connect the user mode network stack to VLAN 'n', configure its
DHCP server and enabled optional services
-net tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h][,vhostforce=on|off]
- connect the host TAP network interface to VLAN 'n'
+ connect the host TAP network interface to VLAN 'n'
use network scripts 'file' (default=/etc/qemu-ifup)
to configure it and 'dfile' (default=/etc/qemu-ifdown)
to deconfigure it