Wifi Traffic can't traverse a fiber link between two SG300 switches

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  • Updated 4 years ago
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I have a very strange problem.  I've got two Cisco SG300 switches in two buildings with a fiber link of about 100' between them.  In the building where the firewall and internet connection reside we have no problem with WiFi connectivity and throughput, but on the far side of the fiber link wireless clients connect to their APs but have very unstable and intermittent internet access.  The problem is not just with Aerohive APs but with Sophos AP50's I have there as well.

I thought I had the issue resolved by implementing a VLAN and assigning an Aerohive SSID and local DHCP server to it, but it worked for only a couple of hours and then started exhibiting the same behavior - fine in the building on the firewall/internet side but no good on the far side of the fiber link.

And now for the final piece - none of the wired clients on the far side of the fiber link have any trouble at all.  I'm wondering what there could be about the packets coming out of the APs onto the wired network that is different from the packets from wired clients and switches and causing the connection to fail going from one SG300 to the other across the fiber run.

If anyone has experienced anything like this or has a suggestion as to how to try to diagnose/resolve it I would be grateful to hear from you.

Thanks,

Steve
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Steve Kellogg

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Posted 4 years ago

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Eastman Rivai, Official Rep

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Steve,

Have you tested the traffic from the access point? You may login to the AP and run ping to a device on the other site. If the result is good, you may need to check the radio health on the AP. 
"show acsp neighbour" command should give you some information. If the ping result is not good you may need to check if there are any configurations on the switch port that may cause this. You may need to run debug on the switch in order to analyse further.
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Steve Kellogg

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Thanks for your reply.  In the meantime I've discovered that the SG300-28 has disabled each port that an AH AP is connected to.  Across the fiber link in another building all the AP's are working fine connected to an SG300-52.  I can't tell what's different between the AP and switch configuration in the two buildings to cause all the AP ports in one room to be disabled.
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Eastman Rivai, Official Rep

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You may need to check if any port security configured on the ports. The best way in order to find the cause of the issue is to run debug on the switch.