Much safer to use a TAP device statically allocated with tunctl.

contrib/bochs/ifup.tun

-#!/bin/sh
-
-SCRIPT=$0
-INTERFACE=$1
-
-if [ `id -u` != 0 ]; then
-    echo ""
-    echo "Enter root password for configuring network interface $INTERFACE"
-    echo "(To avoid this prompt, make the script $SCRIPT setuid-root)"
-    /bin/su -c "$SCRIPT $INTERFACE" || exit 1
-    exit 0
-fi
-
-/sbin/ifconfig $INTERFACE 10.254.254.2 netmask 255.255.255.252
-
-# Force dhcpd to notice the new network interface
-if [ -x /etc/init.d/dhcpd ]; then
-  /etc/init.d/dhcpd reload # Redhat
-elif [ -x /etc/init.d/dhcp ]; then
-  /etc/init.d/dhcp restart # Debian
-fi