I suspect the issue might be somewhere in your udev configuration.
You can get the evaluated udev rules by running 'udevadm test <device path>'
So running 'udevadm test /sys/class/net/ens6f2' and 'udevadm test /sys/class/net/eth0' and comparing outputs should tell you/everyone else whats different for those devices and why they use different naming schemes.
The old ethX names depend on the order of initialization and is therefore unstable.
The new format (e.g. ens6f2) depends on pci device numbers and is stable.
Cheers,
Valentin
> eth0: Policy *slot* yields "ens6f0".
> eth0: Could not set AlternativeName= or apply AlternativeNamesPolicy=,
> ignoring: File exists eth0:
> /usr/lib/udev/rules.d/80-net-setup-link.rules:11 NAME 'ens6f0' eth0:
> /usr/lib/udev/rules.d/99-systemd.rules:68 RUN '/lib/systemd/systemd-sysctl
> --prefix=/net/ipv4/conf/$name --prefix=/net/ipv4/neigh/$name
> --prefix=/net/ipv6/conf/$name --prefix=/net/ipv6/neigh/$name' eth0:
> sd-device: Created db file '/run/udev/data/n69' for
> '/devices/pci0000:00/0000:00:1c.0/0000:01:00.0/net/eth0' ens6f0: Failed to
> rename network interface 69 from 'eth0' to 'ens6f0': File exists
It looks like your BIOS is reporting the same PCIe Slot for both your igb and Broadcom network cards.
I assume one of your Broadcom network interfaces is already named ens6f0.
In fact., this might be a BIOS issue...
whats the output of `sudo dmidecode -t9`?
Best solution for you is probably to set all or some network interface names manually, see https://wiki.debian.org/NetworkInterfaceNames#CUSTOM_SCHEMES_USING_.LINK_FILES
Cheers,
Valentin