Proxmox Ethernet Failing After Upgrade

Proxmox Ethernet Failing After an Upgrade

After up­grad­ing my pair of Lenovo M720q ma­chines from Proxmox VE 8 to 9, they ran­domly started drop­ping their con­nec­tion to the in­ter­net. The only so­lu­tion that seemed to fix it was to phys­i­cally dis­con­nect, then re­con­nect their Ethernet ca­bles. Weird, right?

I am hon­estly not sure why this was hap­pen­ing, but I can of­fer a per­ma­nent so­lu­tion in case you (or any­one else) en­coun­ters this same prob­lem.

The Solution

First, find the la­bel for the phys­i­cal Ethernet adapter for your sys­tem:

ip addr

For me, it was eno1. The lo­cal ad­dress of your sys­tem might be bound to a vir­tual adapter (like vmbr0). This is NOT what we are in­ter­ested in. We are in­ter­ested in the phys­i­cal adapter.

Next, dis­able TSO for the live sys­tem. Substitute eno1 for what­ever you just found for the la­bel of your Ethernet adapter.

ethtool -K eno1 tso off

To make this set­ting per­ma­nent, add a line to ex­e­cute this on sys­tem boot to your /etc/network/interfaces/ file.

iface eno1 inet manual
    post-up ethtool -K eno1 tso off

Your Mileage May Vary

If you have this prob­lem, this fix might work for you, and it might not. Ei­ther way, good luck!