Network debugging for guests

When a guest has no network, debug the path in layers: domain XML, libvirt network XML, host bridge state, and packet flow.

Guest has no address

Start with the libvirt view and then compare it with what the guest thinks.

virsh domiflist vm01
virsh domifaddr vm01
virsh net-dhcp-leases default

If the network is NAT-backed and DHCP never issued a lease, look for dnsmasq startup failures in the relevant journal.

Bridge mismatch

If the domain XML references br0 but the host only has virbr0, the guest definition is wrong for the current host.

virsh dumpxml vm01 | less
ip link show type bridge
bridge link

Host policy problems

Firewall, NetworkManager, or systemd-networkd can override assumptions about the bridge or forwarding behavior.

Follow the packet path

Use this habit instead of guessing:

1. Confirm the guest interface in domain XML.
2. Confirm the network definition or host bridge exists.
3. Confirm the host sees traffic on the expected bridge.
4. Confirm routing or NAT rules exist for the intended path.