To bridge the interfaces on a Synology NAS:

SSH in to the NAS, switch to root, and put this in a file named /root/

insmod /lib/modules/stp.ko
insmod /lib/modules/bridge.ko
brctl addbr br0
brctl stp br0 off
brctl addif br0 eth0
brctl addif br0 eth1
brctl show
ifconfig eth0 promisc up
ifconfig eth1 promisc up
ifconfig br0 netmask up
route add default gw dev br0
echo "1" > /proc/sys/net/ipv4/ip_forward
cp /root/ /usr/syno/etc.defaults/rc.d/
chmod 755 /usr/syno/etc.defaults/rc.d/

Replace the IP above with the static IP for the NAS.

Then run:

# chmod 755
# ./
# cp /usr/syno/etc.defaults/rc.d/</pre>