how bad is mixing/cascading slower older networking gear

Discussion in 'Networking' started by Twice_Shy, Feb 11, 2017.

  1. Twice_Shy

    Twice_Shy Member

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    So assuming I have alot of ethernet connected devices to hook up which is very nondemanding network loads (even 10mbit per channel is enough for things like SD quality video, shared webbrowsing on an intranet that's mostly simpler text, compressed audio - and 100mbit certainly plenty per single channel if all it is is browsing even fancier HD stuff) i'm wondering about the wisdom of using a random mix of older consumer class, older server class switches, maybe even lowly hubs in a ghettonet as opposed to obviously what an ideal would be - wiring every port for 1gig to one or more central 48 port switches in an equipment closet.

    Some of it is wondering if I can simply save on cabling, like if I find some 24port fast ethernet switch that maybe has 2-3 gigabit upstream ports, and I need 24 devices in that one room, is there any reason not to cascade routers like that. (turning off even the router at night when none of the devices are in use, like in an office)

    Or whether things like intelligent 10/100/1000 sensing ports on a switch to a slower device will ever bring down the speed of other devices local to it, or if that doesn't happen on anything remotely new.

    I'm fully aware that older slower ethernet modes are going to be bottlenecked by the slowest paths between two locations, i'm just wondering if there are potentially additional problems created in terms of jitter, latency, collision, or terms I don't even fully understand yet. (i'm no network engineer, I freely admit i'm just a hack who knows about computer stuff self trained) I've literally got boxes of old networking gear that i'm trying to find a use for that occasionally I find someone who might be able to use it, but would need help setting it up, and if hacks like a gigabit consumer router, to an old 24 port 100mbit switch on one channel for their office SIPphones, with one going to a local hub because they just needed a few extra ports over the 24 it supports is going to munge up everything i'd rather know.

    I'm sure i'd learn all this the hard way once I try to set things up but I wouldn't even know why it's failing since i'm not a network engineer. I'm sure a network engineer could save me time by giving guidelines of what not to do and why telling me why it wont work that way though on a ghettonet. :)
     
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  2. i386

    i386 Well-Known Member

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    I don't know where to start :D

    Hubs are a bad idea if you have many hosts. As soon as two devices start sending data and detect corruption they will send a jamming signal.
    Carrier sense multiple access with collision detection - Wikipedia

    Older gear = more heat = more noise
    Depending on how old the network devices are, they will generate more heat and draw more power with 10/100mbit ports than curent 24x 1gbit + 4x 10gbit sfp+ switches.
    To cool these devices small fans with 4k+ rpm are used. You don't want to have them in an office.

    For the phones you will need a switch with poe (power over ethernet) -> more heat -> more noise.
     
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  3. Twice_Shy

    Twice_Shy Member

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    Oh I know about hubs, I only mean downstream. If someone's conference room has 8 SIPphones, they use so little data i'm tempted to throw all of them on a single 8 port hub and run one wire instead of eight out of the room. Downstream the main switch there shouldn't be any collisioning interference, right?

    Heat is like speed - known issue - mostly worried about "will it function" rather than will it function elegantly. :) Such situations should be considered more temporary and meant to be upgraded later.

    Mentioned alot more than hubs too. :D Though whether I cascade hubs, or switches, or other routers, alot of it is tree trunk --> limbs --> branches instead of directly wiring to a central office closet.
     
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  4. Tom5051

    Tom5051 Active Member

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    Gigabit switches are so cheap, why would you want to use a hub??
     
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  5. maze

    maze Active Member

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    Its not worth the hazzle.. and even 8 sip phones Can mess up your hub :) - if enough broadcasts occur, your hub Will suffer.

    In general, daisy chaining switches isnt a good idea. Always have a "core/distribution" layer. I'v Seem quite a lot of older D-link gear broadcast random data into a single layer2 network. Was really not very good and slowed things down a lot.
     
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  6. fractal

    fractal Active Member

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    The only time I use a hub these days is when I want to sniff a connection and don't want to read the manual on how to set up the monitor port on a switch. They should not be used in any modern network.

    I am very fond of the 8 port POE powered switches for remote conference rooms. I freely admit I spent too much money to ensure I can use them in my house. But, if your central switch IS POE capable then they make a great way for a few low traffic devices share a single cat5 cable.

    Another thing to consider is managed, either fully or smart, vs unmanaged. The average home user can get away with an unmanaged central switch since everything goes to it and they can go and look at dem blinken lighten when something goes wrong. Management and diagnostics become increasingly important with the number of devices / points of failure.

    I used to put 20 dollar, eight port switches every where I had one wire and needed more than one thingie. I kept replacing them when they broke until I settled on the HP 14xx series of unmanaged switches. I have been replacing those with 8 port, POE powered HP smart switches. It gives me some comfort knowing the eight port switch in my bedroom will still be blinking and powered from the POE switch with the UPS in my hall closet during a power failure. Not sure why since nothing connected to it will have power, but it is comforting ;)

    The old five hop rule from the hub days do not apply to switches but I still try to keep my house to 5 hops or less just because that's an easy number. I have that many fingers on each hand..
     
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  7. Tom5051

    Tom5051 Active Member

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    Actually I haven't come across a network hub since 2001... So yer, they are massively old technology and I would never use one with a modern switch.
     
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  8. mstone

    mstone Active Member

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    Just recycle the old gear. A low cost gigabit switch will outperform some old device, and use substantially less power. Other than that, if you're happy with the bandwidth constraint of the backhaul link, you're fine; the rest of the network won't magically slow down because one part is daisy chained.
     
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  9. Twice_Shy

    Twice_Shy Member

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    1 Because I already have boxes of them

    2 Because i've helped set up some really ghetto-class SOHO networks at the bottom end of the foodchain and the only thing that even had me make even $12/hr after the work was that I didn't have to buy some $50 gig switches

    3 Because it tests my theoretical understanding, if the model in my head says "there shouldnt be a problem" and there is, I need to correct my understanding. VOIP is so low in bandwidth needs i'm wondering why not, especially when it's the difference maybe between a 24 port core switch and a 48 port or more setup.


    Really? Okay thank you for sharing - see thats what i'm trying to get, specific understanding of why it wont work, instead of just "dont be cheap". I sent multiple luggage full of tossed networking gear to Africa with a missionary friend of the family before with instructions of how to set up a ghetto net to get some kids online via one local community connection and they are absolutely happy to have it - there's a place where the difference between $3 and $15 matters alot when it's repeated over and over.

    I hate to see things wasted when someone can make alot of use out of it, and often be incredibly content when the alternative is nothing.

    Could you offer any guideline of what hubs or/and switches might be usable under those circumstances, how to avoid/block broadcasting (if possible) or how to split one connection into multiples within a room? I'm curious because your opinion of not chaining switches contrasts with the person below, and since my understanding is "shouldnt be a problem" either i'm wrong and need correction, or there's just some other aspect I dont understand.


    Is there any problem cascading switches like that though?



    Yes but even cascading older 100mbit switches is relevant. In my mind even hubs should work downstream a switch and the bandwidth of things like SIPphones should be so minimal that even 10meg 8 port hubs shouldn't matter.


    I prefer to either make lunch money on a ghetto setup that's headed to the trash bin anyways or send it to places people can still use working gear to do some good. I'm just wondering what the limits are and why.
     
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  10. Tom5051

    Tom5051 Active Member

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    Why come here asking for advice when it's plain as day that you already plan to use shitty old hubs despite numerous people pointing out the issues. Just seems dumb.
     
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  11. whitey

    whitey Moderator

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    Sorry I got a paragraph or two in and started having nightmares...when 48port GigE switches are cheap as dirt ($100-150)...why even bother IMHO, couple of stacked 48 porters connect a NICE size office/co-lo/lab up quick like w/ nearly 100 conn's and only two devices to manage ='s less points of failure/potential congestion chokepoints/network gremlins/etc.

    BOOM, done from my humble opinion!

    I value my time greatly :-D

    EDIT: One thing I will say and it's been touched on here is that something like a good old rock solid Cisco 3750 PoE 10/100 fast ethernet switch is aiight to hang a bunch of voip phones off of, no need for GigE for those for sure if you have a capable switch laying around. Definitely minimize 'device sprawl' else network ghosts be runnin' rampant on ya good sir, I GUARANTEE IT, especially if your not a NE, next thing you know you'll have a STP loop or bridge something the wrong way (creating a network loop/broadcast storm) and lose your mind trying to troubleshoot it :-D
     
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    Last edited: Feb 13, 2017
  12. i386

    i386 Well-Known Member

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    Hubs are bad because they don't do full duplex: only one client can send or receive data.
    [​IMG]

    Cascading switches: uplink limitations, if somebody copies a large file it might consume all the bandwidth of the uplinks and leave nothing for the voip clients or other clients
     
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  13. maze

    maze Active Member

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    How much is your time worth? - or maybe the people having to use the gear every day and wait for it :)
    - Not being racist in regards to your africa story. But time has a different meaning in some countries.

    Thats normally how i make up if I need to buy new gear.

    Only way to avoid broadcast domains is by doing vlans.

    As @whitey said. Why even bother when you can get a 48port gig switch for like $100-150 usd .. the time you waste getting your daisychained switched to work, and troubleshoot (or even just finding where the user is connected) the first time someone comes whining to you.. you'v made the investment back.
     
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  14. fractal

    fractal Active Member

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    The theoretical concern I would have with a hub for VOIP is not bandwidth. It is jitter and latency.

    A switch will give deterministic latency. A hub will not. VOIP phones often synchronize their clocks to their upstream provider and, depending on model, may all decide to send out their 20mSec sample at the same time. This will cause a collision and random backoff in a hub. The key being "random".

    Knowing whether this is a problem with your application would take me more effort than recommending a 20 dollar switch. But, I can see how in your case it might be worth looking into the affect of jitter and latency on your VOIP link. A local domestic link is less tolerant than one provisioned for a satellite hop to Africa. Your application may not really care about the extra jitter from the hub.
     
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  15. voxadam

    voxadam Member

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    I just ran across this thread and am already having flashbacks of broadcast storms on old 10 meg hubs.

    I need a drink.
     
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  16. xnoodle

    xnoodle Active Member

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    Don't forget about the days prior to auto MDI-X.
     
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