Router vs Bridge vs Hub vs Repeater

In layman’s terms (or otherwise), what is the difference between these? By Router, I mean the business-class ones, not the wireless ones at CompUSA (or are they same)?

In general:

router: creates a border between networks (layer 3 groupings) and is the “postman” for communications between the networks. Business class routers can do many things in addition to this, but basically they serve the same purpose as ones at CompUSA.

bridge: typically a bridge just connects computers together in layer 2 groups similar to a hub. More specifically, a bridge can mean “to change”. For example, a bridge can connect a token-ring segment to an ethernet segment. A bridge serving this purpose would only have 2 ports (or one per type of layer 2 segment) while a hub or switch would have lots of ports (4, 8, 16, 48 or even more).

hub: connects computers together. Most of the time when this term is used, it implies a single collision domain. Think of this as talking on a walkie-talkie; really only one person can talk at a time, otherwise things get confused. Ethernet “switching” improved over basic hubs by creating more “talk paths” and reducing the frequency when people are talking “over” one another (collisions).

repeater: basically just takes an electrical input on one side and regenerates the signal and sends it out the other side. This helps to extend the range a communication can be sent down a wire. Note that routers, bridges, hubs and switches also act as repeaters as part of their function (take signal in one port and forward it back out another port).

I hope this helps.

Actually, it does. How do “switches” fit in that mix. I saw you touched on them when describing hubs and repeaters. Is it a combination?

A switch is basically a smart hub. Over time it learns which ports are connected to which computers, so if it sees a packet for a computer it can forward it only to that computer’s port and leave the other computer’s ports free.

Public Data Switches read the header information in the customer data and direct the data packets to their proper destination. In this respect, switches can be seen as changing or determining the end-to-end circuit path of a telecommunications link.

Elaborating a bit on Rysto’s comment, if a hub receives a signal, it will rebroadcast it to every computer on the network. A small identifier will let the intended recipient accept it and all others will ignore. The computers can transmit at any time, but if two transmit at once, the hub detects the interference and reports a “collision”. It will transmit a signal to all stations telling them to wait some random time (typically measured in milliseconds) before transmitting again. The hub will have a “collision” light on it. If it is on almost continually, the traffic is too much for the hub and too much transmission time is being wasted. At that point, consider an upgrade.

A switch, by contrast, will recognize which machine is the intended recipient and transmit a message to only that machine. The handling of the messages is more sophisticated, with no wasted time on collisions. Hubs are okay if, say, you have a single network jack in a room and want to attach more than one computer, using the hub as a splitter. If traffic isn’t too heavy, it’s a nice cheap solution. Switches, though are getting more economical, and now routers with switches built in (to allow multiple computers to share a high-speed internet link, for example) so it’s not like there’s a huge additional investment for dubious additional features.

This is all somewhat simplified on technical details, of course.

You asked for “laymen’s terms,” so I hope this isn’t too simplistic. Another way to think about these devices is how “intelligent” and efficient the device is – and consequently, how much work it can offload from other computers and devices on the network. See this page.

Computers on a network communicate with each other by breaking data into small chunks (normally “packets”) that travel over the network one piece at a time. When one of these packets reaches a networking device (hub/switch/whatever), the device has to decide what to do with it:
[li]A repeater just spits it out again, but louder. Useful if your network cable (or wireless connection) stretches over so long a distance that the actual electrical signal is getting weak and needs to be amplified.[/li][li]A hub takes that one chunk and repeats it to ALL connected computers on the network. Then the computers themselves have to examine the pieces and examine whether they should do anything. Each computer goes through a thought process like “This packet was meant for computer #, but I’m computer # It wasn’t meant for me, so I’ll ignore it.” This is fine for small networks, but when you start adding more and more computers, you end up with too much junk traffic.[/li]
A real-world analogy would be the Post Office photocopying every letter it receives and delivering a copy to every other person in the world, leaving it up to the recipients to determine whether the letter was addressed to them. Not the most efficient way to do things, and not the most secure either since everybody will see everybody else’s communications.
[li]A switch does what Rysto said, thereby significantly reducing the overall traffic in on network.[/li][li]A router is a better, smarter, more complicated switch. Using the postal service analogy again, a switch would be like a small-town neighborhood post office that handles 50 letters a day within the same town. A bigger metropolitan post office – a router – might handle 500 letters a day between different towns, and it has to determine the most efficient way of getting each letter (or packet) from its source to its destination. More complicated routers handle even more complicated situations, including security concerns, finding a different path when major backbones go down, etc., much like the way a major regional/international post office might have to deal with mail fraud, international mail, problems with the smaller surrounding post offices, etc.[/li]
Basically, the main differences between the cheap consumer routers and the more expensive small-business ones come down to reliability, number of ports, performance (how fast it can deal with each bit of network chitchat), and additional features. Both kinds can handle the same basic task, but the business ones (and some of the better consumer ones*) are more configurable and support custom firewall rules, port forwarding maps, etc.

As for the really, really powerful routers that run big businesses and the Internet itself, I don’t have any experience with them so I can’t say anything.

*An especially interesting consumer router is the Linksys WRT54GL, which can be re-flashed with custom Linux-based firmware that gives it more features than other consumer routers. That little device can run a SSH server (so you can use it as a mini-Linux computer), a RADIUS authentication server (for secure wireless networking), and a crapload of other things that normally aren’t available on consumer routers.

Do people even make hubs anymore? Even the cheapie $10 jobs I see are switches.

Probably not, but if the OP was, for example, looking for a way to link a bunch of computers together to play Quake with his buddies, a cheap hub from the local used-electronics store would suffice.

The difference between a router and a switch isn’t easy to explain in laymen’s terms.

A router routes based on IP addresses. Because IP addresses are assigned by how computers are grouped, this allows them to be manually pre-programmed with a relatively short list of IP address ranges (i.e. “All IPs between and go to this port, all IPs between and go to that port”).

A switch routes based on MACs. MACs are assigned uniquely to each network card and so a network can have many wildly different MACs, so rather than ranges, a switch stores a relatively large list of single addresses, which it adds to over time.

So you can see why you wouldn’t use a switch for a large network. The list of single addresses would get prohibitively large, and every time you sent something to an address not on the list, it would have to get broadcasted to EVERY computer.

And at the same time, a router is inappropriate for a small network because it is very expensive and not as fast.

To use the mail analogy more accurately: A router is like a post office, whereas a switch is like a company mail room.

Now what about a patch panel. Just an unpowered hub?

Nope, just a place that data cables terminate on one side, and allow Cat 5 cables to plug into on the other. Those are typically plugged into a switch. You bring all the cables in an office together at one spot, hook them up to the switch. Doesn’t actually have any communications functions.

The patch panel is essentially a bunch of extension cords, each with one end grouped together into one handy 12-, 24-, 40-, whatever- single block, and the other ends scattered off to various rooms. It’s a convenience if you need to bring all your network connections to one central point (which has been the standard for some time, though other configurations are possible) but the panel itself is no more capable of handling network traffic than a powerbar can generate electricity.

One router function not touched on is DHCP serving, which most routers will do (you can turn the function off if not wanted). This allows the connected computers to obtain a locally unique IP address, so that you don’t have to manually assign a different one to each machine on the network. A slight convienience on a small home network, but indespensable on a larger LAN.

But you asked for laymans terms:

Hub: Cheap way to connect a few computers togethor.

Switch: Slightly more expensive way to connect a few to a bunch of computers togethor, gives better performance than a hub, MUCH better performance if there is a lot of network traffic.

Router: A switch with a special port for a cable or DSL modem so that all the computers on your network can share one high speed internet connection. (they have other uses, but this is by far the most common reason most lay people would install one on a home network)

One more thing: You can “daisy chain” switches on an existing switch or router if/when your LAN needs to grow, so there is no need to buy the expensive bizillion port model because you fear outgrowing it.

I remember about two years ago a company my dad worked for had this problem. They had attached a packet sniffer to their “hub”, but couldn’t intercept anything. It turned out that their “hub” was actually a switch, and they couldn’t find any real hubs in the stores, so they traded the switch to my dad for a hub.

Switch: Slightly more expensive way to connect a few to a bunch of computers togethor, gives better performance than a hub, MUCH better performance if there is a lot of network traffic./QUOTE]
That depends on the nature of the traffic. If most of the traffic on the network goes to/from one (gateway) computer, there’s little the switch can do to improve performance.

They DO make new hubs, but they’re a dying breed.
Netgear still makes its venerable EN104TP. [1] My employer installs several a day.
Without disclosing my employer, I have a couple of scenarios at work where my only option is to hang an EN104TP or equivalent off of an enterprise’s Cisco switch and pipe a machine’s data in through that while a second machine eavesdrops on the hub.