Monday, 1 June 2026

IP (internet protocol) address concept in networking

Internet Protocol (IP) address:
An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods(192.168.1.1). Each decimal number represents eight bits of binary data, and therefore can have a decimal value between 0 and 255.

Subnet Mask:
A subnet mask is used to divide an IP address  into two parts.One part is identifes the the host (computer) , the other part identifies the network which belongs.


The first part of an IP address is used as a network address, the last part as host address.
If you take an example 192.168.1.132 and divide it into these two parts you gets the following

192.168.1.0   Network Address
 0.0.0.132      Host Address


For this example  using 255.255.255.0 subnet mask

When a packet arrives on the 192.168.1.0 subnet and it has a designation address of 192.168.1.132 , computer will receive it from the network and process it.


This means that you can use the address 192.168.1.1 to 192.168.1.254 for your computers  to connect in the network.



This means that you can use the address 192.168.1.1 to 192.168.1.254 for your computers  to connect in the network.




The number after the slash represents the number of consecutive 1's in the subnet mask.
For example 192.168.1.0/24 is equal to the network   192.168.1.0 with  255.255.255.0   sub net mask.


Network address:  192.168.1.0/24      
First computer IP address: 192.168.1.3                                                           Second computer IP address: 192.168.1.4
Third computer IP address: 192.168.1.5                          
Subnet mask: 255.255.255.0
Gate way : 192.168.1.2 (Router IP address) 


If you convert 255.255.255.0 to binary , you end up with 24 consecutive 1 's

11111111.11111111.11111111.00000000

IP                                         subnet mask
192.168.1.0/24              255.255.255.0                  
   
192.168.1.0 to 192.168.1.255     Total - 256 host address  


Adress:
192.168.1.0
11000000.10101000.00000001.00000000
Netmask:
255.255.255.0
11111111.11111111.11111111.00000000
Wildcard:
0.0.0.255
00000000.00000000.00000000.11111111
Network Address:
192.168.1.0 / 24
11000000.10101000.00000001.00000000
Broadcast Address:
192.168.1.255
11000000.10101000.00000001.11111111
First host:
192.168.1.1
11000000.10101000.00000001.00000001
Last host:
.192.168.1.254
11000000.10101000.00000001.11111110

ROUTER IP CONFIGURATION :



DHCP

Short for Dynamic Host Configuration Protocol, a protocol for assigning dynamic IP addresses to devices on a network.

IP address conflict:
If you defined a static IP address for a network device, duplicate IP address conflicts may occur on a DHCP network

Network Addressing


IP addresses are broken into 4 octets (IPv4) separated by dots called dotted decimal notation. An octet is a byte consisting of 8 bits. The IPv4 addresses are in the following form:
192.168.1.1
There are two parts of an IP address:
  • Network ID
  • Host ID
The addressing scheme for class A through C networks is shown below.

Network Type
Address Range
Normal Netmask
Comments
Class A
001.x.x.x to 126.x.x.x
255.0.0.0
For very large networks
Class B
128.1.x.x to 191.254.x.x
255.255.0.0
For medium size networks
Class C
192.0.1.x to 223.255.254.x
255.255.255.0
For small networks

There are some network addresses reserved for private use by the Internet Assigned Numbers Authority (IANA).
There are three sets of addresses reserved. These address are shown below:
  • 10.x.x.x
  • 172.16.x.x - 172.31.x.x
  • 192.168.x.x
Other reserved or commonly used addresses:
  • 127.0.0.1 - The loopback interface address.
  • 0.0.0.0 - This is reserved for hosts that don't know their address and use BOOTP or DHCP protocols to determine their addresses.
  • 255 - The value of 255 is never used as an address for any part of the IP address. It is reserved for 
  • broadcast addressing.

To further illustrate, a few examples of valid and invalid addresses are listed below:
  1. Valid addresses:
·         10.1.0.1 through 10.1.0.254
·         10.0.0.1 through 10.0.0.254
·         10.0.1.1 through 10.0.1.254
·         192.168.1.1 trough 192.168.1.254
  1. Invalid addresses:
·         10.1.0.0 - Host IP can't be 0
·         10.1.0.255 - Host IP can't be 255.
·         10.123.255.4         - No network or subnet can have a value of 255.
·         0.12.16.89 - No Class A network can have an address of 0.
·         255.9.56.45 - No network address can be 255.
·         10.34.255.1 - No network address can be 255.
Network/Netmask specification
Sometimes you may see a network interface card (NIC) IP address specified in the following manner:
192.168.1.1/24
The first part indicates the IP address of the NIC which is "192.168.1.1" in this case. The second part "/24" indicates the netmask value meaning in this case that the first 24 bits of the netmask are set. This makes the netmask value 255.255.255.0. If the last part of the line above were "/16", the netmask would be 255.255.0.0.

Guide to sub-class C blocks
Addresses
Hosts
Netmask
Amount of a Class C
/30
4
2
255.255.255.252
1/64
/29
8
6
255.255.255.248
1/32
/28
16
14
255.255.255.240
1/16
/27
32
30
255.255.255.224
1/8
/26
64
62
255.255.255.192
1/4
/25
128
126
255.255.255.128
1/2
/24
256
254
255.255.255.0
1
/23
512
510
255.255.254.0
2
/22
1024
1022
255.255.252.0
4
/21
2048
2046
255.255.248.0
8
/20
4096
4094
255.255.240.0
16
/19
8192
8190
255.255.224.0
32
/18
16384
16382
255.255.192.0
64
/17
32768
32766
255.255.128.0
128
/16
65536
65534
255.255.0.0
256



/24 -- 1 Subnets -- 256 Hosts ; only one Subnet

Network #
IP Range
Broadcast
.0
.1-.254
.255




/25 -- 2 Subnets -- 126 Hosts/Subnet
Network #
IP Range
Broadcast
.0
.1-.126
.127
.128
.129-.254
.255



/26 -- 4 Subnets -- 62 Hosts/Subnet
Network #
IP Range
Broadcast
.0
.1-.62
.63
.64
.65-.126
.127
.128
.129-.190
.191
.192
.193-.254
.255


/27 -- 8 Subnets -- 30 Hosts/Subnet
Network #
IP Range
Broadcast
.0
.1-.30
.31
.32
.33-.62
.63
.64
.65-.94
.95
.96
.97-.126
.127
.128
.129-.158
.159
.160
.161-.190
.191
.192
.193-.222
.223
.224
.225-.254
.255

/28 -- 16 Subnets -- 14 Hosts/Subnet
Network #
IP Range
Broadcast
.0
.1-.14
.15
.16
.17-.30
.31
.32
.33-.46
.47
.48
.49-.62
.63
.64
.65-.78
.79
.80
.81-.94
.95
.96
.97-.110
.111
.112
.113-.126
.127
.128
.129-.142
.143
.144
.145-.158
.159
.160
.161-.174
.175
.176
.177-.190
.191
.192
.193-.206
.207
.208
.209-.222
.223
.224
.225-.238
.239
.240
.241-.254
.255

/29 -- 32 Subnets -- 6 Hosts/Subnet
Network #
IP Range
Broadcast
.0
.1-.6
.7
.8
.9-.14
.15
.16
.17-.22
.23
.24
.25-.30
.31
.32
.33-.38
.39
.40
.41-.46
.47
.48
.49-.54
.55
.56
.57-.62
.63
.64
.65-.70
.71
.72
.73-.78
.79
.80
.81-.86
.87
.88
.89-.94
.95
.96
.97-.102
.103
.104
.105-.110
.111
.112
.113-.118
.119
.120
.121-.126
.127
.128
.129-.134
.135
.136
.137-.142
.143
.144
.145-.150
.151
.152
.153-.158
.159
.160
.161-.166
.167
.168
.169-.174
.175
.176
.177-.182
.183
.184
.185-.190
.191
.192
.193-.198
.199
.200
.201-.206
.207
.208
.209-.214
.215
.216
.217-.222
.223
.224
.225-.230
.231
.232
.233-.238
.239
.240
.241-.246
.247
.248
.249-.254
.255


/30 -- 64 Subnets -- 2 Hosts/Subnet


Network #
IP Range
Broadcast
.0
.1-.2
.3
.4
.5-.6
.7
.8
.9-.10
.11
.12
.13-.14
.15
.16
.17-.18
.19
.20
.21-.22
.23
.24
.25-.26
.27
.28
.29-.30
.31
.32
.33-.34
.35
.36
.37-.38
.39
.40
.41-.42
.43
.44
.45-.46
.47
.48
.49-.50
.51
.52
.53-.54
.55
.56
.57-.58
.59
.60
.61-.62
.63
.64
.65-.66
.67
.68
.69-.70
.71
.72
.73-.74
.75
.76
.77-.78
.79
.80
.81-.82
.83
.84
.85-.86
.87
.88
.89-.90
.91
.92
.93-.94
.95
.96
.97-.98
.99
.100
.101-.102
.103
.104
.105-.106
.107
.108
.109-.110
.111
.112
.113-.114
.115
.116
.117-.118
.119
.120
.121-.122
.123
.124
.125-.126
.127
.128
.129-.130
.131
.132
.133-.134
.135
.136
.137-.138
.139
.140
.141-.142
.143
.144
.145-.146
.147
.148
.149-.150
.151
.152
.153-.154
.155
.156
.157-.158
.159
.160
.161-.162
.163
.164
.165-.166
.167
.168
.169-.170
.171
.172
.173-.174
.175
.176
.177-.178
.179
.180
.181-.182
.183
.184
.185-.186
.187
.188
.189-.190
.191
.192
.193-.194
.195
.196
.197-.198
.199
.200
.201-.202
.203
.204
.205-.206
.207
.208
.209-.210
.211
.212
.213-.214
.215
.216
.217-.218
.219
.220
.221-.222
.223
.224
.225-.226
.227
.228
.229-.230
.231
.232
.233-.234
.235
.236
.237-.238
.239
.240
.241-.242
.243
.244
.245-.246
.247
.248
.249-.250
.251
.252
.253-.254
.255





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