I have about 400 pi units and some of them have developed a peculiar issue. The eth0 interface appears to be up, but I can't seem to pull a DHCP address. When I set a static IP, it shows in the ifconfig output, but the interface can't ping anything. I've looked at the dmesg output, but nothing stands out. Is there a diagnostic I can run to verify that the network interface is functioning properly?
These units are all using a POE hat module. Most of the units seem fine, but this issue has started to appear on about a dozen units so far. Any help is appreciated.