As mentioned by others, this at first look appears to be Spanning Tree (ST) related. Since you are observing the issue at end of day fairly consistently, I would put the following things on my investigation list:
- Look for networking devices plugged into a power strip that someone is turning off at the end of the day when they leave. Look especially for devices installed in user workspaces to add additional ports, authorized or not. For example a small user installed switch that unknowingly has a low bridge priority value (making it high priority to become the ST Root Bridge). The user installed switch may become the root bridge when the person arrives early for the day, but few others are there to notice the interruption, but when they leave early and power off their networking device, the network has to negotiate a new root again and disrupts the other workers still there.
- Look for people that might be unplugging a device temporarily, like cleaning crews.
- Look for networking devices that have redundant power supplies and diversified power sources. One power source may be interrupted and the device might not rolling cleanly between power supplies causing it to reinitialize. Again this power interruption may be caused by a power strip being turned off or a plug being pulled.
Some food for thought,
Alan Emery
IBM Global Solution Center
Coppell, TX
ademery@xxxxxxxxxx
