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Switches/Hubs/Routers

Discussion in 'A+' started by Fergal1982, Sep 10, 2004.

  1. Fergal1982

    Fergal1982 Petabyte Poster

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    OK. im aware that Routers act like the former two, except that it also allows external links (such as in the case of broadband). but can someone explain to me what the differences between switches and hubs are? i just dont get it!

    Thanks
    Fergal
     
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  2. Phoenix
    Honorary Member

    Phoenix 53656e696f7220 4d6f64

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    err, routers are not really like switches
    your probably getting confused with all these lame Router + 4 port switch jobbies going around


    A Router works at Layer 3 of the OSI model (Network) it directs packets based on IP address (and sometimes layer 4 info such as TCP ports), it can order packets based on importance by employing QoS and other such features, it is what we call an 'intelligent' device
    Router ports are seperate broadcast domains, thus broadcasts recieved on one port will not be propogated to the other ports, unless specifically told to do so

    A hub works at layer 1 generally, and is simply a method of splicing a load of wires together, although packaged in a nice box, thats pretty much all passive hubs do

    a Hub is a bus topology, everything is connected to the same 'wire' although it is usually packaged in a nice box with multiple ports
    everything connected to the hub is considered to be on the same 'collision domain' thus packets are recieved by all hosts, and all hosts use an interrupt to 'listen' to the packet and see if its for them, if not they drop it and continue, obviously on a large network this can cause numerous problems and congestion
    there are two types of hub, active and passive
    active hubs generally regenerate the signal when they recieve it, thus acting as a repeater as well and extending the network segment
    passive hubs just take data and broadcast it out on all ports

    A Switch works at Layer 2 or the Data-Link layer, they use MAC addresses for source and destination information, and are generally faster than routers of the same calibre

    Switches on the other hand are seperated by the switching fabric (making them a star topology)
    each port on a switch is a seperate colllision domain, thus packets transfered are only passed down the appriopriate port to thier destination, and other hosts are not interrupted, switches maintain a mac address table which maps mac addresses to switch ports so they know which ports to pass data down, switches are generally much faster than routers, and often are marketed as 'wire speed' devices, meaning there is close to 0 latency on some (ofcourse this is only when using perticular switching methods, but thats beyond the scope of this answer) ofcourse any networking device always adds soem form of latency
    Switches to not create seperate broadcast domains, and a broadcast will be propogated to all ports, hence switches are still suceptable to broadcast storms


    that brings us to the end of networking equipment 101 ;)
    hope it helps
     
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  3. nugget
    Honorary Member

    nugget Junior toady

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    Thanks Phoenix. Very clear and concise.
     
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  4. tripwire45
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    tripwire45 Zettabyte Poster

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    What he said... :)
     
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  5. noelg24

    noelg24 Terabyte Poster

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    Talk about in depth....
     
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  6. Phoenix
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    Phoenix 53656e696f7220 4d6f64

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    actually that was just the basic overview lol :)
     
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  7. tripwire45
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    tripwire45 Zettabyte Poster

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    Actually, Ryan isn't kidding. There's a lot more to know about those various devices. I once had to write some content regarding "routing switches" and it was amazing how much research I had to do to fulfill the requirements. I think this is why I learn so much more by writing about a subject than by reading about it.
     
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  8. punkboy101
    Honorary Member

    punkboy101 Back from the wilderness

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    That's a good point Trip, if your writting about something for others to learn from, you really have to understand it, and convey it in a fashion that people will be able to understand.

    It is a true skill being able to write about (sometimes) complicated subjects in a fashion that people that are new to a subject can understand.
     
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  9. Fergal1982

    Fergal1982 Petabyte Poster

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    sorry guys. i meant to read this when phoenix posted it, but put it off cause it looked like a mindf**k and forgot all about it. ok....

    so a hub is the internalized bus topology (when all pc's are connected to a single main cable with terminators at either end) making it a star bus. whereas a switch actively connects two talking pc's into a 'private' bus. right? meaning that if i had four pcs and 1&3 were talking and 2&4 were talking there wouldnt be interference from each conversation and they would be able to communicate at full speed? but im still a little lost on the router.

    so is it best to just use one type (switches/routers - im assuming you wouldnt recommend hubs in a network for more than a home user and one or two pc's without using the network intensively)? or should you use a combination of the two?

    Sorry guys

    Fergal
     
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  10. Phoenix
    Honorary Member

    Phoenix 53656e696f7220 4d6f64

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    to be honest hubs are pretty hard to find these days lol

    and routers are totally different, people are getting confused because its the in thing today to sell routers with built in 5 port switches for those home user scenarios where everyone has more than one PC

    thats fine, but we have to remember thats a router and a switch

    the switch connects the devices on the LAN

    the router routes the traffic from the LAN to the the WAN (ADSL/CABLE/T1 Line/Whatever)
     
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  11. Fergal1982

    Fergal1982 Petabyte Poster

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    so your router is basically the ADSL modems, etc????? is it actually possible to get routers without the built in switches? even the netgear router on the overclockers site has a 4 port switch built in!

    so the only option is a router/switch, and switches for expanding the network? although there is an adsl modem from netgear on the site which has an ethernet connection, so would you class that as a router then? (on a related matter, ive noticed that the modem i mentioned, Netgear DG632 ADSL USB/Ethernet Modem only supplies 8 Mbps connection speed, is that just for the xbox? or is it for anything connected to it? if it is, surely then it would be better to get a gigabit capable router?????)

    argh!!!!!!! my head is gonna explode, this is soooooo confusing

    sorry guys

    Fergal
     
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  12. Phoenix
    Honorary Member

    Phoenix 53656e696f7220 4d6f64

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    depends on the router you buy,

    alot that are designed for ADSL are routers/switches/ADSL modems built in

    some are juse Routers/ADSL modems

    id go for a router/adsl modem if you know your not going the cable route, and plug that into a 5 port switch or something, hell if you can only get a switched router then go for that and just plug that into another switch, i find it more versatile

    yes, you can get routers without 5 port switches :)
     
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