I am running Poweredge R620 servers. With Debian 10 I had no trouble, I could reliably set my network names using udev and they came up consistently even when moving from older hardware years ago. Knowing full well that upgrading to Debian 11 would break everything, I have resisted for years, but I finally gave up and started moving forward.
After fighting for the past day with a machine, I think the answer here is going to be that beginning with Debian 11 there is simply no way to reliably name the network interfaces now.
Starting with bullseye, udev is officially dead. There are still some remaining files buried on the system but /etc/udev/rules.d/70-persistent-net.rules no longer has any effect on the network interfaces.
/etc/default/grub -- "net.ifnames=0 biosdevname=0" have been removed and update-grub run
/etc/systemd/network/ -- I created the link files such as 10-eth0.link with the appropriate MAC addresses, but because the ethX names already exist, renaming is not possible:
[Match]
MACAddress=74:86:7a:ed:f6:a3
[Link]
NamePolicy=
Name=eth0
systemctl status systemd-networkd.service -- confirmed that this service is indeed active and running
Very early in dmesg I continue to see this:
[ 2.193760] tg3 0000:01:00.0 eth0: attached PHY is 5720C (10/100/1000Base-T Ethernet) (WireSpeed[1], EEE[1])
[ 2.227087] tg3 0000:01:00.1 eth1: attached PHY is 5720C (10/100/1000Base-T Ethernet) (WireSpeed[1], EEE[1])
[ 2.247850] tg3 0000:02:00.0 eth2: attached PHY is 5720C (10/100/1000Base-T Ethernet) (WireSpeed[1], EEE[1])
[ 2.263753] tg3 0000:02:00.1 eth3: attached PHY is 5720C (10/100/1000Base-T Ethernet) (WireSpeed[1], EEE[1])
The problem here is that the ethX names are being assigned backwards. The physical plugs have other brackets in the way so what I previously used as eth0 and eth1 is now being assigned to eth3 and eth2. And despite all of the above, debian and systemd refuse to ever assign "predictable" names to any of the interfaces (nothing shows up in dmesg). I ran across some info about a "BIOSdevname" setting in the actual BIOS, but can find no such setting in the last available BIOS rev for these servers. Because the system is assigning the ethX names, I am unable to reassign the correct names using the systemd link files.
The only solution I've found to work is to use the link files and assign the interface with names like dmz0, dmz1, etc. What's the deal here and what ever happened to the concept that I should be able to set up my computer the way I want to? The udev utility was 100% reliable for all the machines I've run since it was first introduced, and now we're stuck with a system that simply can't be given alternate information? Yeah I'm frustrated and annoyed.
I don't know if anyone else has run across other possible solutions, I fought with the last box for two weeks trying to name eight interfaces in the proper order and never could find anything that would work.
In my case, the server has four gigabit network ports. And I do in fact create bridges on them because nearly all of my services run on VMs (I run two identical servers for redundancy of the services, and run load balancing off the firewall). Honestly this isn't really a matter of the exact interface names, but rather why the ability to give them the desired names was intentionally broken starting with Debian 11. And as a sidebar, also trying to understand why the newer system refuses to assign the predictable names, because if it did that then I would be free to simply rename them as ethX with the systemd link files the way udev used to. On the firewall with eight network ports, yeah having to give all new names to everything was a really big deal tied to a lot of different software packages. On these servers, though, there's not much running except kvm and I only had to readdress the bridges to the new interface names and everything worked.
It's just the principle of it that REALLY bugs me...