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  1. #1
    Senior since the 3 dot era
    Join Date
    Nov 2001

    Something About Ethernet Hubs and Switches

    Something About Ethernet Hubs and Switches...

    1) Why?
    Many times people here ask how should I network my boxes etc...

    2) What?
    This tutorial is about things you need to keep in mind when adding
    a switch or hub to your network.

    3) What not?
    There are other tut's on AO explaining how to network your boxes,
    what stuff you will need and etc. so I'm not going to explain that again.
    This tutorial does not claim to be complete, feel free to add or to comment.
    Legal notice: This tutorial may contain other proprietary notices and copyright information,
    the terms of which must be observed and followed.
    Information in this tutorial may contain technical inaccuracies or typographical errors.

    4) hubs and switches (switching hubs)
    4.1) Basic things about hubs and switches (you all know this)
    A hub is a device that will connect your computers with eachother.
    You will need straight UTP (cat5 or cat5e) cable to connect your pc to your hub.
    The same goes for a switch.
    What's the difference? Basicly a hub does not forward to an individual port. It sends data to all ports when there is a request. This means that when one pc sends something the others have to wait until the network is free again.
    Otherwise you will get collisions. You can imagine that on a high traffic network
    the hub will have many collisions. Then a switch becomes handy.
    A switch forwards the request to the port it's meant for. A switch is an intelligent device learning MAC's, this means that it will send the data to the port it's meant for and not to everyone. In other words: your network runs (a lot) faster, and more stable.
    Switches are indicated as 10/100 (or 10/100/1000) switch,
    while hubs usualy will have 10Mbps speeds.

    4.2) Most people here at AntiOnline advice to purchase a hub cause the price
    for switches has decreased to the level of hub prices and cause they are faster.
    So why still get a hub? or why not I will give a few ideas.

    What's the traffic? - When your network traffic is low (Or high).
    Example 1: There is a switch with only two normal desktop computers with low traffic,
    like internet sharing. You will not generate enough traffic to make your switch run
    faster then a normal hub.
    Second, it does not matter that you cannot get 100Mbps, cause 10Mbps is fast enough for
    internet traffic since most users have a slower internet connection.
    Even xDSL or cable does not exceeds 8Mbps in home user situations.
    Most home users only have 1Mbps download theoretical max speed.
    This means that 10 Mbps is 10 times faster then your fastest internet download!
    A switch will not increase your speed for those issues. It can even slow down your performance.
    A switch needs something around 20-30 % usage before it gets its quick response times.
    Therefor if you have a 24port switch with only 2 boxes connected to the internet your response times
    can be worse then if you used a simple A-brand 5port Hub.
    -> The important / key idea you need to read in this example is that when your overall traffic is low,
    and you need to link only a few pc's, the better choice is a hub.

    Let's take the same 2 computers from example 1
    Example 2: You have those 2 boxes sharing 1 internet connection but at regular times you use
    box 2 to backup box 1 hdd. And you use box1 and box2 while gaming with your friends on your network.
    Or you want to use a DVD or CD Writer across the netowrk.
    Both gaming, cd writing or a complete system copy will need high speeds and bandwidth requirements to run
    comfortable. In this case your 5 port hub will be a loser! The switch outrages the hub several times,
    not only the hub response times will be slower since network traffic increases. (For instance when friends
    connect their laptops). The 10Mbps will be slow, perhaps to slow.
    A decent switch can handle this situation with ease

    Example 3: You want to connect several hubs with almost all ports used.
    You will need a switch. A switch can be the main part for "your backbone".
    A hub is probably not going to work.

    4.3) Other things
    - Noise. I'm considering noise cause sometimes this can be important. When you need to place an "always on"
    device sometimes noise can be very annoying. For example in a music studio, a student room,...
    Many switches have fans, especially the larger managed ones. If possible, try to get one with convection cooling.
    Convection cooling = silence. Make sure, however, your equipment gets appropriate cooling.
    Leave at least 3 cm at each side for ventilation.
    - Look at the mdi/x settings. Do you need cross-link cables to link? Or can you use normal UTP cable?
    - Power supply, is the power supply internal or external? Does it has the right voltages. Make sure you purchase
    a device with the right power needs. (110 for USA, 220-240 for Europe)
    - Look at cable types and protocols. Most will have the standard RJ45 ports and Ethernet 802.3 but you never know.

    4.4) Summary
    -Hub or switch? -> look at your needs.
    -How many ports? -> are you going to purchase extra hardware in the (near) future? Yes, make sure you have enough ports
    to cover your expansion or your switch or hub provides enough expansion capabilities (like uplink ports)
    -Fan or convection cooling -> look at the place you want it to install

    Those where some little ideas to help people getting the product they need...


  2. #2
    Join Date
    Oct 2002
    From a security perspective, a hub is bad because since it fowards traffic to all ports it enables an attacker with one host to sniff all the traffic on the network. A switch will not allow this to happen. I agree with *VictorKaum* however that for smaller networks it doesnt matter.


  3. #3
    Senior since the 3 dot era
    Join Date
    Nov 2001
    Yep, Xenon, thanks for the heads up, I forgot to mention that.
    Indeed a hub will allow every computer on the local net to "sniff" every packet simply with setting the network card in promiscue mode.
    With a switched network this becomes *a lot* more difficult. Therefor if you do not want that your room / house mates see what you are doing / what you are downloading ... get yourself a switch.

    shame on me not to add this first.

  4. #4
    Senior Member
    Join Date
    Jan 2002
    And one other note (which has been touched on by a couple of threads in the IDS forum)

    If you need to run a sniffer yourself for IDS purposes (or indeed any other purposes such as billing in the case of ISPs, traffic monitoring etc) then you need to either use a managed switch which has a capability of using a "monitor" port or something where it sends all the traffic, or install a hub.

    The easiest way is to stick a small hub with only a few ports between your main switch and your router or firewall, then stick the IDS/ sniffer box off there.

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