Cannot start network interfaces

Good day all, I have having an issue starting virtual networks defined within libvirt: virsh # net-start cmdb error: Failed to start network cmdb error: internal error: Child process (VIR_BRIDGE_NAME=virbr3 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/cmdb.conf -- leasefile-ro --dhcp-script=/usr/lib/libvirt/libvirt_leaseshelper) unexpected exit status 2: dnsmasq: failed to create listening socket for 172.26.80.1: Address already in use The definition of the network is pretty simple: virsh # net-dumpxml cmdb <network> <name>cmdb</name> <uuid>42ffd3c4-624d-46ad-be21-bb3c61c67e41</uuid> <bridge name='virbr3' stp='on' delay='0'/> <mac address='52:54:00:5b:e9:6c'/> <domain name='shihad.org'/> <ip address='172.26.80.1' netmask='255.255.255.0'> </ip> </network> At the OS level, this network interface should get created by libvirt, so I am a bit mystified why dnsmasq is having an issue starting, as there is nothing using this address yet. In fact, virbr3 does not exist until libvirt would bring up this interface: ifconfig -a | grep virbr virbr0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 I am running libvirt 9.0.0 on Debian 12. Any help or pointers greatly appreciated. Thanks! Iain