Set up the LAN by Dividing the Subnet

This updated guide examines Set up the LAN by Dividing the Subnet and organizes the essential facts, background, and practical takeaways in clear American English.

You need to build an intranet (LAN) for an office, a small and medium-sized company with about 7 to 8 rooms, each with 30 machines. The problem is how to be effective, secure the network system, prevent possible risks, but also can save network resources.

A LAN model.

One of the effective construction methods is planning IP addresses by dividing subnet . With this option, you will only provide a sufficient number of IP addresses for computers to use, split into multiple subnets, prevent broadcast events and if there is a problem, only locally subnet branch. An IP address consists of 4 octets, each octet is 1 byte containing 8 bits, a total of 32 bits. The IP address will be identified in class A, B or C through the subnet mask address. With the above problem, we will use the C class. You need 30 machines, we see 25 = 32, minus 2 first and last addresses are network addresses and broadcast addresses of the network branch, you will be left 30 addresses. Thus, 1 octave has 8 bits, we will take 28 - 23 = 25, meaning you will borrow 3 more bits to divide the subnet for your network. How to divide by a procedure is as follows:

Class C has a subnet mask of 255.255.255.0 or even written as / 24. An 8-bit octet, you borrow 3 bits, the number of borrowed bits will turn as many as 1, the remaining number of bits will remain at 0.

128 64 32 16 8 4 2 1 1 1 1 0 0 0 0

0

You get 3 bits of value 1 combined: 128 + 64 + 32 = 224. Similarly, if you borrow 4 bits, the subnet mask will be 240. From there, to make it easy to remember, people on the network set a table to look up.

1 128 -128 2 192 -64 3 224 -32 4240-16 5 248 +8 6 252 +4 7 254 +2 8 255 +1

You only need to remember the value in the 4th bit to borrow will have the corresponding subnet mask value of 240, from which you add and subtract as above table to find the subnet mask of the other bits. Returning to the above problem, using the C network layer and borrowing an additional 3 bits (24 + 3 = 27), you will have a 255.255.255.224 subnet mask, and each subnet branch will be divided accordingly as follows:

• 0. 192.168.1.0/27

• 1: 192.168.1.32/27

• 2: 192.168.1.64/27

• 3: 192.168.1.96/27

• 4: 192.168.1.128/27

• 5: 192.168.1.160/27

• 6: 192.168.1.192/27

• 7: 192.168.1.224/27

• 8: 192.168.1.254/27

Here, you should note in the 8th order number, value 224 + 32 = 256, but because C class has only 254 IP addresses, address 255 is broadcast address, so the network here is 192.168.1.254 , and room 8 you can set the IP address from 192.168.1.225/27 - 192.168.1.253/27 . Similarly, you set room number 1 to the IP address range: 192.168.1.1/27 - 192.168.1.30/2 7, which can use the address 192.168.1.1 as the default address for this room number 1. 2. Application of network system construction

You have completed the subnet split, and will now apply to the local network. Now the rooms are a sub-branch, completely separate. You cannot sit in room number 1 to transfer data, access or use ICMP protocol as ping command to another machine in room 2.

In order for the rooms to connect to the internet, you need to have a computer as a router function. This router will help machines in each local network connect to the ADSL modem and access the internet. If you use a Cisco device like Router 2800, subnet sharing in the router is called Inter Vlan technique.

Depending on the security policy of the company or agency, you can build more firewalls, access lists and mechanisms Nat inside or outside to access the workstations outside the internet, outside the remote internet in. intranet.