Squid using 2 Ethernet in Proxy System

Hi All Im using squid Proxy in centos

Squid version = squid.x86_64 7:3.1.10-20.el6_5
CentOS release 6.5 (Final)

Router IP = 192.168.1.1

My proxy System have 2 Ethernet port
eth0
eth1

Using IP address for eth0 = 192.168.1.15/24
using IP address for eth1 = 192.168.1.16/24

Default gateway for proxy system 192.168.1.1
DNS : 192.168.1.1
ADNS 8.8.8.8

I have configured transperent Squid Proxy using this below link

How to install squid proxy on centos 6

And Working, I have connected as

Internet----> Router---> Proxy System--->LAN Switch ---> User's

As mentioned in above website i have used iptables script and changed the eth0 to internet and eth1 to lan
But User's cant browseable the internet, So i have replaced eth0 for both internet and LAN if so its browseable for User's and its working, how can i fix this to work with both ethernet by getting the internet into eth0 and send the filterd data to lan using eth1, Did i need to use any other iptables rules too ? only i need to get filter some website to use by user's in my LAN, Any one guide me to get fix this issue please.

Problem Solved

I Used this Setup ----> Squid Internet Filtering Using 2 Ethernet Card's