VMs not getting DHCP response and are unaccessible

timbrook

New Member
Jan 14, 2021
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tl;dr same config on different machines, different results. How to debug?

This is all with a fresh install of 6.3 downloaded today. I've installed on a Aorus Pro AX Z490 board and am using the onboard NIC.

After install I set the net interface to DHCP

Code:
auto vmbr0
iface vmbr0 inet dhcp
    bridge-ports enp5s0
    bridge-stp off
    bridge-fd 0

I've tried setting gateways, subnets and as well a static ip. All end up with a working host that I can connect to. But the same issues as follows.

Created a VM, enable qemu, add a network card (tried all of them) and boot into a ubuntu live. This was my test, the first attempt was with win10. Fails to get an IP, but I can see broadcast traffic and my ubiquity USG sees the request for IP. And thats it, never get anything back to the VM. I think this is something to do with the NIC on the motherboard. I installed the exact same config on a 2018 mac mini and it works flawlessly.

So here's my question. What should I be looking for to debug this?? I've spent a few days on this now (part time) and can't seem to make any progress.
 

timbrook

New Member
Jan 14, 2021
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This is what I'm working with now, i'd like to go back to using dhcp if possible as well.

Code:
# 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 enp5s0
iface enp5s0 inet manual

auto vmbr0
iface vmbr0 inet static
        address 192.168.1.201
        netmask 255.255.255.0
        gateway 192.168.1.1
        bridge-ports enp5s0
        bridge-stp off
        bridge-fd 0

This is my test vm as well.
Code:
# cat /etc/pve/qemu-server/100.conf
agent: 1
boot: order=scsi0;ide2
cores: 8
ide2: local:iso/ubuntu-20.04.1-desktop-amd64.iso,media=cdrom
memory: 8096
name: virtio-test
net0: virtio=C6:91:B6:BD:4B:E9,bridge=vmbr0,firewall=1
numa: 0
ostype: l26
scsi0: local-lvm:vm-100-disk-0,size=32G
scsihw: virtio-scsi-pci
smbios1: uuid=6c44fcfc-e970-4b97-8dcd-9ac7d2a9a775
sockets: 1
vmgenid: b12576d5-d8bd-4ab0-80e5-aa8afe8344b2
 

timbrook

New Member
Jan 14, 2021
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can you ping the node from your VM?
No I never get an IP in the VM. Tried regardless and get Network unreachable as expected. Gave the VM a static IP on the same subnet and was still unable to ping. Just host unreachable.
 

cwjohnston

New Member
Jan 19, 2021
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I'm experiencing a similar issue with both containers and Qemu VMs.

With a fresh Proxmox 6.3 installation, nether Qemu VM nor LXC container will obtain an IP address via DHCP. When I manually assign an address I can ping that address from the Proxmox host, but not from other hosts on the same network segment.

My Proxmox host uses Asus TUF Gaming x570-Pro (Wifi) motherboard. Similar to the OP, my board is advertised with an Intel I225-V ethernet controller supporting 2.5gbit operation. Perhaps this is relevant to the issue?

The first two steppings or revisions of this controller have documented flaws, e.g. https://wccftech.com/intel-foxville...ng-issues-persist-z490-motherboards-affected/

In my case, lspci identifies the following:

Code:
07:00.0 Ethernet controller: Intel Corporation Device 15f3 (rev 03)

From what I've read, my board seems to be the B3 stepping (third revision of the controller) but I'm not 100% certain on this point.
 

leesteken

Famous Member
May 31, 2020
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355
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I've only seen this when a firewall is blocking packets that have no IP yet (for example the DHCP setting to NO in Firewall, Options) or when multiple (virtual) machines have the same MAC-address on the network.
 

timbrook

New Member
Jan 14, 2021
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No I never get an IP in the VM. Tried regardless and get Network unreachable as expected. Gave the VM a static IP on the same subnet and was still unable to ping. Just host unreachable.

Update on this, can now ping both ways after making sure all firewall rules are set to off (don't know how to dump that config here) and no outbound WAN traffic is possible :/
 

timbrook

New Member
Jan 14, 2021
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Fresh install and bios update on my motherboard and same behavior. Kinda wish I had a network card laying around I could try :/
 

leesteken

Famous Member
May 31, 2020
1,747
355
88
Maybe it helps if you add a MAC to the bridge interface? This way, the DHCP client is sure to send a stable MAC to the DHCP server and the firewall(s) (because of MAC filters) should not block it. (Make sure to a MAC that does not already exist on the network. The example below is probably fine.)
Code:
iface vmbr0 inet dhcp
    bridge-ports enp5s0
    bridge-stp off
    bridge-fd 0
    hwaddresss ether 52:54:56:B1:D6:E0
 

srwhite

New Member
Jan 28, 2021
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I am new to Proxmox as of a few weeks ago but stumbled across the same exact issue with my ProArt Creator Z490 boards. This appears to be a problem with the igc driver in the 5.4 kernel that Proxmox uses. I was able to fix the issue by installing a newer kernel, although I wouldn't recommend that outside of a lab environment for now.

I would be nice is an updated driver could be built into the next update, but for my lab/dev deployment I'm okay with taking the risk of a newer kernel.
 

timbrook

New Member
Jan 14, 2021
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Update, solved with the kernel upgrade. I can confirm that on the z490 series chipset the version of igc just drops packets. I didn't take the time to bisect what patch works to resolve the issue fwiw I just turned it straight to 11.
 

fets83

Member
Nov 19, 2019
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Hi, same issue here with asus B550F
This lspci output for my igp
Code:
05:00.0 Ethernet controller: Intel Corporation Device 15f3 (rev 02)
@timbrook did you install manually the kernel (given by @srwhite) or did it came with proxmox upgrade ?
When do you think it will bacome available on proxmox upgrade ?
 

marcosscriven

Member
Mar 6, 2021
93
7
8
@timbrook - I've just been tearing my hair out facing this exact issue, before trying a spare USB3 ethernet adapter, and it working fine: https://forum.proxmox.com/threads/j...t-time-i-cant-get-guest-network-access.85880/

I forgot I'd changed my motherboard since I last tried VM bridging, so assumed it was something to do with my use of Proxmox.

I have an AMD b550, but I see the z490 you mention also used the Intel i225-V NIC.

How did you find out it just 'drops packets'? I'd read it was having issues with >1gbit before, but wasn't concerned as that's what all my switches are on.
 

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