How to setup multiple networks with one router

This article explains 3 different options by which you can setup multiple networks with one router. As there are two different networks, two IP networks are required. We assign this as 192.168.1.0/24 and 192.168.2.0/24. It is assumed that there are 10 users each on both networks.

The IP address of the router interfaces associated with both networks are configured with the IP address 192.168.1.1/24 and 192.168.2.1/24. The systems on network 1 (192.168.1.0/24) are configured with the IP address range 192.168.1.2-192.168.1.11 where 192.168.1.1 is reserved for the router.

The systems on network 2 (192.168.2.0/24) are configured with the IP address range 192.168.2.2-192.168.2.11 where 192.168.2.1 is reserved for the router.

The default gateway for systems on network 1 would be 192.168.1.1 and that of network 2 would be 192.168.2.1. These parameters would be the same for all the options explained below.

How to connect two different networks with one router and a single switch – Option 1

In this option, we use a single switch to setup the network. As there are 20 users in total and additional two ports for connecting the interfaces of the router associated with each of the networks, a 24 port switch would suffice. Note that, in case the number of users are greater, then a 48 port switch would be required.

The below diagram shows the setup. All systems including the router interfaces are connected to ports on the switch.

Advantages & Disadvantages

In this setup, all the users on network 1 and network 2 are connected to a single switch. This creates one large broadcast domain. The broadcast traffic from one network would reach all users irrespective of whether they belong to network 1 or network 2, since switches send broadcast traffic to all ports on it. This could create performance issues on the network in general.

From a budget perspective, it would be very economical since you are purchasing only a single switch to accommodate all users on the network.

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How to connect two different networks with one router and multiple switches – Option 2

In this option, we use multiple switches to setup the network. Each switch would connect to the individual port on the router which would provide better segregation of the network. Each network has 10 users and an additional port for connecting the router interface.

To accommodate, you would need to purchase 2 numbers of 12 port switches. If the number of users are more, 24 port switches would be required.

Advantages & Disadvantages

In this setup, users on network 1 and network 2 are connected to two different switches. This creates two separate broadcast domains , one for each network. The broadcast traffic from one network would never reach the other network since routers do not forward broadcast traffic.

Performance issues would be significantly lower as compared with option 1 since the networks are segregated.

From a budget perspective, it could be more expensive since you are purchasing two switches instead of 1.

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How to connect two different networks with one router and single switch with VLAN – Option 3

In this setup, a switch which supports VLAN is used.The router should also support VLAN. The switch is configured for two VLANs for both the networks.

VLAN 2 is associated with network 1 and VLAN 3 is associated with network 2. The ports on the switch are configured as members of VLAN 2 and VLAN 3.

The users belonging to network 1 are connected to ports on the switch configured as VLAN 2 and users on network 2 are connected to ports on the switch configured as VLAN 3.

One interface of the router is connected to the switch. This port on the switch is configured as a trunk port to carry VLAN traffic.

The interface on the router is divided into two virtual sub interfaces, which is then configured with the multiple IP addresses. In option 1 and option 2, the IP addresses were configured using two physical interfaces on the router.

Advantages & Disadvantages

In this setup, users on the network 1 and network 2 are connected using a single switch. But it should be observed that the networks are segregated efficiently using VLANs. VLANs create multiple broadcast domains. So, broadcast traffic is restricted within the networks and this would eliminate any performance issues.

Also note that, from a management perspective, this could be the best option since VLANs are supported by the switches. This would not be available on the other two options.

From a budget perspective, this would be the most expensive option compared with option 1 and option 2 , since you need to purchase a switch and a router which support VLANs.

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Solution Recommendation

If performance is your utmost priority and budget is not a constraint, then option 3 would be the best choice. If budget is a constraint but you cannot have any performance issues, then option 2 would be the best choice. If budget is a constraint and minor performance issues are not a problem, then option 1 would be the best choice.

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