ipv4

This is an init.d script I wrote some time ago that creates a virtual bridge adapter bridging two NICs. Of course you will need bridge-utils installed. To enable the script, copy the code below to a file /etc/init.d/bridge and (in debian/ubuntu) run:

update-rc.d bridge defaults

Note that it takes 30s for the bridge to become active.

#!/bin/sh
# Script to start|stop|restart bridging of two network devices
# Written by Jochen Miroll 05/28/05

ADDRESS="10.10.0.10/24"
GATEWAY="10.10.0.1"
DEV1=eth0
DEV2=eth1
#ONSTOP is the device that gets the IP address when bridging is stopped
ONSTOP=$DEV1
BR=bridge
SYSPATH=/sys/class/net
#userspace tools
BRCTL=/usr/sbin/brctl
IP=/bin/ip

#bail out if our userspace tools are not installed
test -f $BRTCL || exit 0
test -f $IP || exit 0

case "$1" in
        start)
                echo -n "Bridging $DEV1 and $DEV2: "

                if [ -d "$SYSPATH/$BR" ]; then
                        echo "$BR already exists."
                        exit 1
                fi
                if [ ! -d "$SYSPATH/$DEV1" ]; then
                        echo "$DEV1 does not exist."
                        exit 1
                fi
                if [ ! -d "$SYSPATH/$DEV2" ]; then
                        echo "$DEV2 does not exist."
                        exit 1
                fi

                $IP addr flush dev $DEV1
                $IP addr flush dev $DEV2
                $IP link set dev $DEV1 down
                $IP link set dev $DEV2 down
                sleep 1
                $BRCTL addbr $BR
                $BRCTL addif $BR $DEV1
                $BRCTL addif $BR $DEV2
                $IP addr add $ADDRESS brd + dev $BR
                $IP link set dev $DEV1 up
                $IP link set dev $DEV2 up
                $IP link set dev $BR up

                route add default gw $GATEWAY dev $BR
                echo "$BR is now $ADDRESS."
                ;;
        stop)
                echo -n "Stopping bridge: "
                if [ ! -d "$SYSPATH/$BR" ]; then
                        echo "$BR does not exist."
                        exit 0
                fi
                if [ ! -d "$SYSPATH/$ONSTOP" ]; then
                        echo "$ONSTOP does not exist."
                        exit 0
                fi

                $IP link set dev $DEV1 down
                $IP link set dev $DEV2 down
                $IP link set dev $BR down
                sleep 1
                $BRCTL delif $BR $DEV1
                $BRCTL delif $BR $DEV2
                $BRCTL delbr $BR
                $IP addr flush dev $ONSTOP
                $IP addr add $ADDRESS brd + dev $ONSTOP
                $IP link set dev $ONSTOP up

                echo "$ONSTOP is now $ADDRESS."
                ;;
        restart)
                $0 stop
                sleep 2
                $0 start
                if [ "$?" != "0" ]; then
                        exit 1
                fi
                /etc/init.d/dhcp3-server restart
                ;;
        *)
                echo "Usage: /etc/init.d/bridge {start|stop|restart}"
                exit 1
esac

exit 0