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So, it's Saturday night and I'm at work, so that's a bad start. I've got one Windows 7 PC out of 25 that's having a network problem. It can connect to the Internet fine (I'm typing this on it as I speak) but it can only intermittently see the Samba file share we use in the office. If I change the port this PC is connected to on the switch, the situation reverses - I can access the share perfectly but the Internet connection stops working.

I've turned off the Windows firewall, and that's not helped. I've tried different IP addresses and workgroups, all to no avail. I've tried different network cables - no joy. I've been through about ten ports on the switch but they either allow Internet or share access.

Earlier today this PC was connected to a small switch with four others that could access the Internet and the share just fine, even though they were all using the same port back at the "main" switch.

Even stranger still is that when the problem occurred earlier in the day I swapped out the PC for a brand new one and it continued having the same problem!

I get a feeling that this is a problem with some obscure fix that simply hasn't occurred to me, and someone out there will be able to help.


Edit

Okay, I've "fixed" it by swapping out the master switch for a different one and now it works fine.

I'd still appreciate knowing what could have caused the problem, though, as with my (fairly limited, admittedly) knowledge of how a network works this simply shouldn't have been possible.

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  • What does your network topology look like? Cisco, Juniper, or cheap stuff? Can you check the DCHP scope for all addresses assigned, or DNS for errors? – Austin T French Mar 29 '14 at 22:08
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I feel your weekend pain, especially with a problem that should be simple.

I would first clear out the machine's ARP cache: netsh interface ip delete arpcache Then I would clear the same machine's DNS cache: Ipconfig /flushdns You can also remove the network device entry in device manager. Be sure to reboot.

If there is the possibility of shutting down the switch and restarting, I would do that too, then let's see where we are.

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  • Thanks Dave - I did flush the caches and the device manager entry, but that didn't help. I should have rebooted the router before I replaced it, but then I'd have to check all the other PCs to make sure the problem hadn't just moved to some other user. – Grim... Mar 29 '14 at 21:17
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"I'd still appreciate knowing what could have caused the problem, though, as with my (fairly limited, admittedly) knowledge of how a network works this simply shouldn't have been possible."

Either the switch is defective or there are ARP cache problems between the computer or switch or both. Really nothing impossible. I see stuff like this all the time.

I didn't want to ask you to replace the switch..just yet.

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