diff --git a/build/sims/tap.sh b/build/sims/tap.sh
new file mode 100755
index 00000000..4272cd5b
--- /dev/null
+++ b/build/sims/tap.sh
@@ -0,0 +1,63 @@
+#!/bin/sh
+
+ETH="$2"
+HOSTIP="$3"
+TAP=tap0
+BRIDGE=br0
+USER=${SUDO_USER:-`whoami`}
+
+usage() {
+    echo "Usage: $0 start|stop interface [address]"
+    exit 1
+}
+
+start() {
+    test -z "$HOSTIP" && usage
+
+    echo "WARNING!  This script may mess up your network configuration."
+    echo "The current configuration will be logged to config.log."
+    echo "Type Enter to continue."
+    read foo
+
+    brctl show > config.log
+    ifconfig -a >> config.log
+    route -n > config.log
+
+    #
+    tunctl -t $TAP -u $USER
+    ifconfig $TAP 0.0.0.0 down
+    ifconfig $ETH 0.0.0.0 down
+    brctl addbr $BRIDGE
+    brctl setfd $BRIDGE 0
+    brctl addif $BRIDGE $ETH $TAP
+    ifconfig $BRIDGE up
+    ifconfig $TAP up
+    ifconfig $ETH up
+
+    dhclient -v $BRIDGE
+
+    route add -host $HOSTIP dev br0
+
+    ifconfig $TAP | head -2
+    ifconfig $ETH | head -2
+    ifconfig $BRIDGE | head -2
+    route -n
+}
+
+stop()
+{
+    ifconfig $BRIDGE 0.0.0.0 down
+    ifconfig $TAP 0.0.0.0 down
+    ifconfig $ETH 0.0.0.0 down
+    brctl delif $BRIDGE $ETH $TAP
+    brctl delbr $BRIDGE
+    tunctl -d tap0
+    ifconfig $ETH up
+    dhclient $ETH
+}
+
+test -z "$1" && usage
+test -z "$2" && usage
+
+set -e
+"$1"