As pointed out by Alex, starting the dnsmasq service makes the libvirt network to crash and not start.
So I found a work-around for this: you must set the option "bind-interfaces" in the "/etc/dnsmasq.conf" file to tell the dnsmasq daemon to bind itself to the interface specified in the config file.
As pointed out by Alex, starting the dnsmasq service makes the libvirt network to crash and not start.
So I found a work-around for this: you must set the option "bind-interfaces" in the "/etc/dnsmasq.conf" file to tell the dnsmasq daemon to bind itself to the interface specified in the config file.
This solved the problem for me.