru .62 200.133.175.63
0100 200.133.175.64 .65 thru .78 200.133.175.79
0101 200.133.175.80 .81 thru .94 200.133.175.95
0110 200.133.175.96 .97 thru .110 200.133.175.111
0111 200.133.175.112 .113 thru .126 200.133.175.127
1000 200.133.175.128 .129 thru .142 200.133.175.143
1001 200.133.175.144 .145 thru .158 200.133.175.159
1010 200.133.175.160 .161 thru .174 200.133.175.175
1011 200.133.175.176 .177 thru .190 200.133.175.191
1100 200.133.175.192 .193 thru .206 200.133.175.207
1101 200.133.175.208 .209 thru .222 200.133.175.223
1110 200.133.175.224 .225 thru .238 200.133.175.239
1111 200.133.175.240 Reserved None
VARIABLE LENGTH SUBNET MASKING (VLSM) :
Variable Length Subnet Masking (VLSM) is a way of further subnetting a subnet. Using Variable Length Subnet Masking (VLSM) we can allocate IP addresses to the subnets by the exact need. Variable Length Subnet Masking (VLSM) allows us to use more than one subnet mask within the same network address space. If we recollect from the previous lessons, we can divide a network only into subnets with equal number of IP addresses. Variable Length Subnet Masking (VLSM) allows to create subnets from a single network with unequal number of IP addresses.
Example: We want to divide 192.168.10.0, which is a Class C network, into four networks, each with unequal number of IP address requirements as shown below.
Subnet A: 126 IP Addresses. Subnet B: 62 IP Addresses. Subnet C: 30 IP Addresses. Subnet D : 30 IP Addresses.
This type of division is not possible as described in previous lessons, since it divide the network equally, but is possible with Variable Length Subnet Masking (VLSM).
Original Network (Network to be sub-netted) – 192.168.10.0/24
Variable Length Subnet Masking (VLSM) - First Division
Divide the two networks equally with 128 IP Addresses (126 usable IP addresses) in each network using 255.255.255.128 subnet mask (192.168.10.0/25).
We will get two subnets each with 128 IP Addresses (126 usable IP addresses).
1) 192.168.10.0/25, which can be represented in binaries as below.
11000000.10101000.00001010.0 | 0000000 11111111.11111111.11111111.1 | 0000000
2) 192.168.10.128/25, which can be represented in binaries as below.
11000000.10101000.00001010.1 | 0000000 11111111.11111111.11111111.1 | 0000000
Variable Length Subnet Masking (VLSM)- Second Division
Divide second subnet (192.168.10.128/25) we got from the first division again into two Networks, each with 64 IP Addresses (62 usable IP Addresses) using 255.255.255.192 subnet mask.
We will get two subnets each with 64 IP Addresses (62 usable IP Addresses).
1) 192.168.10.128/26, which can be represented in binaries as below.
11000000.10101000.00001010.1 | 0 | 000000 11111111.11111111.11111111.1 | 1 | 000000
2) 192.168.10.192/26
11000000.10101000.00001010.1 | 1 | 000000 11111111.11111111.11111111.1 | 1 | 000000
Variable Length Subnet Masking (VLSM) - Third Division
Divide 192.168.10.192/26 Network again into two Networks, each with 32 IP Addresses (30 usable IP addresses) using 255.255.255.224 subnet mask
We will get two subnets each with 32 IP Addresses (30 usable IP addresses).
1) 192.168.10.192/27, which can be represented in binaries as below.
11000000.10101000.00001010.11 | 0 | 00000 11111111.11111111.11111111.11 | 1 | 00000
2) 192.168.10.224/27, which can be represented in binaries as below.
11000000.10101000.00001010.11 | 1 | 00000 11111111.11111111.11111111.11 | 1 | 00000
Now we have split the 192.168.10.0/24 network into four subnets using Variable Length Subnet Masking (VLSM), with unequal number of IP addresses as shown below. Also note that when you divide a network using Variable Length Subnet Masking (VLSM), the subnet masks are also different.
1) 192.168.10.0 - 255.255.255.128 (126 (128-2) usable IP Addresses) 2) 192.168.10.128 - 255.255.255.192 (62 (64-2) usable IP Addresses) 3) 192.168.10.192 - 255.255.255.224 (30 (32-2) usable IP Addresses) 4) 192.168.10.224 - 255.255.255.224 (30 (32-2) usable IP Addresses)
SUPERNETTING:
Supernetting is the method for combing two or more contiguous network address spaces to simulate a single, larger, address space. You may remember, in Subnetting we are adding the bits from the host part to the network part. But in Supernetting we do the reverse. Here in supernetting we add bits from the network part to the host part. To supernet two contiguous networks is simple. Just convert the networks in to binaries, compare the bits of the two networks. Till where you have the similiar bit pattern, use a subnet mask bit of "1", and after that "0". Use the altered subnet mask for two networks. That’s it!
For example, you may want to supernet the networks 192.168.10.0 and 192.168.11.0 to make a single, large network. Following two lines are the conversions of the above network addresses to binaries and the last line is the new subnet mask.
11000000.10101000.0000101 | 0.00000000
11000000.10101000.0000101 | 1.00000000
11111111.11111111.1111111 | 0.00000000
The changed subnet mask is 255.255.254.0 can be used to supernet 192.168.10.0 and 192.168.11.0. The concept of supernetting is used in routing protocols for "route summarization".
