It works for me on the following config:
- KVM/QEMU @ session mode
- VirtIO NIC @ NAT forward
- Linux VMs
The change applies without restarting VMs.
> virsh dumpxml openwrt1 | xmllint --xpath /domain/devices/interface -
<interface type="bridge">
<mac address="52:54:00:8b:73:59"/>
<source bridge="virbr0"/>
<target dev="tap0"/>
<model type="virtio"/>
<link state="up"/>
<alias name="net0"/>
<address type="pci" domain="0x0000" bus="0x00" slot="0x09" function="0x0"/>
</interface>
> sudo virsh net-dumpxml default
<network>
<name>default</name>
<uuid>7ef14652-23b3-4bf8-a46e-03c40ebac980</uuid>
<forward mode='nat'>
<nat>
<port start='1024' end='65535'/>
</nat>
</forward>
<bridge name='virbr0' stp='on' delay='0'/>
<mac address='52:54:00:4d:b1:00'/>
<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>
I guess this requires additional troubleshooting to isolate the issue.