Another test that you could try to see if it's your switch is start a ping from Host A to the switch and start another ping from Host A through the switch to another device. If the ping through the switch to the other device never stops, your management interface on the switch could be having an issue (it's virtual, so it could just be the switch itself). If the ping through the switch never stops, then you're port is obviously still up.
If both stop responding, then you could have a problem with the host that you're ping from. It could be having problems with cabling, bad port on the switch, or a bad nic, but you'll know it's definitely losing connection to the network at that point.
HTH,
John
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