I have computers with Intel and Realtek Ethernet cards, and I keep forgetting to install the linux-firmware packages when I put Debian on them. I can see messages in syslog telling me that the firmware for the card could not be found, but, surprisingly, I can access the network just fine.
Why is this? I was under the impression that firmware was necessary for normal operation of any device. Could I run into more problems with the firmware than without? I've been having some issues with random disconnects with a Broadcom Ethernet card (using the tg3 driver) and I read a post about issues caused by buggy firmware.