Thanks for the tips. All those items checked out. After a bit more troubleshooting involving a nearby switch and my VLAN routing, things are working a little more consistently, so I'm going to chalk this up to a routing issue elsewhere in my network. I'm just not used to a NIC turning off the link light if there's not a valid route.

Re: (https://www.asrockrack.com/general/productdetail.asp?Model=X570D4U-2L2T)

Just spitballing here, but has anyone else used this ASRock mobo (with Intel X550-AT2 and i210 NICs) with xcp-ng 8.3? I've been experiencing a variety of seemingly incongruous NIC connectivity problems. All the ports seem to function normally under a standard PopOS install, so doesn't seem like a hardware failure, but I can't rule that out.

Unfortunately, due to the nature of the issue I can't provide any logs. I'm not well versed in the xcp-ng network subsystem, but one of the more consistent issues was SSH connections timing out after about a minute when connected via one vlan to one of the X550 ports but perfectly stable SSH connections when connected to a different vlan on the other X550 port.

The other head-scratcher is the 1Gb ports becoming active only intermittently after various reboots. I know this sounds like a hardware failure, but I thought I'd throw this up here just in case anyone has had a similar experience.

Thanks!