I have the following in /etc/rc.local on my router (ip 192.168.10.2) to transparent proxy to squid proxy with dansguardian ip 192.168.10.16. All works perfectly but I am having trouble adding a machine that I do not want to transparent proxy. If my proxy goes down I want to be able to access the internet to try to figure out the problem. I also do not want to proxy a specific server. Thank you kindly for any help and advice. The proxy has dansguardian on port 8080 and squid on 3128.

#!/bin/sh
#NOTE:
#eth0 is the green or internal nic
#eth1 is the red or external nic
#redirect to dansguardian so that there is a tranparent proxy.
iptables -t nat -A PREROUTING -i eth0 -s ! 192.168.10.16 -p tcp --dport 80 -j DNAT --to 192.168.10.16:8080
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.10.0/24 -d 192.168.10.16 -j SNAT --to 192.168.10.2
iptables -A FORWARD -s 192.168.10.0/24 -d 192.168.10.16 -i eth1 -o eth0 -p tcp --dport 3128 -j ACCEPT