[SOLVED] Network interfaces no longer come up automatically

[abayliss]

I'm having a strange problem with one of my PVE hosts where the network interfaces are no longer starting automatically. The machine is a Dell T20 with one onboard NIC, and I have a bridge interface configured for my VMs with just that NIC as a member. Yesterday after turning the machine back on after being away, the network was completely down, and I eventually traced this to the NIC interface, eno1, showing as down in ip link, and ethtool eno1 showing Link detected: no. The link lights are working, the switch at the other end says the port is up, and the Intel management interface that also uses the onboard NIC is working.

I can make everything work as normal by doing ip link set eno1 up and ifup vmbr0 at which point ethtool reports Link detected: yes. If I then reboot the interface still doesn't come back up and I have to go through the same process.

Everything was working before I turned the machine off on Friday, I did do an upgrade mid-last week which took me up to kernel 5.4, but everything worked after the reboot for that.

I can't see anything strange in dmesg (attached), so I'm at a loss as to how to investigate this. It's literally as if the cable is unplugged, but it isn't.

Spoiler: /etc/network/interfaces

auto lo
iface lo inet loopback

iface eno1 inet manual

auto vmbr0
iface vmbr0 inet static
    address 10.0.0.25/24
    gateway 10.0.0.1
    bridge-ports eno1
    bridge-stp off
    bridge-fd 0
    bridge-vlan-aware yes
    bridge-vids 2-4094
    #pre-up ip link set eno1 up
    post-up ethtool -K eno1 gso off gro off tso off

auto vmbr1
iface vmbr1 inet static
    address 172.16.0.1/24
    bridge-ports none
    bridge-stp off
    bridge-fd 0
#Host Only

 

[Moayad]

Hi,

Please post output of status networking after booting

systemctl status networking.service

 

[abayliss]

Hah! You've pointed me in the right direction to fix it, along with some further digging I'd been doing. I realised that as part of the upgrade I did the other day, I also upgraded from ifupdown to ifupdown2, and I'm in the habit of doing an apt purge of removed packages (maybe a bad idea). Looking at the status of networking.service it said

root@pve-01:~# systemctl status networking.service
● networking.service - Network initialization
   Loaded: loaded (/lib/systemd/system/networking.service; disabled; vendor preset: enabled)
   Active: inactive (dead)
     Docs: man:interfaces(5)
           man:ifup(8)
           man:ifdown(8)

so enabling that service seems to have fixed the problem after a reboot. I suspect what happened is that the purge of ifupdown disabled networking.service.

 

[Moayad]

Hi,

great! that you solved your issue by yourself, Please mark the thread as 'SOLVED' Thanks!

 

[kvamsi.k143]

My observation on this issue is with UEFI settings. Doesn't work with UEFI boot. NICs are isolated with UEFI.

 

[Pr0c]

I just want to say THANK YOU for posting this as I had the exact same issue!