When I created bond0, it set itself to autostart. That matches my experience from PVE 8.
However, it also autostarts the bonded NICs, and I can't disable that so long as bond0 exists. In PVE 7 and 8, the actual bonded ports were not set to autostart.
In PVE 9, it just ignores any attempt to disable the autostart on the underlying NICs.
It makes sense to me that if a bond autostarts, the underlying NICs/interfaces should as well, but since this is changed behavior from my previous experience, I wanted to confirm that nothing odd is happening.
In case something odd is happening above, I've included my config below. Please let me know if you see something odd. (I wasn't sure if I needed to set the MTU at the physical interface, the bond, or the bridge, so I did them all.
Bash:
root@andromeda1:~# uname -a
Linux andromeda1 6.17.4-2-pve #1 SMP PREEMPT_DYNAMIC PMX 6.17.4-2 (2025-12-19T07:49Z) x86_64 GNU/Linux
root@andromeda1:~# pveversion -v
proxmox-ve: 9.1.0 (running kernel: 6.17.4-2-pve)
pve-manager: 9.1.4 (running version: 9.1.4/5ac30304265fbd8e)
proxmox-kernel-helper: 9.0.4
proxmox-kernel-6.17.4-2-pve-signed: 6.17.4-2
proxmox-kernel-6.17: 6.17.4-2
root@andromeda1:~# cat /etc/network/interfaces
# network interface settings; autogenerated
# Please do NOT modify this file directly, unless you know what
# you're doing.
#
# If you want to manage parts of the network configuration manually,
# please utilize the 'source' or 'source-directory' directives to do
# so.
# PVE will preserve these directives, but will NOT read its network
# configuration from sourced files, so do not attempt to move any of
# the PVE managed interfaces into external files!
auto lo
iface lo inet loopback
iface nic0 inet manual
#On-Board Intel 1 Gbps NIC
iface nic1 inet manual
#Intel X550 10 GbE - Port 1
iface nic2 inet manual
#Intel X550 10 GbE - Port 2
auto nic3
iface nic3 inet manual
mtu 9000
#Mellanox Connect-X4 10 GbE - Port 1 - MTU 9000
auto nic4
iface nic4 inet manual
mtu 9000
#Mellanox Connect-X4 10 GbE - Port 2 - MTU 9000
auto bond0
iface bond0 inet manual
bond-slaves nic3 nic4
bond-miimon 100
bond-mode 802.3ad
bond-xmit-hash-policy layer2+3
mtu 9000
#Mellanox Connect-X4 Bonded Ports - MTU 9000
auto vmbr0
iface vmbr0 inet static
address 10.10.6.2/24
gateway 10.10.6.1
bridge-ports nic0
bridge-stp off
bridge-fd 0
#Management and Cluster Network
auto vmbr1
iface vmbr1 inet manual
bridge-ports bond0
bridge-stp off
bridge-fd 0
bridge-vlan-aware yes
bridge-vids 2-4094
mtu 9000
#Primary High-Speed Interface - MTU 9000