No internet in VMs or LXC containers.

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buba

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Oct 20, 2025
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I have a Dell Optiplex 3020 proxmox server with VMs and LXC containers. Some LXC containers have network connectivity without issue but when I create new containers they cannot reach my network or the internet. That happends wether IP is static or DHCP.

Working internet and network:

Code: 
root@proxmox:~# cat /etc/pve/lxc/100.conf
arch: amd64
cores: 1
features: nesting=1
hostname: wireguard
memory: 512
nameserver: 1.1.1.1
net0: name=eth0,bridge=vmbr0,gw=192.168.10.1,hwaddr=BC:24:11:DB:6C:85,ip=192.168.10.9/24,type=veth
onboot: 1
ostype: debian
rootfs: local-lvm:vm-100-disk-0,size=8G
searchdomain: home
swap: 512
unprivileged: 1
Non working internet and network:

Code: 
root@proxmox:~# cat /etc/pve/lxc/104.conf
arch: amd64
cmode: shell
cores: 1
hostname: Technitium
memory: 512
net0: name=eth0,bridge=vmbr0,gw=192.168.10.1,host-managed=1,hwaddr=BC:24:11:0C:A8:34,ip=192.168.10.12/24,type=veth
ostype: fedora
rootfs: local-lvm:vm-104-disk-0,size=8G
swap: 512
unprivileged: 1
Host managed or not, doesn't make a difference.

Proxmox's network config:

Code: 
root@proxmox:~# 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

auto nic0
iface nic0 inet manual

auto vmbr0
iface vmbr0 inet static
       address 192.168.10.6/24
       gateway 192.168.10.1
       bridge-ports nic0
       bridge-stp off
       bridge-fd 0
       bridge-vlan-aware yes
       bridge-vids 2-4094

source /etc/network/interfaces.d/*
I have reinstalled proxmox because of this issue and it also happens on the fresh install. please help me and please tell me what I am doing wrong.
I'll add that VLANS also don't work on containers, even with the "working" network.
I created a new VM and tried to install Debian 12 on it. Now eve the VMs don't detect network. DHCP configuration failed in the setup.
 
Hello buba, as you noticed, the issue is not that Proxmox “doesn’t detect” the network.

You have vmbr0 set as VLAN-aware with:
bridge-vids 2-4094
Click to expand...
You didn’t mention whether you are using a managed switch or how the physical switch port is configured.

If the switch port connected to nic0 is not configured as a trunk/tagged port, and your VMs/LXC are not explicitly VLAN-tagged, the traffic will be dropped and you won’t see any connectivity.

So either:
  • allow VLAN 1 on the bridge, or
  • explicitly tag your VMs/LXC and make sure the physical switch port is configured accordingly.
 
nico1875p said:
Hello buba, as you noticed, the issue is not that Proxmox “doesn’t detect” the network.

You have vmbr0 set as VLAN-aware with:

You didn’t mention whether you are using a managed switch or how the physical switch port is configured.

If the switch port connected to nic0 is not configured as a trunk/tagged port, and your VMs/LXC are not explicitly VLAN-tagged, the traffic will be dropped and you won’t see any connectivity.

So either:
  • allow VLAN 1 on the bridge, or
  • explicitly tag your VMs/LXC and make sure the physical switch port is configured accordingly.
Click to expand...
I have a dumb TP-Link switch connected. I thought it should pass on the tagged traffic and leave the untagged traffic alone. the tp-link is connected to an edgerouter x sfp acting as vlan aware switch. that port is vlan 1 untagged and 20,30 tagged. Proxmox doesn't let me set vlans from 1-4094, says limit is from 2-4094. and explicitly tagging CTs and VMs with VLAN 1 does nothing.
 
nico1875p said:
Hello buba, as you noticed, the issue is not that Proxmox “doesn’t detect” the network.

You have vmbr0 set as VLAN-aware with:

You didn’t mention whether you are using a managed switch or how the physical switch port is configured.

If the switch port connected to nic0 is not configured as a trunk/tagged port, and your VMs/LXC are not explicitly VLAN-tagged, the traffic will be dropped and you won’t see any connectivity.

So either:
  • allow VLAN 1 on the bridge, or
  • explicitly tag your VMs/LXC and make sure the physical switch port is configured accordingly.
Click to expand...
Also, I removed the VLAN aware configuration completly, untagged the TEST CT I was using but still am getting Network Unreachable errors.
 
“I thought it should pass on the tagged traffic and leave the untagged traffic alone”
Click to expand...

What you are describing is the behavior of a hybrid or access port on a managed switch, not of a dumb switch.
A non-managed switch does not distinguish between tagged and untagged traffic; it simply forwards Ethernet frames as-is.

To fix this, you need one of the following:

remove VLAN tagging on the EdgeRouter port and use a single untagged VLAN (no VLAN-aware bridge on Proxmox),
or
Remove the dumb switch and connect Proxmox directly to the EdgeRouter using a trunk port.
or
Replace the dumb switch with a managed switch and configure proper access / trunk / hybrid ports.

This is a physical VLAN design issue, not a Proxmox side issue.
 
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