wrong mtu after upgrade to 9

T

Tobbe

Member
Oct 4, 2021
22
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i recently upgraded my 4 mode proxmox cluster from 8 to 9.
after a while i ran into some odd problems and after some troubleshooting it turns out the interface of one node did not get the correct mtu applied (i got one network with jumbo frames)
resulting in one node with mtu of 1500 and the rest 9000

looking at the system log an greping for mtu i have one line:
/usr/sbin/ifup[1386]: warning: error while writing to file /sys/class/net/enp3s0f0/mtu: [Errno 2] No such file or directory: '/sys/class/net/enp3s0f0/mtu'

it turns out this interface is now called ens6f0 and not enp3s0f0 and proxmox was able to realize the names had changed and applied all other things except for the updated mtu.
this is why i didn't realize the problem at first.

so looks like something in proxmox when it applies the network settings related to mtu is not aware of the alternate interface names.

to me this looks like a bug.
the fix for me is easy, i can just edit /etc/network/interfaces and change the interface name and reboot
 
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if new kernel have changed interface name, the mtu from /etc/network/interfaces can't applied, as it's still defined on old name interface.
(thanks systemd for the name change after each kernel update)

pve9 have the new network interface pining to avoid this problem.
 
spirit said:
if new kernel have changed interface name, the mtu from /etc/network/interfaces can't applied, as it's still defined on old name interface.
(thanks systemd for the name change after each kernel update)

pve9 have the new network interface pining to avoid this problem.
Click to expand...
It might still be interesting to see the /etc/network/interfaces. ifupdown2 in PVE has been patched to support altnames, so there might be a bug (depending on how the MTU is set in the ifupdown2 configuration).
 
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