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Wireless Networks Thread, Topologies/Switch Throughput in Technical; Hi Folks, Without being too invasive, could anyone shed a little light into their network topology? We're having some issues ...
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    synaesthesia's Avatar
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    Topologies/Switch Throughput

    Hi Folks,

    Without being too invasive, could anyone shed a little light into their network topology?

    We're having some issues which we're struggling to narrow down - since we had a loopback (2 switches lost their trunking config and caused one hell of a loopback - typical that it lost the trunk config but not the loopback detection you have to disable when you set up a trunk!) we've had major network slowdowns and all the stations only connect at 100Mb as opposed to a gig.

    All switches are Dlink 1210-24 units with power saving and broadcast storm control disabled. Every morning, when PC's start up they get 100Mbit connections. Switch uplinks still have a gig - this seems to occur if stations are turned off for a long time (i.e. overnight) as it doesn't seem to happen at lunchtimes. This doesn't happen to all switches, just a few.

    If we force 1000Mbit rather than autonegotiation they work at full speed, however this naturally breaks WOL so is a non solution. Dlink are helping as much as they can but they're also drawing blanks.

    I'm not convinced it's a switch issue however I'm slightly concerned that maybe we're just asking far too much of such cheap switches (they were certainly better than the 3com 4400's they replaced!)

    We have 4 core switches which connect to all the edge devices, some via fibre, some via cat5/6, some trunked. A couple of them do (out of no choice) have daisy chained devices. Our first thought is exceeding the 48Gb throughput limit of the switches, however surely as there are 24 ports at 2Gb each, that wouldn't actually be possible? They're not overheating, they were fine a couple of weeks ago. We're still systematically working through changes that have been made in the last fortnight which includes a couple of fibre links, removal of some test servers, changing a couple of switches (there a couple evil Procurve devices propping important parts up currently).

    Short of investing in a decent core switch setup which is something we're looking at anyway for the future (money, money money!) any suggestions?

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    Quote Originally Posted by synaesthesia View Post
    We have 4 core switches which connect to all the edge devices, some via fibre, some via cat5/6, some trunked. A couple of them do (out of no choice) have daisy chained devices. Our first thought is exceeding the 48Gb throughput limit of the switches, however surely as there are 24 ports at 2Gb each, that wouldn't actually be possible?
    It's down to the switching capacity of the core - if your maxing out the connections into it I can almost guarantee you'll be exceeding the switching capacity unless yo have a seriously expensive piece of kit in there.

    It sounds like your running 1GB/s to desktops on a 2GB backbone?
    Quote Originally Posted by synaesthesia View Post
    Short of investing in a decent core switch setup which is something we're looking at anyway for the future (money, money money!) any suggestions?
    I'd go for a 10GB/s core and 10GB/s uplinks to your near edge switches - you will need it if your wanting a reliable and fast network and actually use that 1gb/s to the desktop.
    TBH your probably better off throttling down your desktops by putting a 100mb/s limit on each one at the edge.

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    glennda's Avatar
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    is there anything which requires gig to the desktop? bar media/music editing i can't seem much of need for it imho especially if you don't have the core to cope with it.

    I had similar issues with our Core switch which was terrible (some old nortel thing) I put in a nice shiny HP E5406zl chassis and network speed increased overnight!

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    m25man's Avatar
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    We have 4 core switches which connect to all the edge devices, some via fibre, some via cat5/6, some trunked
    How are the 4 switches connected together at the core? Do they use a a proprietary stacking mechanism?

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    Ignore that last post, I see that they are not stackable any way!
    I suspect that you are cascading these switches into a group in which case your throughput as your stating is no more than your inter connecting links.
    In which case you don't actually have anything that could be classified as a core array do you! You have a bunch of switches daisy chained is that correct?
    Do you have a schematic to show how this array connects to each other?

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    synaesthesia's Avatar
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    Grr, forums broke last night when replying to this with a nice lengthy one!
    We do have a bunch of standard managed layer 2 switches.
    Roughly:

    Say we have switch A, B, C and D as the "core"
    Switch B, C and D are all connected to A via trunks for performance & failover reasons. About 4 edge devices have other switches daisy chained as a last resort - the rest are directly connected to one of the 4 cores. (This is a very narrow idea - we have 2 sites and just concentrating on one - the problems exist over both sites which are connected via gigabit fibre)

    We have *NO* budget to play with hence why we're trying our best to make do until we can make way for something decent and even then it won't be a 10GbE.
    I do have a schematic, I'll post it up later when I'm on site if yesterdays changes haven't helped. In the last 10 days or so we've been rolling back any changes we've made - removal of test servers temporarily, removal of replacement switches (evil procurves), connection of some multimode fibre links in place of Cat6 trying to narrow down the problem. What I would like to do is disconnect the site link however that leaves one site without internet and the other without SIMS. So if all else fails we may well have to organise downtime in chunks to try and narrow down parts of the network to the problem.
    We do need gig to desktop ideally - we do a lot of media type stuff but being an aging CC3 network it is very much noticeable. We will certainly need to sort that before we go vanilla Windows 7 next year

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    synaesthesia's Avatar
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    Rough topology:



    Very rough as we're still trying to figure out exact links - most of it is leftovers from previous configurations, unhelpfully.
    It's worth noting that none of the procurves exhibit the behaviour of throttling speed. And no, we won't be replacing the "core" with them - it's the Procurves that murdered the network last time round!

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    SYNACK's Avatar
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    Eeeeeeep, frackadee, D-Link are shocking. I know we had two sites based mostly (apart from the core) on 1248T gigabit switches. V1 and V2 both of which we have had to scrap thanks to ports simply dropping off the network untill the power was pulled and reset on them.

    If you have any procurves give them responcibility for the core as you will have a much better chance of the network surviving.

    We had one (d-link) that overheated and kept wiping the config. First off enable STP on everything that can take it and even enable the broadcast control (as long as it does not keep resetting itself each week).

    I would also look long and hard at your cabling if it is dropping to 100mbit, could be bad wireing which a decent cable tester (borrow one) is likely to show you. It coule also be power saving features which I'd personally just turn off. You need that limited CPU power for more important things like holding on to the config.

    One thing that helped us for six months or so was updating the switch firmware which kept them stablish for a little longer.

    We even had a D-Links managment features just sompletely burn out, it still worked as a dumb switch but no ip, no STP or anything like that. The chip inside just died.

    All of the above leads me to recoment leaving the importand jobs to any other switchs that you have access to. If not try to mitigate config wipes by putting STP on all ports so it can defend against stuff ups. Drop the link aggregation for now as the amount of chunking the switches are probably inflicting on the trunks anyway is not likely to be giving you that much more performance than a single link and it puts a lot of load on the switches which can't cope in some instances. If some are stable you can leave the trunks to them but isolate the dodgey ones with STP on all ports and have no trunks.

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    Same as what @SYNACK has said, the DLinks are what are probably causing the issue rather then the procurves - we had strange issues here with some Nortel switches not liking the Procurves very much and causing errors on the procurves - the nortels said everything was find the procurve's picked up errors from the data from the nortels. Once all the nortels where removed and replaced with Procurves (and i think we have 2 netgears but 30 something procurves) ever since that the network has run so smoothly!

    Although i did mange to tombstone the core switch when trying to setup a LACP trunk to a Netgear Fiber Switch

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    Quote Originally Posted by SYNACK View Post
    Eeeeeeep, frackadee, D-Link are shocking. I know we had two sites based mostly (apart from the core) on 1248T gigabit switches. V1 and V2 both of which we have had to scrap thanks to ports simply dropping off the network untill the power was pulled and reset on them.

    If you have any procurves give them responcibility for the core as you will have a much better chance of the network surviving.

    We had one (d-link) that overheated and kept wiping the config. First off enable STP on everything that can take it and even enable the broadcast control (as long as it does not keep resetting itself each week).

    I would also look long and hard at your cabling if it is dropping to 100mbit, could be bad wireing which a decent cable tester (borrow one) is likely to show you. It coule also be power saving features which I'd personally just turn off. You need that limited CPU power for more important things like holding on to the config.

    One thing that helped us for six months or so was updating the switch firmware which kept them stablish for a little longer.

    We even had a D-Links managment features just sompletely burn out, it still worked as a dumb switch but no ip, no STP or anything like that. The chip inside just died.

    All of the above leads me to recoment leaving the importand jobs to any other switchs that you have access to. If not try to mitigate config wipes by putting STP on all ports so it can defend against stuff ups. Drop the link aggregation for now as the amount of chunking the switches are probably inflicting on the trunks anyway is not likely to be giving you that much more performance than a single link and it puts a lot of load on the switches which can't cope in some instances. If some are stable you can leave the trunks to them but isolate the dodgey ones with STP on all ports and have no trunks.
    Had similar issues with D-Link at my last place. Replaced them all with lovely Juniper switches

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    synaesthesia's Avatar
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    It was the procurves failing BIGtime that caused us to buy in the dlinks in the first place. We've replaced a few of them on the HP lifetime warranty but are only using them on an as-needed basis. We're about to swap out the main core switch for one of hte procurves until we get a decent coreswitch.
    Will keep an eye.

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    Just for refference the ones we brought lasted quite well for 2.5-3.5 years, just long enough for a false sence of security to set in then the started dieing slowly one by one. It was a very easy trap for us to fall into as everything looked fine till we were in too deep and they attempted to drown us with faults.

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    Quote Originally Posted by SYNACK View Post
    Just for refference the ones we brought lasted quite well for 2.5-3.5 years, just long enough for a false sence of security to set in then the started dieing slowly one by one. It was a very easy trap for us to fall into as everything looked fine till we were in too deep and they attempted to drown us with faults.
    +1 All of our D-Link kit started failing just outside of its 3 year warranty (about 6 months in the job for me!). We had 30% failure rates within 6 months of that. I've sworn never to buy another D-Link product (consumer or business!) because of it.

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    localzuk's Avatar
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    Similar experience with D-Links here at my last school. Core switch just decided to start wiping various bits of information, disabling ports etc... As it was just out of warranty, we replaced everything with HP and they've had zero network issues for 4 years now.

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    Isolate an affected switch from the rest of the network, and remove all cables bar one to test. Does it still drop to 100?

    Remove all trunks from the network. This could be done if there is 2 of you, 1 at each end of the link, ready set pull the trunk and plug 1 cable into a free port. Does it still drop to 100?

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