Any network Hardware Gurus?

Discussion in 'Hangar Talk' started by Flyboy, Feb 9, 2007.

  1. Flyboy

    Flyboy Pre-takeoff checklist

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    I'm about to replace an old cheap dell network 12 port switch that was pressed into service when the HP 24 port switch was maxed out. We moved the switches around (always makes me cringe when you move something thats been sitting for years) added 2 extranal network drives that filled up the 12 port switch and now we are getting random network drops. It's not always the same port or connected to the same switch so, not being a network expert - I want to punt.

    Instead of replacing the small switch I want to get on 48 port switch and replace both old switches but there in lies the rub. I'm finding prices from a few hundred dollars for netgear to thousands of dollars for cisco. We have a pretty simple network. The dsl line is connected to a linux firewall that is connected to a 24 port switch and lines are run to it to small 8 port switches around the building or directly to PCs. I don't have a nead for fiber optic lines (that I know of). We run a 10.0.0.0 IP system which is what was set up when I came to work here.

    My question is for those of you that have experience with them, will the 30 to 500 dollar 48 port switch work fine in my situation? I can't see what difference a 2,000.00 swithc would make as our network traffic is mostly email with sending a few files to other machines over the network.

    I'd appeciate any comments. Thanks!
     
  2. TMetzinger

    TMetzinger Final Approach

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    There are two main differences that drive up the price in an ethernet switch:

    Backplane speed - since a switch is supposed to be able to forward packets from any port to any other port at wire speed, the backplane speed determines how many port pairs can be transmitting at once. Ideally, with a 48 port fast ethernet switch, you'd want 2400 Mbps of backplane speed. Many "switches" will have less bandwidth. You still get some advantages of switching, but not the full speed you were expecting.

    Management - a cheap switch will have little to no management. An expensive one will have the ability to keep statistics, extensive diagnostics, interface with management systems like OpenView or NetView, and implement various security features as well.

    So... If you're not running high-volume traffic like backups or database replication, and you don't have centralized file servers, then you're probably correct that a cheaper switch won't hurt you.
     
  3. gkainz

    gkainz Final Approach

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    feedback from a couple of the geeks at my office:
    -----------------------------
    "You could first try replacing the 12 port with a 16 port DLink or similar (low cost) switch and see if the dropouts stop. Many small offices run just fine on a string of DLinks."

    and

    "Depends on what layer the switch is. Layer 2 or 3. It should work but as in all things, you get what you pay for. The $500 switch won't be a managed switch."
     
  4. mikea

    mikea Touchdown! Greaser! Gone West

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    I don't know why plugging in more devices would give you random network drops unless a) the key word was "cheap" or b) It's not a switch. It's a hub.

    A hub will have a collision light on it. That light should blink occasionally but never stay on for as long a second. If it does you have too many devices talking at once. Get a switch, which segregates each into its own network.

    I've got a 5 port SMC Gigabit switch here at home which has been working flawlessly. SMC has 16 and 24 port 100mb SMC switches that aren't too expensive.

    I was just looking at NewEgg thinking of getting another one, then I noticed that only my two PCs are going at Gigabit so I can do fine with a 100. My SMC GigE is around $79.
     
  5. TMetzinger

    TMetzinger Final Approach

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    A follow-up - what do you mean when you say "random network drops"?

    If you mean that the link goes down on ports at random, then a new switch of whatever price should fix that problem. If you mean that performance get slow occasionally, then you may have a capacity issue that would require a more expensive replacement. But unless you're moving very large amounts of data across them, I'd doubt you have a capacity problem.
     
  6. Flyboy

    Flyboy Pre-takeoff checklist

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    Well the HP we have is supposed to be a managed switch but I've never managed it or any other switch. :dunno:

    The netgear and other low end ones do provide a small level of management via a web interface but not a lot.

    I think I'll shoot for a cheaper 24 port switch to replace the dell and if I still have trouble buy a second one to replace the HP.

    We do have some central file hardrives. 2 1 terabyte drives that are only for data but they are only used by one department for large sign files. I have them connected directly to the main switches.
     
  7. Flyboy

    Flyboy Pre-takeoff checklist

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    The port links totaly drop.
     
  8. Flyboy

    Flyboy Pre-takeoff checklist

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    The Dell is a switch but it is really cheap. I think it sold for less than 30 bucks and they threw it in with a pc we bought at my old company. (we merged) I had actually retired it but had to bring it back out when we maxed out the system they already had here.

    I also think it's causing the problems but was just thinking replaceing bothe of them would be good because they are both at least 5 years old and the HP has been sitting on a table with its cooling fan blocked since it's underneath it. (Ihaven't been able to talk them in to buying a rack) :mad:

    I won't mention the rats nest of wiring they paid for... oops.. I did....:goofy:
     
  9. TMetzinger

    TMetzinger Final Approach

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    In that case, I think getting a new switch should fix the problem, and it doesn't have to be expensive.
     
  10. jesse

    jesse Touchdown! Greaser!

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    Could be a bad switch. If the port links drop totally (look and see if the ethernet light on your PC is lit up) if that light is not lit up it's most likely a bad switch.

    If windows is just saying it lost the network connection--it may have just lost contact with the DHCP server (this will cause a similar error).

    So:

    1.) If the ethernet light on all the PC's go off when this happens--bad switch.

    2.) If they stay on it's probably a crappy cable somewhere or it could still be a bad switch.


    It's good practice to replace all the network wiring when replacing the hardware. It's cheap and it's good insurance against problems like this.
     
  11. jason

    jason Administrator Management Council Member PoA Supporter

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    It could be that you've introduced a network loop somewhere. If you've created one somewhere in the chain it could be that you're causing packet storms in your network. Check to make sure that you're not connecting any switches to one another in multiple places. For low end switches each switch can only be connected to another switch through a single port. If, for instance, you go "switch 1 -> switch 2 -> switch 3 -> switch 1" bad things will happen unless your switch supports the spanning tree protocol.

    STP is another feature that you get with a higher end switch. If I were you I'd buy a Dell 3448 (48 port fully managed switch). They're cheap and they're actually really good switches for the price. I'd put them on par with with low to mid tier cisco's feature for feature. If you know you'll never ever need things like VLANs or QOS, then a lower end switch should work just fine. I'm just a fan of leaving my options open. With a managed switch troubleshooting things like this becomes much easier.

    EDIT: I mistyped the model...so I fixed it and added a link.
     
    Last edited: Feb 9, 2007
  12. mikea

    mikea Touchdown! Greaser! Gone West

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    Good advice. See if the drops occur when a given cable is connected. Try them one at a time.

    I would think even without a collision light, you would see a loop as a dramatic change in the activity light.
     
  13. Flyboy

    Flyboy Pre-takeoff checklist

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    Unfortunatly cheap is relative. To the owners here, that would be expensive.

    I don't ever see needing vlans or QOS here. So I'll stick with the cheap seats.
     
  14. gkainz

    gkainz Final Approach

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  15. jason

    jason Administrator Management Council Member PoA Supporter

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  16. Flyboy

    Flyboy Pre-takeoff checklist

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    Thanks for all the help. I spected out a netgear 24 port switch for 160 and change from CDW and the purchasing agent found a 24 port linksys without the fiber optic connections (which we probably will never need) for around 100 at a local office depot. So, Im way up in the nose bleeds :D

    lol
     
  17. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    What Tim said. Way back, I had a friend who asked my advice on network architecture. He had one hub and one switch. I gave him what I thought was good advice: Put all of the high-bandwidth stuff on the switch, and put the low-bandwidth stuff like printers, etc. on the hub.

    While that would be sound advice, this switch was sooooo god-awful slow that he found his network was actually faster when he swapped the two units. Even though there were plenty of collisions on the hub, it actually turned out to be faster because the switch was such a piece of garbage.

    Later on, he hired me to upgrade his entire network to Gigabit, one of the first such networks in Milwaukee (the spec was approved while we were working on the project). That involved the installation of a MUCH nicer switch, which worked as expected.

    So, now that I've made a short story long (I seem to be altogether too good at that), the point is that a crappy switch can be worse than simply having a hub and letting all the devices on your network fight it out. DO NOT go too cheap. :no: