A hub is a device that connects together all the segments of a single network. Every device is connected, each with a single cable, directly into the hub. Any and all transmissions that come in on one physical port will be rebroadcast out all the others (bear this little tidbit in mind when we discuss the other devices). That means if one device sends it, all the other devices will receive it. This setup generally uses 10BaseT cabling. Like Network Interface Cards (see below), hubs come in both standard (10 Mbps) and Fast Ethernet (100 Mbps) versions. Also, generally speaking, if your network is small, say less than 10 devices in a peer-to-peer, then a hub may be all you need. Larger networks call for meaner hardware. Keep reading.
Hubs operate at Layer 1, the Physical Layer, of the OSI Reference Model.
There are several “types” of hubs. Passive hubs just act as an unobstructed pathway for data, enabling it to go from one device or segment to another; it does not in any way regenerate or process signals. By contrast, active hubs do regenerate and process signals, much as does a device not mentioned on CompTIA’s Network+ objectives, a repeater. It’s not unusual to hear the term “concentrator” when referring to a passive hub and “multiport repeater” when talking about an active hub. Another type of hub is the “intelligent hub.” These hubs offer extra features that allow an administrator to monitor traffic passing through the hub and to configure each port on the hub. Intelligent hubs are also typically stackable, built so that you can stack them physically one atop the other, which conserves space. Another term you’ll hear referring to an intelligent hub is “manageable hub.” Yet another type of hub is the “switching hub,” which actually reads the destination address of each packet and then forwards the packet to the correct port. This device approaches being a true switch (see next).
You should be aware that the hubs used in Token Ring networks are called Multistation Access Units, or MAUs, aka MSAUs. This device physically connects network computers in a physical star topology with a logical ring structure. You can have up to 33 MAUs in a chain. MAUs are chained together by connecting the "Ring Out" port of one MAU to the "Ring In" port of another, then connecting the last MAU's Ring Out port to the Ring In of the first MAU in the chain. This forms a complete loop, or ring. MAUs deal with one of the drawbacks of token ring networks. In token ring networks, a single non-operating node can break the ring. The token just gets "stuck." A MAU solves this problem by "shorting out" nonfunctioning nodes, thus maintaining the ring structure.
Advice
on Choosing a Hub
Lyksinks
Examples of Hubs
How to
Setup a Peer-to-Peer Network Without a Hub
Switches do have a thing or two in common with hubs. Both devices connect multiple segments of a single network and both allow those devices to talk to each other. Like hubs, switches primarily are used in Ethernet environments and support 10 Mbps, 100 Mbps Ethernet, or both. Switches even look a lot like hubs. There is, however, one key difference: a switch makes a direct connection between the transmitting device and the destination device. Compare that to a hub, which rebroadcasts signals out from all ports, so all the devices on the network will see the signal. On a switched network, only the sending device and the receiving device see the signal. This leads to the main benefit of a switch over a hub—no bandwidth wasted by sending signals to devices that don’t need to see the signal.
Switches operate at Layer 2, Data Link, of the OSI Model, which is another key difference between a switch and a hub, a device that operates at Layer 1. Just remember that a switch reads the MAC address to determine where a packet is going. The MAC address is very much a Layer 2 feature, so switches operate at that layer.
That said, there is an animal called a Layer 3 Switch. This is actually a superfast router that does Layer 3 forwarding in the hardware. What you have is a device that acts like a switch but uses IP or network addresses, which are Layer 3. A Layer 3 switch allows you to use switching hardware for routing, which is faster because it eliminates a lot of the latency you'll normally see in routers.
Difference Between a Hub and a Switch