I experienced a very odd issue this morning that I can't explain. I'm hoping that someone has some ideas of what I can check to see what actually happened.
Here's the scenario: Early this morning I noticed one of my servers couldn't connect to another server on the same VLAN. While I was investigating I noticed that all of the sudden all of my servers were having connectivity problems. When I say connectivity problems, I mean total network connectivity problems -- couldn't even ping them. There were a few servers that seemed to be unaffected but the majority of them went offline. My first thoughts were to check for high CPU utilization on the core switches (redundant 4507R's) -- nothing to see there. No log entries about any problems, no OSPF recalculations or HSRP failovers. Next, I started to look at the connectivity between devices (core-distribution) -- there wasn't anything to see there either; no large bursts of packets, no interfaces down, etc.
The solution, appeared to be restarted one particular server. Once that server restarted, everything started coming back online. When I look at that servers interfaces though, I don't see any traffic anomalies.
Does anyone have any ideas on what I can look at, from the switch side, to help me diagnose this?
Many thanks in advance,