I don't know for sure that this is just related to ACPI sleep or if it happens randomly as well, but my wired NIC has trouble where it will lose its address, saying it is 0.0.0.0, say concurrently that it had no carrier, and then take out all the switches near it. I didn't think to get a pcap, but I'd note all switches three hops out from the thing blinking madly on all ports. Not yet having the culprit identified, we moved things yesterday so that the Thinkpad ended up being one switch closer to the central switch in the cellar, and it knocked out most of the network in the house, rather than just my office. I'm not sure how best to debug this. I can't have the thing loose on my network, but I can construct a DMZ and let it live in that for data collection. Before I dive into that, though, I'd love to get a list of data that would be maximally useful for me to collect. The system in question is a Thinkpad T420, and the NIC is an Intel 82579LM. It's running updated FreeBSD 12-RELEASE.
Random note, running if_em_updated.ko as noted various places has my NIC performing normally after waking. I haven't let it run long enough on my network to be confident that the issue won't return, and it's unclear what this implies even if I don't see the issue return, but it's a data point.
I'm going to close this, as it's a duplicate of: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=231828 *** This bug has been marked as a duplicate of bug 231828 ***