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Wireless Networks Thread, Connecting a new switch in via fibre in Technical; Morning my fellow heroes of EduGeek... I'm afraid I come crawling for assistance again as I am feeling thoroughly stumped ...
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    sonofsanta's Avatar
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    Unhappy Connecting a new switch in via fibre

    Morning my fellow heroes of EduGeek... I'm afraid I come crawling for assistance again as I am feeling thoroughly stumped at this juncture.

    I've bought a load of 3Com 2928-HPWR switches to let us plug in some PoE WAPs, and I'm trying to connect the switches to the network via fibre uplinks. For whatever reason, though, the switches utterly refuse to actually connect to the network

    I know all the physical gear is ok - after many combinations of SFP transceivers, patch cables and other switches - and the only common link is the new switch(es). Somewhere in the configuration (I imagine) is something that is stopping the fibre uplink from working properly.

    As I look at the switch back in my main server room (that this fibre run goes to) - if I plug the SFP module I'm using into any of my current switches, the port shows up as active on said server room switch and everything is dandy. As soon as I plug the fibre module into the new switch, it shows as inactive. I've compared and contrasted settings across the different (but all 3Com) switches and everything seems the same. The manual is no use whatsoever. The switch is otherwise working (transmitting power, I am logged into it via web interface on a laptop). Just something, somewhere, is stopping the switches actually talking to each other. It lights up this end on the new switch, but never flashes for activity, and the other end never lights up at all.

    This is getting excessively frustrating now, it's starting to take the somewhat. So I beg of you fellow geekers - any advice? Any clues? Anything incredibly obvious I have so far missed?

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    smadison's Avatar
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    A couple of questions; Have you got VLANS set-up and have you checked the configuration for the fibre ports?

    That is where i would start.

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    sonofsanta's Avatar
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    Quote Originally Posted by smadison View Post
    A couple of questions; Have you got VLANS set-up and have you checked the configuration for the fibre ports?

    That is where i would start.
    No, no VLANs. And looking at the configuration of the relevant port, it's set up the same way as fibre ports on other switches that are working fine.

    I was wondering if the main switch in my server room didn't trust the new switch or something similar, but I can't see any options on it to do with anything along those lines (3Com Switch 5500G-EI 24-Port)

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    EduTech's Avatar
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    It does sound like the fibre module is not activated in some kind of way, maybe the config is correct but do you have to activate it? I'm just speaking out loud here as i dont have any 3com Kit to even look at so i am not sure what kind of config you have available to you.

    I wouldn't of thought they would be "incompatible" in any kind of way, as at the end fo the day as long as the fibre module and link is connected correctly it should just work as you say.

    Might be worth just running through the config again just seeing what it is you have done and just double check...

    James.

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    Are you using Pukka 3com tranceivers.

    HP Procurve kit only works with HP tranceivers, maybe 3com is the same.

    Have you tried linking two of the new switches with fibre?

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    smadison's Avatar
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    How about checking connectivity?

    1) Check the transceiver on the 3Com switch. A good way to check this is connecting the TX cable end to the RX port on the transceiver, obtaining a loop on the cable. If there's link, the fiber and transceiver are ok. Repeat this procedure on the other switch.
    2) Check if the speed and duplex on both sides are the same
    3) Check the proprietary features on the other switch.

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    sonofsanta's Avatar
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    Quote Originally Posted by K.C.Leblanc View Post
    Are you using Pukka 3com tranceivers.

    HP Procurve kit only works with HP tranceivers, maybe 3com is the same.

    Have you tried linking two of the new switches with fibre?
    Genuine 3Com SFPs, right kind, they are listed as compatible parts on the 3com site and they are the same as all the other transceivers that are lying around.

    Don't have any cable lying around to directly connect two switches, sadly - if I get desperate enough I will lug one of the new switches up to the server room and try connecting them directly through all the fibre patches etc.

    Quote Originally Posted by smadison View Post
    How about checking connectivity?

    1) Check the transceiver on the 3Com switch. A good way to check this is connecting the TX cable end to the RX port on the transceiver, obtaining a loop on the cable. If there's link, the fiber and transceiver are ok. Repeat this procedure on the other switch.
    2) Check if the speed and duplex on both sides are the same
    3) Check the proprietary features on the other switch.
    Transceiver is fine, as I can plug other (working) transceivers into this switch, and it doesn't work, and the transceiver I'm using in the new switch works fine in other switches. For the same reason I know there's no strange port configuration I need to set up on the 5500G in the server room - I can swap transceivers about happily and the old switches connect on port 28 of the 5500G, whilst the new switch refuses to connect on any of the 4 SFP ports on the 5500G.



    I've pulled out the diagnostic info for this port from the switch, pasted below:
    GigabitEthernet1/0/25 current state: UP
    IP Packet Frame Type: PKTFMT_ETHNT_2, Hardware Address: 0024-7386-67df
    Description: GigabitEthernet1/0/25 Interface
    Loopback is not set
    Media type is optical fiber, Port hardware type is 1000_BASE_SX_SFP
    1000Mbps-speed mode, full-duplex mode
    Link speed type is force link, link duplex type is force link
    Flow-control is not enabled
    The Maximum Frame Length is 10240
    Broadcast MAX-ratio: 100%
    Unicast MAX-ratio: 100%
    Multicast MAX-ratio: 100%
    PVID: 1
    Port link-type: access
    Tagged VLAN ID : none
    Untagged VLAN ID : 1
    Port priority: 0
    Peak value of input: 1 bytes/sec, at 2010-02-15 12:56:03
    Peak value of output: 158 bytes/sec, at 2000-04-26 12:38:26
    Last 300 seconds input: 0 packets/sec 0 bytes/sec 0%
    Last 300 seconds output: 0 packets/sec 117 bytes/sec 0%
    Input (total): 7 packets, 476 bytes
    4 unicasts, 0 broadcasts, 3 multicasts
    Input (normal): 7 packets, 476 bytes
    4 unicasts, 0 broadcasts, 3 multicasts
    Input: 0 input errors, 0 runts, 0 giants, 0 throttles
    0 CRC, 0 frame, 0 overruns, 0 aborts
    0 ignored, 0 parity errors
    Output (total): 3216 packets, 490849 bytes
    8 unicasts, 808 broadcasts, 2400 multicasts, 0 pauses
    Output (normal): 3216 packets, 490849 bytes
    8 unicasts, 808 broadcasts, 2400 multicasts, 0 pauses
    Output: 0 output errors, 0 underruns, 0 buffer failures
    0 aborts, 0 deferred, 0 collisions, 0 late collisions
    0 lost carrier, 0 no carrier

    It's picking up that it's got fibre plugged in; the only thing that makes me pause is its insistence on referring to port 25 as GigabitEthernet1/0/25 when it's not ethernet at all, but there's no setting I've found that implies that means anything other than just being a convention (as every port is labelled this way).

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    sonofsanta's Avatar
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    3 STUFFING HOURS


    Right - thank you for all your help - eventually I managed to dredge up the one relevant post in the 3Com forums - turns out that even though I am using all 3Com switches, all 3Com transceivers etc. etc. the stupid sodding thing can't auto-set the speed and duplex. Manually setting the speed to 1000mbps and the duplex to full, on both switches, fixes the problem.


    VERY ANGRY YET ALSO RELIEVED NOW. Kind of like pooping yourself in public after a week of constipation I guess.

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    smadison's Avatar
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    Glad you got it sorted

  10. Thanks to smadison from:

    sonofsanta (15th February 2010)

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    EduTech's Avatar
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    Good Stuff, Glad you sorted it.. i've ever used 3com switches so my post was just a question out the hat so to speak.. but will remember that just incase it pops up in future

    James.

  12. Thanks to EduTech from:

    sonofsanta (15th February 2010)

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    sonofsanta's Avatar
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    I'm just relieved it turned out to be 3Com being stupid and not me, so I can continue bluffing my way through this job and keeping everyone convinced I actually know what I'm doing most of the time

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    machin05's Avatar
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    Quote Originally Posted by sonofsanta View Post
    Kind of like pooping yourself in public after a week of constipation I guess.
    That's genius!

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    Quote Originally Posted by sonofsanta View Post


    3 STUFFING HOURS


    Right - thank you for all your help - eventually I managed to dredge up the one relevant post in the 3Com forums - turns out that even though I am using all 3Com switches, all 3Com transceivers etc. etc. the stupid sodding thing can't auto-set the speed and duplex. Manually setting the speed to 1000mbps and the duplex to full, on both switches, fixes the problem.


    VERY ANGRY YET ALSO RELIEVED NOW. Kind of like pooping yourself in public after a week of constipation I guess.
    I've had this problem more than once with HP and D-Link gear talking to each other. Unless the fibre port is set at 1000mbps it wouldn't always connect.

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    It re-enforces what we were told in Cisco school, "always hard code the speed and duplex unless you need auto!!" And yes it's caught me out too!

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    sonofsanta's Avatar
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    Quote Originally Posted by garrya100 View Post
    It re-enforces what we were told in Cisco school, "always hard code the speed and duplex unless you need auto!!" And yes it's caught me out too!
    Aye; working with computers as I do, I should know better than anyone not to rely on them in any way!

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