How to setup a network with multiple subnets

This article explains the different ways by which you can setup a network with multiple subnets. We make an assumption that every subnet has 10 systems on it.

The two subnets which we would be using on the network would be 192.168.1.0/24 and 192.168.2.0/24. The IP address range 192.168.1.1 -192.168.1.10 is used for the 1st subnet and the IP address range 192.168.2.1-192.168.2.10 would be used for the second subnet.

Which switch should you buy

Switches form the core of the network setup. In this example, we make an assumption that there are in total 20 users on the network. To accommodate 20 users, a 24 port switch would be required. In case your network has more number of users, then purchase the switch accordingly. For example, if the number of users on the network is greater than 30, a 48 port switch would be recommended.

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If you do not want to logically segregate your subnets, then an unmanaged switch would suffice. But if you want to segregate , then a managed switch would be recommended. A managed switch would help control broadcasts in a more efficient manner but it would be more expensive than an unmanaged switch.




Two different topologies are explained for setting up of the network.

Topology 1 – Network Setup with multiple subnets with unmanaged switch

There are 20 users on the network. To accommodate 20 users, a 24 port switch would be required. In this topology, an unmanaged switch is used. All the users on the network which include subnet 1 and subnet 2 would be connected to the respective ports on the switch. The users on subnet 1 and subnet 2 would belong to one large broadcast domain.

Topology 2 – Network Setup with multiple subnets with managed switch

In this topology, a managed switch would be used. A managed switch would give you the provision to setup multiple broadcast domains on a single network. The broadcast domains are setup using vlans. In this example, we create two vlans on the switch. The ports on the switch are configured for respective vlans.

Each subnet is associated with a VLAN. Create VLAN 2 and VLAN 3 on the switch. Configure ports 1-10 as member of VLAN 2 and ports 11-21 as member of VLAN 3. Connect the respective systems belonging to subnet 1 and subnet 2 to the respective ports.

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How to communicate between the subnets

In topology 1 and 2, you would need to use a router for communicating between the subnets. In topology 1, a router which has atleast two LAN interfaces should be used. This is to create two physical networks. In topology 2, the router should support one LAN interface which has support for 802.1Q. This is for enabling communication between VLANs.

The step by step procedure to integrate a router in topology 1 and topology 2 is explained below.

Topology 1 – Router integration

Connect two switch ports to the LAN interfaces of the router. Configure the 1st LAN interface of the router with IP address as 192.168.1.1 and the second LAN interface of the router with IP address as 192.168.2.1. This would be the default gateway IP address of the systems connected to the switches. All devices belonging to subnet 1 would have the default gateway as 192.168.1.1 and that on subnet 2 would have the default gateway as 192.168.2.1. If the configuration is successful, you should be able to ping devices on the network.

Topology 2 – Router integration

Configure one of the switch ports as trunk port. A trunk port is a port capable of carrying multiple VLAN traffic. This port should be connected to the port of the router. Configure multiple sub interfaces of the router on the LAN port of the router and associate the IP address 192.168.1.1 with VLAN 2 and the IP address 192.168.2.1 with VLAN 3. All devices belonging to subnet 1 would have the default gateway as 192.168.1.1 and that on subnet 2 would have the default gateway as 192.168.2.1. If the configuration is successful, you should be able to ping devices on the network.

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Recommendation & FAQs

Which topology should you use for communication between subnets

If you are using an unmanaged switch with a basic router, the cost would be significantly lower. This topology is recommended if you have less number of devices on the network where broadcasting on one large subnet would not be an issue.

If you are using a managed switch with a router which supports 802.1Q, then the cost would be significantly higher. This topology is recommended if you want to segregate the network into smaller logical networks and control broadcasts efficiently.

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If manageability is a priority , then topology 2 would be recommended.

Which topology should you use if communication between subnets is not required

Using an unmanageable switch would significantly lower your price. This is recommended if you dont have a large network and manageability is not your priority. If its a large network and you need better manageability , then using a managed switch would be a better option.

What should I do if the users are placed on different floors on a building

You would need to buy multiple switches. For example, if there are 20 users each on different floors, purchase 3 units of 24 port switches and connect each of the switches to each other using appropriate cables.

What should I do if internet has to be integrated on the network

The internet connection has to be setup on the router. The internet has to be shared using NAT technology on the router. This would ensure that all users on the network are able to access the internet available on the router.

What additional parameters should be configured on the systems to access internet

The DNS IP address value should be configured on the TCP/IP adapter of each system on the network. The DNS IP address value would be the IP address of the router. For subnet 1 , it would be 192.168.1.1 and for subnet 2 , it would be 192.168.2.1.




Which vendors manufacture these switches

Almost all networking vendors manufacture managed and unmanaged switches. Some of the vendors include Cisco, HP, NETGEAR , TPLINK etc.

Where can I buy these switches

You can check it out on Amazon here. Check out switches here

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