here is a bad trip i had i want to share.
I changed the 48 ports switch i use in my production stack (i had PoE, not needed, swapped with a non-PoE).
I did not remember immediatly that the replaced switch had jumbo frames (MTU 9000) enabled, and i did not check the new one. All my vsphere virtual switchs have a 9000 MTU.
The nigth next to replacement, every job failed with an NFC error can not get next FILE_MESSAGE or so, crashing at "getting info from vsphere" point.
Everything else was functionning (browsing VM, recalculate size,etc).
Once i enabled jumbo frames on the switch, every thing went fine.
Additional not : i first tried to set the MTU to 1500 on the management virtual switch of a vSphere, and it turned ugly : i can't anymore connect by ssl or gui, and now i have to choose between restore default vsphere config or perform a full reinstall.
The network restore config options failed.