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Wireless Networks Thread, Some computers have "no network access" in Technical; Hello, Recently I cannot seem to ping ~ half of our computers (yes they are on! :P), which also brings ...
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    Some computers have "no network access"

    Hello,

    Recently I cannot seem to ping ~ half of our computers (yes they are on! :P), which also brings with it the fact they cannot print or access the internet.

    Now when I'm pinging one of our switches I'm not getting consistent results, one set of pings will give me a 10ms response, while another set will give me upwards of ~400ms whilst pinging another switch will always give me ~4 - 10ms ping every time.

    Made even harder by the fact that when these were installed the guys didn't bother to label any of the ports

    Any suggestions?

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    Michael's Avatar
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    That doesn't sound right at all. You should get 1ms or close to within a LAN. Have you tried rebooting the switch(es)? Do you have any VLANs setup? Have you tried resetting to factory default and if necessary upgrading the firmware?

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    RinSewand's Avatar
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    Are the machines all on the same switch or different ones?

    What does their ipconfig report? Are they getting a DHCP address? Are they set to the wrong static address...

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    BatchFile's Avatar
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    LAN storm? or has some eejit looped a cable?

    Check your switches - are any of them going mad?

    Edit:
    Nobody's running a ghost multicast are they? that can wipe out whole chunks of network (especially wireless APs)
    Last edited by BatchFile; 30th March 2010 at 02:41 PM. Reason: Just thought of another

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    nephilim's Avatar
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    I would tend to agree with the looped cable...has happened ALOT here with the old tech. Had to rip out the switches and start from scratch (ended up having several U's available in my cabinets)

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    Thanks for the suggestions guys.

    I rebooted them both after managing to get to them and everything seems to be working fine now apart from the pings...

    When I ping -t the offending switch I can see it slowly rise to nearly 800ms and then back down to around 9ms over about 6 seconds (even did this when I was plugged directly into port 1 on the switch... weird).

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    Quote Originally Posted by Blue_Cookeh View Post
    When I ping -t the offending switch I can see it slowly rise to nearly 800ms and then back down to around 9ms over about 6 seconds (even did this when I was plugged directly into port 1 on the switch... weird).
    What sort of switch is it?

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    It's a Netgear FS726TP

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    Quote Originally Posted by Blue_Cookeh View Post
    It's a Netgear
    That explains everything.

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    BatchFile's Avatar
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    Is it possible to isolate that switch (disconnect the uplink) without bringing the network crashing down? if so, try it, see if the ping time returns to normal. If it does, I'm going for a loop.

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    Quote Originally Posted by K.C.Leblanc View Post
    That explains everything.
    Ha! I didn't pick it, im innocent I swear!

    Quote Originally Posted by TonyRidal View Post
    Is it possible to isolate that switch (disconnect the uplink) without bringing the network crashing down? if so, try it, see if the ping time returns to normal. If it does, I'm going for a loop.
    Will give it a go.

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    powdarrmonkey's Avatar
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    Quote Originally Posted by K.C.Leblanc View Post
    That explains everything.
    I don't see why. I've only had one problem with Netgear's pro range, and it didn't affect link quality. If you've had a bad experience, do please be less vague.

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    Batman's Avatar
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    I had trouble imaging a bunch of laptops that had Marvell Yukon ethernet on them using a 48 port netgear switch. It worked fine with a 3com we had lying around, but we pinned that down to a configuration problem. We had to increase the max packet size on something somewhere and then it all worked. It turned out not to be the switch that was at fault.

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    I haven't been able to get at the switches yet, but I ran Wireshark and when it happens I'm getting results from two different computers, with the broadcast address as the destination.

    The protocol is NBNS and the Info says "Name query NB M41N.ATH.CX<00>"

    Any ideas?

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    Michael's Avatar
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    I would try and reset the switch to factory default to wipe any configuration settings. If there was a loop it would affect the whole network, not just one switch.

    If resetting to factory default and isolating the switch makes no difference I would contact Netgear themselves for a replacement.

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