What it is Redundant network?

A redundant network is one which has some extra capacity, in case certain components fail. It is just like having a spare wheel in your car. You don't need it all the time, but it is there, just in case one of the other wheels fail.

For example, you can have more cable connections between switches or other pieces of equipment than what is absolutely required for the basic working of the network. In this case, if one connection fails, it is possible that data can still be sent over another connection.

You can also has spare switches, spare routers, or spare servers, but that is more expensive, and in some cases complicated to configure. You must weigh the cost of these equipments, against the cost of network downtime.