Situation
Upon upgrading from PVE 7.4 (Debian 11) to PVE 8.0 (Debian 12), the On-Board Realtek NIC stops functioning correctly. The NIC may work upon boot, but connectivity will stop within minutes and the console begins outputting lines similar to the text below —r8169 0000:01:00.0 enp1s0: rtl_ephyar_cond == 1 (loop: 100, delay: 10).
My Environment
Manufacturer: Dell Inc.
Product Name: OptiPlex 3060
Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)
Solution
#Add the non-free reponano /ect/apt/sources.list
deb http://ftp.debian.org/debian bookworm-updates main contrib non-free
# Run apt update, install the package, and reboot.
apt update
apt install r8168-dkms -y
reboot now
This worked well for me. Your mileage may vary.
Other Solution - Don't use Realtek NICs.