What is network infrastructure and what is a hybrid network?

It will be easier to understand what a hybrid network is once you know what network infrastructure is. To get a full understanding of network infrastructure, Whatis.com has developed a Learn by definition method of learning (or "Learning path") for this word. If you click on the network infrastructure learning path, you will be taken to a list of other definitions, starting with infrastructure. If you follow the list of definitions from the landing page, you'll come to a fuller understanding of infrastructure networks -- the plumbing, so to speak, that connects computers and users together.

To answer the second part of your question, "hybrid" means "mixed" -- so a hybrid network is a mix of what makes up a network. According to TheFreeDictionary, a hybrid network is a network that contains network hardware and equipment -- or network infrastructure (to relate back to the first term) -- from multiple vendors. In example, a network that includes Juniper Networks' switches and HP ProCurve's data center management solution would be considered a hybrid network. Some infrastructure networks only contain network equipment from one vendor -- like Cisco -- because the pieces are interoperable and would therefore avoid mis-communication between devices; it could also create a faster network (in theory). Being locked in to an expensive vendor, however, leads companies to choose the hybrid network route, because it can cost a lot less and more appropriately fit the needs of the business.