This isn't very hard, but if you talk to vendors about their products and their competitors' products, you could become confused. At any given time, "managed" and "unmanaged" are terms that are defined by the person flapping their gums. It is one of those things that you may never find two people to agree completely on. It's a class of functionality, not a specific function, so there are no clear definitions. Unfortunately, the words can be used to mean "our products" vs. "their products."
In general, "managed" means there is network connectivity that allows errors to be reported. "Unmanaged" means that you have a black box that does a job without reporting anything into a network management system of some sort. It works until something goes wrong and then you have to go figure out what that "going wrong" is.
But "managed" can take on other characteristics too, such as the ability to remotely (or automatically) change the configuration of the system to changing workloads or error conditions. A hub that bypasses a malfunctioning port can be thought of as a "managed" hub -- even if it doesn't report the fact to a network management station.
There are NO unmanaged switches in Fibre Channel. The notion of an unmanaged switch is contrary to the whole notion of FC switching. If you are asking about Ethernet that could be a different story but I don't think so. I cannot imagine why somebody would build an unmanaged router. It goes against the grain of what higher-level network products do. Hubs can be unmanaged as their goal is sometimes to be the lowest possible cost with the least amount of complexity. (This actually became a real problem for FC because hubs could not be uncomplicated by virtue of the underlying FC communications structures).
For the most part, there are very few products that are unmanaged anymore, if somebody tells you a product is unmanaged, tell them you think they must be wrong and ask them to explain how in the age of cheap microprocessors you don't believe there are any more unmanaged products. If their answer has details then they might have a point. If the answer is along the lines of "just because" stop listening and move onto the next point -- you are probably being stonewalled.
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This was first published in September 2002