networking - Part of LAN network connected to 1 switch freezes up periodically

I'm managing an office network which is spread across 2 buildings. (see network setup below)

In building 2, we are getting a problem where the network slows down and then completely cuts off. The only way to bring it back is to power cycle the switch, then before it slows down again, go into the GUI dashboard and power cycle it from the dashboard.

The issue has happened 4 times (and is becoming more frequent). It first happened 2 weeks ago, then again yesterday, and twice today.

I'm trying to work out what could be causing it. I've believe I've narrowed it down the switch as the only network devices in building 2 are the switch and the WiFi access point. When the switch is down, the WiFi access point is still running.

When building 2 is down, if i go to building 1, I can still connect to the network fine.

Any idea what might be causing the above? My 2 guesses are:

1. network storm - but this would be odd as we haven't recently added notable new devices to the network. So why has it come about all of a sudden, plus why is it getting worse on each reset?




2. faulty switch (needs replacing under warranty)

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Network is configured as follows :

Building 1

• Draytek 2860 router (connected to fibre modem)


• Netgear 24 gigabit port smart switch


• Ubiquity UAP wifi access point (mostly used by mobiles / tablets.. low traffic)



• 4 wired LAN computers (heavier use, as we all use dropbox on LAN sync mode for heavy files)


• printers and other devices


• all cabling cat6

Building 2 (connected to building 1 by cat6 c. 30m cable length)

• Netgear 48 gigabit port smart switch (Netgear GS748T)


• Ubiquity UAP wifi access point (used mostly by 2 laptops, heavier usage that building 1, again most traffic is used from dropbox LAN sync.)