With an upgrade to 12.1 (from an early 11) -- the em(4) gigabit wired ethernet drive (on PCI) does not seem to preserve the link status across suspend/resume cycles on various Intel and Dell laptops.
- default 12.1 minimal install.
- connect no ethernet cable.
- boot (em0 will be up by default)
- 'sudo ifconfig em0 down'
- suspend by closing lid or 'zzz'.
- resume 5 mins later,
- observe that em0 is back up.