Ubuntu/VBox Network Bridge Script

#!/bin/bash
cmd="$1";
[ -z "$cmd" ] && cmd="start";
case "$cmd" in
        start)
                brctl addbr br0;
                brctl stp br0 on;
                brctl addif br0 eth0;
                (ifdown eth0 1>/dev/null 2>&1;);
                ifconfig eth0 0.0.0.0 up;
                ifconfig br0 192.168.0.80 netmask 255.255.255.0 up;
                route add default gw 192.168.0.1;
                for file in br0 eth0;
                do
                        echo "1" > /proc/sys/net/ipv4/conf/${file}/proxy_arp;
                        echo "1" > /proc/sys/net/ipv4/conf/${file}/forwarding;
                done;
                echo "1" > /proc/sys/net/ipv4/ip_forward;
                ;;
        stop)
                brctl delif br0 eth0;
                ifconfig br0 down;
                brctl delbr br0;
                ifup eth0;
                ;;
        restart,reload)
                $0 stop;
                sleep 3;
                $0 start;
                ;;
esac;