Need Help - virt-manager can't use 'default' NAT network

InitDeny · May 17, 2025, 3:13pm

Subject: : libvirt default Network State Mismatch and Autostart Issues on Arch Linux

Hi everyone,

I’m struggling to set up a virtual machine using virt-manager on Arch Linux with libvirt 11.3.0, and I’d really appreciate some help. Here’s a summary of my journey so far:

System Details

OS: Arch Linux
libvirt: 11.3.0
Network Manager: netctl (configured a bridge at /etc/netctl/bridge)
Wi-Fi Interface: wlan0 (doesn’t support 4-address mode, so switched to NAT networking)
Goal: Install a VM using virt-manager with the default NAT network.

Timeline of Issues and Steps

Initial Setup:
- Enabled KVM (sudo modprobe kvm-intel kvm), created a netctl bridge (/etc/netctl/bridge), and started/enabled libvirtd.
- Tried to start a VM in virt-manager with a bridge network, but got: Unable to add bridge wlan0 port vnet0: Operation not supported.
- Confirmed via iw list that wlan0 doesn’t support 4-address mode (Supported interface modes: IBSS, managed).
- Switched to NAT networking using the default network.

NAT Network Failure:

Attempted to start the VM with the default NAT network, but got: Unable to complete install: 'Requested operation is not valid: network 'default' is not active'.
Found that the default network didn’t exist:
```
virsh net-list --all  # Showed nothing
```

Defined the default network using:

virsh net-define /dev/stdin <<EOF
<network>
  <name>default</name>
  <bridge name="virbr0" stp="on" delay="0"/>
  <forward mode="nat"/>
  <ip address="192.168.122.1" netmask="255.255.255.0">
    <dhcp>
      <range start="192.168.122.2" end="192.168.122.254"/>
    </dhcp>
  </ip>
</network>
EOF

Firewall Issues:
- Tried to start the default network:
```
sudo virsh net-start default
```
  - Got errors:
    - error: error creating bridge interface virbr0: Operation not permitted
    - error: internal error: firewalld can't find the 'libvirt' zone that should have been installed with libvirt
- Confirmed firewalld was running and the libvirt zone was missing:
```
sudo firewall-cmd --get-active-zones  # Only showed public (wlan0)
```
- Tried to create the libvirt zone:
```
sudo firewall-cmd --permanent --new-zone=libvirt
```
  - Failed with Error: NAME_CONFLICT: new_zone(): 'libvirt'.
- Found libvirt is a built-in zone:
```
sudo firewall-cmd --permanent --delete-zone=libvirt
# Error: BUILTIN_ZONE: 'libvirt' is built-in zone
```

Service Restarts:

Stopped and restarted services to reinitialize the libvirt zone:

sudo systemctl stop libvirtd.socket libvirtd-ro.socket libvirtd-admin.socket
sudo systemctl stop libvirtd
sudo systemctl stop firewalld
sudo systemctl start firewalld
sudo systemctl start libvirtd

Successfully started the default network:

sudo virsh net-start default
# Network default started

Confirmed virbr0 was created:

ip link show
# 9: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> ...

State Mismatch and Autostart Issues:

Immediately after starting, virsh net-list --all showed:

Name      State      Autostart   Persistent
----------------------------------------------
default   inactive   no          yes

Tried to start again:

sudo virsh net-start default
# error: Requested operation is not valid: network is already active

But virsh net-list --all still showed inactive. virbr0 remained in ip link show.

Tried to enable autostart:

sudo virsh net-autostart default
# Network default marked as autostarted

But it didn’t persist:

virsh net-list --all
# Name      State      Autostart   Persistent
# ----------------------------------------------
# default   inactive   no          yes

Logs were missing:

cat /var/log/libvirt/libvirtd.log
# cat: /var/log/libvirt/libvirtd.log: No such file or directory

Current State

The default network is in a weird state: libvirt says it’s inactive, but trying to start it says it’s already active, and virbr0 exists.
Autostart doesn’t stick, possibly a permissions issue.
Logs are missing, so I can’t debug further. I suspect journald might have the logs, but I haven’t checked yet.

Questions

Why is there a state mismatch between virsh net-list --all (inactive) and the actual state (already active)?
Why isn’t autostart persisting despite sudo virsh net-autostart default succeeding?
Where are libvirtd logs on Arch Linux if /var/log/libvirt/libvirtd.log doesn’t exist?
How can I get the VM installation working in virt-manager?

Any help would be greatly appreciated I’m stuck and would love to get this VM running! Thanks in advance.

PS: I’ll be AFK for the next few hours but will get back to this as soon as possible. Thanks for any help in the meantime!

InitDeny · May 20, 2025, 6:30am

Hey all, quick bump - I’m done banging my head against the wall .
What other virtual managers do you folks use on EndeavourOS?
I just want to mess around with a macOS Monterey USB bootable in a VM.

On my Mac, I tried

VirtualBox (simple but buggy)
Parallels (decent but paywalled)
and another one I can’t recall (better quality, trickier to use).

USB passthrough was a nightmare, though NAT/bridge mode worked fine - ironic, since Linux should have less restrictive drivers!
Any recs for a Mac-friendly VM setup that plays nice with USB and networking?

ricklinux · May 21, 2025, 9:15pm

Did you skim through the wiki?

https://discovery.endeavouros.com/applications/how-to-install-virt-manager-complete-edition/2021/09/

Personally I use vmware workstation pro.

ajgringo619 · May 21, 2025, 9:47pm

Never needed to create a bridged network. One thing that I’ve always done on my systems is switch to the home zone in firewalld before installing/configuring libvirtd.

His_Turdness · March 20, 2026, 12:43am

Sorry for necroposting, but I ran into the same issue as the OP. Nothing seemed to work. But when I removed the “default” (virbr0) connection and created a new one which I named “br0”, the NAT network for the VM worked.

I haven’t tested bridged networking yet and probably will not, since I’m only using a windows VM to download a software update for my car.