Can wifi and lan work together on your laptop

Yes. wifi and lan can indeed work together. This article explains how wifi and lan can work together and multiple scenarios where this can be implemented and how the communication works in multiple scenarios. Common FAQ’s related to this article is also answered.

Lets take a laptop which has an inbuilt wifi card and a LAN interface card. Both the wifi card and LAN interface card are configured with an IP address. The IP addresses are unique for each of the interfaces.

Scenarios where you can be connected to Wifi and LAN together

Scenario 1 : Wifi and LAN connected to the same router

In this scenario, the laptop is connected to the same router. The wifi on the laptop is connected to the wireless network on the router and the LAN is connected to the interface of the switch which is inbuilt on the router.

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Both the interfaces receive IP address from the DHCP server on the router. This implies that the laptop now has two interfaces, which are connected on the same network and the IP addresses also belongs to the same network range.

How does the communication work

Assume that you access a website from the laptop. During this time, a connection is initiated from one of the interfaces (Wifi or LAN). Which interface do you think would be selected by the laptop for establishing the connection ?

This is where the concept of routing tables is used by the operating system of the laptop. When there are two paths to the same network, the path with the lowest metric value would be selected. This is explained below:

The network here refers to the internet network and the path refers to the interfaces (Wifi and Lan).The interface associated with the lowest metric value on the laptop would be selected to initiate the connection. This could either be the LAN or Wifi interface.

Scenario 2 : Wifi connected to router and LAN to a different network

In this scenario, the wifi card on the laptop is connected to the wireless router on the network and the LAN interface is connected to a switch on a different network. This is a typical scenario where your laptop is connected to different networks using multiple network cards.

A common scenario is where you are using the LAN card, which is typically faster than your wifi card to access bandwidth intensive in house applications or for gaming.

How does the communication work

In this scenario, there are two networks. The routing table in this case would have paths to two different networks which is the wifi network and the network on the switch. To access the wifi network, the interface connected to the wifi router would be selected and to access the other network, the LAN interface would be selected.

FAQ

1. In scenario 1, what would happen if the wifi card connected to the router fails and this was the connection used by my laptop for accessing the internet?

The current connections would be dropped. The next time you try to access the internet or a website, the LAN card would be selected by the operating system, since the wifi card would not be available in the routing table because faulty or disabled adapters do not show up in the routing table.

2. Which adapter would be selected by the routing table as a default?

The adapter corresponding to the lowest metric value in the routing table would be selected.

3. Does routing table assign the metric value to common paths based on the speed of the interface ?

Not necessary. This would depend on the operating system and the technique it uses for selection of the interface.

4. If I use an additional wifi adapter , can I use three adapters to connect to three different networks ?

Yes. This is absolutely possible.

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5. How do I setup a network which has a wifi card connecting to the wireless router and LAN card connecting to a different network which has a server ?

A switch has to be purchased for setting up this network. Identify the number of devices which would be connecting to the network including the server. Based on the number, the switches can be selected.

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Connect the LAN interface of the laptop to the switch and configure it with an IP address which is different from the wifi network.

6. I want my desktop to connect to wifi and use LAN for another network. What should I do ?

Purchase a PCI or a USB card and connect it to the desktop. Connect the card to the wifi router and the LAN card to the other network.

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7. I want to force my laptop to take the LAN interface in scenario 1. What should I do ?

The metric value of the interface has to be set at a lower value than the wifi card. This has to be done manually through the command line of the operating system.

8. In scenario 1, will the internet speed become faster because both Wifi and LAN is used ?

No. Only 1 card is used at a time. The cards are not aggregated. So the internet speed will be the same irrespective of whether you use 1 card or multiple cards.

9. Is there any benefit of using Wifi and LAN together ?

In scenario 1, one of the connections can be used as a backup. In scenario 2, two networks can be setup. But it should be noted that there would not be any performance improvement since only one network connection is used at a time.

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