View Full Version : Difference betveen a switch and a Hub??

11th December 2001, 14:25
Recomendations on a good site with info on this, or do we have an expert on the forum? :)

11th December 2001, 14:44
You can compare it to the network protocols NetBEUI (HUB) and TCP/IP (SWITCH)!

11th December 2001, 14:46

Best plain-English explanation I've seen is:

A hub is a totally dumb device. If it gets a data signal, it just forwards it to everybody and hopes someone will pick it up.

A switch is just barely smarter. If it gets a data packet, it will try and find the device it goes to, and then send it to that device only, but the device MUST reside on the same subnet. A switch wont send data packets to computers on different subnets

A router is just barely smarter than a switch. It only gets a data packet if the destination computer isn't on the same subnet or LAN. The router then figures out where in the world that computer is located and then sends it in the right direction. -<a href="http://www.tek-tips.com/gviewthread.cfm/lev2/8/lev3/58/pid/541/qid/148477">Shnypr</a>

Hope this helps.

<small>edit: added practicallynetworked url</small>

11th December 2001, 14:53


PC's to a hub

Hub's to a switch

Switches to routers.....

:confused: :eek: :rolleyes: :cool: ;) :D

11th December 2001, 15:03
Here the first computer prints to the printer, but the message is broadcast to all of the computers on the network. A hub works like a telephone party line. Only one computer can talk at a time.

Now the first computer and printer make a private connection during printing, while the 4th computer transfers a file to the 5th computer over another connection. A switch works more like our modern phone system. Computers can talk with each other on private connections so that multiple conversations can be carried on at the same time.

Shared Ethernet Hub

Total network bandwidth is limited to the speed of the hub, i.e. A 10Base-T hub provides 10Mb bandwidth max, no matter how many ports.

Supports half duplex communications limiting the connection to the speed of the port, i.e. 10Mb port provides a 10Mb link.

Hop count rules limit the number of hubs that can be interconnected between two computers.

Less expensive per port.

Switched Ethernet Hub

Total network bandwidth is determined by the number of ports on the switch. i.e. an 8 port 100Mb switch can support up to 800Mb/s bandwidth.

Switches that support full duplex communications offer the ability to double the speed of each link, i.e. from 100Mb to 200Mb.

Allows users to greatly expand networks; there are no limits to the number of switches that can be interconnected between two computers.

Price/performance is worth the slightly higher price.

EDIT: Sorry it took so long to find the pictures I was to lazy to upload them to my own space! :o

11th December 2001, 15:21
though switches also have a backbone which often isn't as fast as the max bandwidth times the amount of ports on the switch :)

11th December 2001, 15:56
Guru has a really good explanation up there. What does it mean to you?

In a hub, use of any bandwidth affects everyone's bandwidth, whether they care about the data or not.

Simplified example:

So, if you have computers A, B, C, and D. D is the machine with a connection to the Internet. Now start a massive file copy between B and C, while you try to browse the web/play games on A.

On a hub, A and D will be bogged down by B & C''s transaction. On a switch, B & C will talk only to each other, and the A-D communication will not be congested.

Also, if you're on a hub, you can set up your NIC in promiscuous mode, and watch what everyone else on the hub is doing. My apartment building was on hubs for a while, and people that used un-encrypted protocols were easy marks. Running a sniffer for about 5 minutes got me lots of logins and passwords. I didn't use them, but I sure don't use telnet anymore (ssh for me!).

11th December 2001, 18:38
Mike could correct me on this if I'm wrong here, but is not a hub set up to work only in half-duplex mode (signals can only go one way at a time), whereas a switch can work in full-duplex mode (signals can go both ways simultaneously)?

11th December 2001, 19:45
That's right. Standard "broadcast-style" hubs can only do half-duplex. If the NICs and switch (also known as a "switching hub", confusing huh?) support it, then you may be able to get full-duplex. Drivers, auto-configuration, line noise, and tons of other stuff might stop it from happening though. Only a few applications really benefit from full-duplex though.

Dr Mordrid
11th December 2001, 20:35
Putting into practical terms:

the hubs take longer to "find" another computer on the network, even if there is just one. Switches, besides being faster at finding another computer, are also full duplex given a full duplex capable NIC. This is especially important if you're sharing a net connection across the LAN or using TCP/IP protocols for an intranet.

Dr. Mordrid

12th December 2001, 04:43
If you're planning to buy one just go for a switch the price difference isnt that much.

Guru's post explains the difference very good (Hub is also called a multipoort reapeater.). And if you're planning a LAN- party definatly go for a switch.

12th December 2001, 06:12
NetGear F116/F108/F105 :)

All 10/100mbit switches, very good value (at least here in the UK). You can get the 16 port switch (116) for £100 + tax.

I'm probably getting one myself, to replace a budget 16port 10/100 hub.

They are unmanaged btw, don't know much about managed switches (though don't buy a manage one if you aren't planning to manage it, it'll end up like a hub :))


12th December 2001, 10:19
Unmanaged Switches do not rely on a Router for addressing.

For smaller networks, an unmanaged switch is fine for a small Domain or Workgroup.

But when you go over a certain point (Roughly 50 or so ports) a Router (or two, or more; software or hardware-based) is essential for managing a network.

As an example, if you put too much of a load on a switched network (not as hard as it sounds), you can create a collision problem caused by multiple streams sent to the same port (like for instance a Mail Server or Internet Gateway), that the Router cannot keep adequate control over: in an extreme situation, it is possible to create a "runaway", where the Router spends all of it's time trying to manage just a few ports and the rest of the network tries to fend for itself by trying to find pathways using multiple broadcasts...Collisions mount to the point where one or more switches either locks up or the backbone fails.

For this reason, among others, larger networks tend to use 100 megabit (Or Gigabit) full duplex connections sparingly. For a bunch of typical workstations doing even the most network intensive tasks 100MB is overkill, with a few exceptions, of course: video editing, sound and CAD programs can eat up a bunch of bandwidth and nbeed high speed connections (But in that case you would segment the network to keep the few speed freaks away from the rest of the thundering herd)...multiple I/Os of only a few packets of data (under 1 Megabyte per I/O) over a full duplex connection can bring a Router down in a hurry. But if you "dumb" down the ports to 10MB Half Duplex, it gives the Router a LOT more time to do it's work, and the users of the workstations will never know the difference unless they like their p0rn in BMP format. It's a question of usable bandwidth versus practical application.

12th December 2001, 16:38
Ok, ok, I've got it...

Then I will definitly go for switches when the network grows at work....