Dual WAN/Internet Router – Load-balance or Failover using two Internet connections


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Image credit: Al Wilson. This picture is published under this creative commons license.

What is a Dual WAN/Internet router?

There are situations when our Internet capacity is not sufficient or our Internet connection is unstable. If you need access to the net continuously, you might consider getting two Internet lines.

But, most of the routers/modems allow you to connect only one WAN/Internet connection. If you need to connect two Internet lines, you need to buy two routers. You need to connect computers individually to each of the routers. Or, if you connect both routers and all the computers to a single switch, you have no control over which packet is sent to which router.

As you can see, this will create a lot of confusion. If you plan to have two Internet lines/connections, it is better to go with a single router that supports two Internet lines/connections.

These routers not only allow you to connect two WAN/Internet lines, but they allow you to load-balance or fail-over between them.

What is load-balancing?

When you have one Internet connection, the data packets are sent through a single line. So, there is no confusion. But when you have two Internet connections, who decides which packet should go via which line? Simple – No one! The packets are sent through one of these connections quite arbitrarily. This not only creates confusion but it also has the potential to choke one line while the other is relatively free.

Load balancing essentially splits the data packets (Internet traffic) between the two lines equally so that both the Internet connections have almost the same load. It uses simple algorithms like round-robin to determine which packet should be sent to which line. Load balancing prevents one Internet connection being over-used while the other is relatively free. So, both the connections are equally utilized. Do check if a router supports load-balancing with Internet connections from a single service provider or multiple service providers, if you decide to buy one.

What is fail-over?

When you have one Internet connection and it fails to work (or is unstable), it becomes difficult for everyone who are dependent on that Internet line for their work. Bigger companies have Internet Leased Lines and ILL’s come with a certain minimum uptime guarantee. So, the Internet down-time is less, for bigger companies. But smaller companies may not be able to afford Internet Leased Lines. Still, they need a reliable/non-stop Internet connection over broadband to work efficiently.

So, smaller companies can buy two broadband lines (from different service providers) and connect them both to the same router, that supports dual Internet/WAN connections. One of these connections can be made primary and will be active (normally used for Internet connectivity). The other is generally passive and it becomes active only when the primary Internet line fails.

The fail-over (or switch-over) to the secondary Internet line generally happens automatically, without user intervention. Normally, it takes a short time for the fail-over to happen once the primary line fails. Sometimes, the fail-over can happen even after a minute. There is no point in having two Internet connections from the same service provider and configuring them for fail-over because it’s highly probable that both of them will be down at the same time.

Normally, with routers it may not be possible to use both load-balancing and fail-over together. Only one of them might work at a given point of time and hence it is better to check before buying. Of course, they do support all the router features. There are specialized load-balancers and applications delivery controllers that can do both, but they are more expensive and generally meant for larger companies.

You can set-up load-balancing or fail-over in your small business or even at your home if Internet connectivity is very critical to you.

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