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Wireless Networks Thread, Linking two switches via fibre in Technical; Hello All, Our shiny new arts/drama building is (almost...) ready to move in to. We have a chunk of 8-strand ...
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    dhicks's Avatar
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    Linking two switches via fibre

    Hello All,

    Our shiny new arts/drama building is (almost...) ready to move in to. We have a chunk of 8-strand pre-terminated fibre cable running underground in a conduit from a cabinet in my office to a cabinet in the new building. The cabinet in my office contains a fibre patch panel and one HP ProCurve 1800-24G switch with two J4858C mini-GBIC adapters fitted. The cabinet in the new building contains another fibre patch panel and a Dell 2748 with four 0U3650 mini-GBIC adapters fitted.

    The eight strands of fibre in the pre-terminated fibre cable are all different colours, and each individual strand is attached to its own port on the patch panel in the same order at each end. The first two colours at each end are white and black respectively. The first two ports on the patch panel (same both ends) are then connected via a two-strand patch cable to the mini-GBIC of the switch.

    I get no network traffic. No little blinking activity lights for those two ports, nothing. I can log in to the web-based management console for the HP ProCurve and see that it seems to recognise that ports 23 and 24 ("dual personality" ports) have GBIC adapters in them as they are listed as type "1000BASE-SX", but other than that there seems to be no indication that either switch is doing anything.

    What have I missed? Is there some chicken-waving exercise that I need to do before a switch agrees to route traffic over fibre? Have I connected the fibre up wrongly in some way (although surely I would have noticed if a patch lead on GBIC adapter had the wrong connector?)? Have I used the wrong diameter of patch lead, and does that make all that much difference? Is my fibre bust? How do I find out if it is?

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    David Hicks

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    DMcCoy's Avatar
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    Quote Originally Posted by dhicks View Post
    Hello All,

    Our shiny new arts/drama building is (almost...) ready to move in to. We have a chunk of 8-strand pre-terminated fibre cable running underground in a conduit from a cabinet in my office to a cabinet in the new building. The cabinet in my office contains a fibre patch panel and one HP ProCurve 1800-24G switch with two J4858C mini-GBIC adapters fitted. The cabinet in the new building contains another fibre patch panel and a Dell 2748 with four 0U3650 mini-GBIC adapters fitted.

    The eight strands of fibre in the pre-terminated fibre cable are all different colours, and each individual strand is attached to its own port on the patch panel in the same order at each end. The first two colours at each end are white and black respectively. The first two ports on the patch panel (same both ends) are then connected via a two-strand patch cable to the mini-GBIC of the switch.

    I get no network traffic. No little blinking activity lights for those two ports, nothing. I can log in to the web-based management console for the HP ProCurve and see that it seems to recognise that ports 23 and 24 ("dual personality" ports) have GBIC adapters in them as they are listed as type "1000BASE-SX", but other than that there seems to be no indication that either switch is doing anything.

    What have I missed? Is there some chicken-waving exercise that I need to do before a switch agrees to route traffic over fibre? Have I connected the fibre up wrongly in some way (although surely I would have noticed if a patch lead on GBIC adapter had the wrong connector?)? Have I used the wrong diameter of patch lead, and does that make all that much difference? Is my fibre bust? How do I find out if it is?

    --
    David Hicks
    Are you using ST or LC patch panel?

    Things to remember, with LC at both ends, you have to switch a pair with a patch cable, LCs are usually clipped together and ST are easy.

    It may be doing this:


    HP Gbic TX F1(w) --------------F1(w) HP Gbic TX
    HP Gbic RX F2(b) ---------------F2(b) HP Gbic RX

    TX to TX isn't going to get you very far

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    dhicks (2nd September 2008)

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    I take it you tried switching the tx and rx cables.

    Some 3com switches we use have the GBIC ports switched off by default, and won't run if there is something plugged into the actual port 23,24

    If a torch can get light through it'll probably work (I recommend you check the decibel reading though if you want it to work properly)

    Incorrect patch leads may cause some light loss, but probably won't be a show stopper unless a long run. the cable will be marked with either 50/125micron of 62.5/125 micron make sure patch leads are same as the cable.

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    dhicks (2nd September 2008)

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    meastaugh1's Avatar
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    Is it possible that you've got both GBICs transmitting over the same strand, and therefore both switches are receiving nothing? What are the connection types on the patch panel, ST? Perhaps, you could try swapping the two connectors on the patch panel at one end.

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    dhicks (2nd September 2008)

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    Quote Originally Posted by DMcCoy View Post
    Are you using ST or LC patch panel?
    We're using ST patch panels. The pre-terminated fibre seems to be attached to the patch panel nicely, all seems securely-attached in both patch panels. The mini-GBICs in both switches use LC connectors so we are using fibre patch cables with two ST connectors at one end and an LC "double" connector at the other.

    Things to remember, with LC at both ends, you have to switch a pair with a patch cable
    I've tried swapping the two cable strands around at one end (just swapped the ST-terminated ends of the patch cable around), still no luck.

    --
    David Hicks

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    Quote Originally Posted by CyberNerd View Post
    I take it you tried switching the tx and rx cables.
    Yep, although I'll give it another go tomorrow just to make sure.

    Some 3com switches we use have the GBIC ports switched off by default, and won't run if there is something plugged into the actual port 23,24
    There's no copper cable plugged in port 23/24, the GBIC modules are installed and seem to be registered by the switches, but I can't find anything in either switch's settings that says "turn on GBIC".

    If a torch can get light through it'll probably work
    I'll get my trusty assistant to give me a hand tomorrow and we'll have a go at the give-us-a-yell-when-you-see-it experiment.

    the cable will be marked with either 50/125micron of 62.5/125 micron
    I'll check.

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    David Hicks

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    Quote Originally Posted by dhicks View Post
    Our shiny new arts/drama building is (almost...) ready to move in to. We have a chunk of 8-strand pre-terminated fibre cable running underground in a conduit from a cabinet in my office to a cabinet in the new building. The cabinet in my office contains a fibre patch panel and one HP ProCurve 1800-24G switch with two J4858C mini-GBIC adapters fitted. The cabinet in the new building contains another fibre patch panel and a Dell 2748 with four 0U3650 mini-GBIC adapters fitted.
    I have just googled the U3650 part for the Dell and unless I am mistaken this is a 1000BASE-LX where the laser is a wavelength of 1310nm. The HP modules are as you say 1000BASE-SX which operate at a wavelength of 850nm. If this true then the two fibre modules won't even see each other.

    The eight strands of fibre in the pre-terminated fibre cable are all different colours, and each individual strand is attached to its own port on the patch panel in the same order at each end. The first two colours at each end are white and black respectively. The first two ports on the patch panel (same both ends) are then connected via a two-strand patch cable to the mini-GBIC of the switch.
    Apart from checking the two fibre modules I would also do as someone else has suggested. Shine a torch down each fibre to ensure that you have both ends in the same order.

    Steve Atkinson.

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    dhicks (3rd September 2008)

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    If one is indeed LX be careful that the modules are definatly disconnected before looking down the fiber as the LX signal is damaging to your eyes and can be invisible (to human eyes), the SX is not to bad in that respect.

    To see the light safely you can use a cellphone cammera which will pick up both the visible and the infrared signals without burning out your retinas. If you are checking visible signals and are concerned about your eyes you can also just sine the patch lead on a bit of paper or non reflective surface to detect the optical signal safely.

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    How have you configured the switches if they are configurable set them at 1000 Full Duplex for both ends.

    You could also try one of the hp mini gbics in the dell.

    Ben

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    Quote Originally Posted by sjatkn View Post
    I have just googled the U3650 part for the Dell and unless I am mistaken this is a 1000BASE-LX where the laser is a wavelength of 1310nm. The HP modules are as you say 1000BASE-SX which operate at a wavelength of 850nm. If this true then the two fibre modules won't even see each other.
    Ah ha! Yes, that seems to be it exactly. Cue Mutly-style muttering "...sufchwusin mthfscn idaspe Dell sales department...". Right: me and the trusty assistant did a quick swap of the Dell and HP switches again, and now the Dell 2724 in my office is talking to the Dell 2748 in the new building. Hooray. We seem to have the worlds flakiest network connection - bang the server cabinet and either the copper connection to the main server room goes down or the fibre connection to the new building goes down.

    Right, next problem... No, no, hang on... As I was typing the problem out I realised what the solution was - change the subnet of my machine so I can see the IP address of the new switch...

    --
    David Hicks

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    Quote Originally Posted by dhicks View Post
    I realised what the solution was - change the subnet of my machine so I can see the IP address of the new switch...
    ...No, spoke too soon, that can't be it, otherwise I wouldn't be able to see the other switches, wouldn't I?..

    Okay, new problem: My workstation is connected directly to the switch that is connected by fibre to the new building (not for any drastically technical reason, you understand, it's just that I'm the IT technician so naturally the loudly-humming switch has to go in my office). Initially, my workstation is assigned an IP address via DHCP (something like 10.0.10.254) with a mask of 255.0.0.0.

    Each of our switches has been put in to "managed" mode (cheap switches, so that means their embedded web servers) and given a static IP address in the range 10.0.0.7x. I can get to switches 10.0.0.70, 71 and 73 just fine (10.0.0.73 is the one in my office, by the way). From my machine, I can't get to 10.0.0.72, though.

    I set the IP address of my machine to a static address (10.0.0.5 with mask 255.0.0.0) and I can get to 10.0.0.7x just fine. I can get to 10.0.0.72 from the gateway machine at 10.0.0.1, too. What gives?

    Is there some kind of routing issue happening here - does something, on some device, need flushing, or do I just need to wait until everything twigs where the new switch is? Have I set the wrong mask (but if that were the case I wouldn't be able to see 10.0.0.71 or 10.0.0.73, surely)?

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    David Hicks

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    the cable will be marked with either 50/125micron of 62.5/125 micron
    I'll check.
    Seemingly the fibre between the buildings is 62.5/125 micron, but somehow I've wound up with patch cables marked as "9/125". Is that bad?

    --
    David Hicks

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    Quote Originally Posted by dhicks View Post
    Seemingly the fibre between the buildings is 62.5/125 micron, but somehow I've wound up with patch cables marked as "9/125". Is that bad?

    --
    David Hicks
    Yeap, that could totally be causing issues as there will be huge signal loss between those two massively different diameter cable cores, more importantly your multimode signal won't even go through that cable:
    YouTube - What do the fiber terms 9/125, 50/125 and 62.5/125 refer to?

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    Quote Originally Posted by dhicks View Post
    Seemingly the fibre between the buildings is 62.5/125 micron, but somehow I've wound up with patch cables marked as "9/125". Is that bad?

    --
    David Hicks
    yes. 9/125 is a single mode cable.
    get some 62.5/125 patch leads

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    dhicks (4th September 2008)

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    Quote Originally Posted by SYNACK View Post
    Yeap, that could totally be causing issues as there will be huge signal loss between those two massively different diameter cable cores, more importantly your multimode signal won't even go through that cable:
    Thanks, sounds like it explains the problem. 62.5/125 patch cables are on the way. Just trying to figure out how we ever wound up with 9/125 cables now...

    --
    David Hicks

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