Almost a year ago, I did setup Proxmox on an old gaming machine with 8 CPU and 16 Gb of ram.
I wish I knew earlier about Proxmox as is such a great tool that anyone doing a bit of self-hosting should consider using.
I am not going to explain what Proxmox is, or how to install.
There are many good videos on youtube that cover that in details.
Instead, what I want to dig into, is the Proxmox network interface, that did cause me some trouble.
Everything was working great, until one morning, I woke up and saw that my area was under a power outage, the laptop was off, since the battery life span is very short.
Power came back, rebooted the laptop, moved onto the desktop station, opened the browser just to get greeted by an error.
My DNS server wasn't resolving any address, that meant something went wrong.
I host my own DNS server on Proxmox, so if that is not working I can't surf the internet.
Opening Proxmox on the browser interface wasn't working.
The ping command wasn't reaching the laptop IP address.
The network was fundamentally broken.
After few minutes spent thinking, I opened the lid of my laptop and logged in.
First thing, I checked the status of the virtual machines
root@home:~# qm list
VMID NAME STATUS MEM(MB) BOOTDISK(GB) PID
100 pi-hole-recursive-dns running 4096 32.00 2179
101 Ubuntu running 4096 40.00 2369
102 kasm running 4096 65.00 2838
103 Azuracast-ubuntu-server running 4096 100.00 5242
104 ubuntu-server-searx stopped 4096 32.00 0
To my surprise the VM's were up and running but I couldn't load the Proxmox web interface on my Desktop.
Since I wasn't able to ping my laptop, I guessed that maybe just rebooting my router would fix it, but it didn't.
Now, I knew there was some issue with the Proxmox machine connecting to the router.
The router seemed to be working fine as I could ping other devices in the house but not the laptop so I started searching until I found some people saying that the problem could be etc/network/interfaces file in the Proxmox machine.
I was desperate 😁 , which led me to post my interfaces file on Reddit.
root@home:~# cat /etc/network/interfaces
#etc/network/interfaces
auto lo
iface lo inet loopback
iface enp4s0 inet manual
auto vmbr0
iface vmbr0 inet static
address 192.168.0.11/24
gateway 192.168.0.1
bridge-ports enp4s0
bridge-stp off
bridge-fd 0
iface wlp3s0 inet manual
A fellow redditor, pointed out that for some reason I was missing a line compared to his interface file.
auto enp4s0
So, I opened up /etc/network/interfaces with nano and edited the file
root@home:~#sudo nano /etc/network/interfaces
#etc/network/interfaces
auto lo
iface lo inet loopback
auto enp4s0
iface enp4s0 inet manual
auto vmbr0
iface vmbr0 inet static
address 192.168.0.11/24
gateway 192.168.0.1
bridge-ports enp4s0
bridge-stp off
bridge-fd 0
iface wlp3s0 inet manual
Rebooted the laptop and then everything went back working.
As of today, I still have no idea why that line fixed my problem.
I should probably study a bit more networking. 😁
Of course my problems didn't end there.
Few months later, my area suffered another power outage, that put me back in the same situation as few months prior, the connection between my laptop and the router was gone once again.
This time, I was confident enough that I could fix the issue the same way I did above even though that wasn't really the case. 😥
Didn't know what to do.
Went back to my old friend "stackoverflow" to find an answer but had no luck.
Luckyly Proxmox has a forum, where I opened this thread:
Losing network connection after each Proxmox reboot
Unfortunately, before anyone answered I had already found an fix.
This is what my /etc/network/interfaces looked like currently
root@home:~# cat /etc/network/interfaces
#etc/network/interfaces
auto lo
iface lo inet loopback
auto enp4s0
iface enp4s0 inet manual
auto vmbr0
iface vmbr0 inet static
address 192.168.0.11/24
gateway 192.168.0.1
bridge-ports enp4s0
bridge-stp off
bridge-fd 0
iface wlp3s0 inet manual
The /etc/network/interfaces is identical to the one from few months back.
Kept searching and it turns out that there is a command to check if there is an error in /etc/network/interfaces so I gave it a go
ifup vmbr0
error: vmbr0: bridge port enp4s0 does not exist
I finally had the culprit.
The enp4s0 witch stand for ethernet network peripheral # serial # didn't exist.
So I thought of listing all the Ethernet network interface
root@home:~# ls /sys/class/net
bonding_masters fwbr101i0 fwbr105i0 fwln102i0 fwpr100p0 fwpr103p0 tap100i0 tap103i0
enp3s0 fwbr102i0 fwln100i0 fwln103i0 fwpr101p0 fwpr105p0 tap101i0 veth105i0
fwbr100i0 fwbr103i0 fwln101i0 fwln105i0 fwpr102p0 lo tap102i0 vmbr0
or
root@home:~# hwinfo --short --network
network interface:
fwln102i0 Ethernet network interface
fwbr101i0 Ethernet network interface
fwln105i0 Ethernet network interface
fwpr101p0 Ethernet network interface
tap100i0 Ethernet network interface
fwln101i0 Ethernet network interface
tap103i0 Ethernet network interface
veth105i0 Ethernet network interface
fwbr100i0 Ethernet network interface
enp3s0 Ethernet network interface
fwpr100p0 Ethernet network interface
fwbr103i0 Ethernet network interface
fwpr103p0 Ethernet network interface
lo Loopback network interface
fwln100i0 Ethernet network interface
tap102i0 Ethernet network interface
fwln103i0 Ethernet network interface
vmbr0 Ethernet network interface
fwbr102i0 Ethernet network interface
fwpr102p0 Ethernet network interface
fwbr105i0 Ethernet network interface
tap101i0 Ethernet network interface
fwpr105p0 Ethernet network interface
As you can see there is no enp4s0 network interface but enp3s0, so all I had to do was changing the /etc/network/interfaces to point to enp3s0
root@home:~#sudo nano /etc/network/interfaces
#etc/network/interfaces
auto lo
iface lo inet loopback
auto enp3s0
iface enp3s0 inet manual
auto vmbr0
iface vmbr0 inet static
address 192.168.0.11/24
gateway 192.168.0.1
bridge-ports enp3s0
bridge-stp off
bridge-fd 0
iface wlp3s0 inet manual
Rebooted the laptop and solved the problem!
As it was pointed out by a Proxmox staff member "Stoiko Ivanov", here is the root of the issue:
This happens every now and then and is dependent on the BIOS/Motherboard and its pci-device enumeration.
(it's a result of systemd's predictable network interface names) - see e.g.:
https://forum.proxmox.com/threads/latest-systemd-udev-breaks-network-device-naming.53238
and
https://forum.proxmox.com/threads/webui-unreachable-after-adding-nvme-drive.85500
Put shortly - usually after you've fixed it it should stay stable (until the next BIOS update or major kernel update)
