Port forwarding from port 80 to port 8090 (assuming this traffic_router server is running at port 8090).  

Website referred: https://kerneltalks.com/networking/how-to-forward-port-using-iptables-in-linux/


STEP 1: ENABLE PORT FORWARDING IN LINUX

NOTE: Network interface is taken as ens3. It may differ; identify exact value using command such as $ ifconfig.

Check port forwarding status in two different approaches:

Approach a: 
$ sudo sysctl -a | grep -i ens3.forwarding
net.ipv4.conf.ens3.forwarding = 0
net.ipv6.conf.ens3.forwarding = 0

0 indicates port forwarding is NOT ENABLED

Approach b:
$ sudo cat /proc/sys/net/ipv4/conf/ens3/forwarding
0

To enable:
$ sudo sysctl net.ipv4.conf.ens3.forwarding=1



STEP 2: FORWARD PORT IN LINUX

Step 2a:
$ sudo iptables -A PREROUTING -t nat -i ens3 -p tcp --dport 80 -j REDIRECT --to-ports 8090
OR
$ sudo iptables -A PREROUTING -t nat -i ens3 -p tcp --dport 80 -j DNAT --to 165.22.215.207:8090

$ sudo iptables -A PREROUTING -t nat -i ens3 -p tcp --dport 443 -j REDIRECT --to-ports 8091
OR
$ sudo iptables -A PREROUTING -t nat -i ens3 -p tcp --dport 443 -j DNAT --to 165.22.215.207:8091

Step 2b:
$ sudo iptables -A FORWARD -p tcp -d 165.22.215.207 --dport 8090 -j ACCEPT
$ sudo iptables -A FORWARD -p tcp -d 165.22.215.207 --dport 8091 -j ACCEPT

Step 2c:
Check the update of PREROUTING rows in NAT (Network Address Translation) table with the following command
$ sudo iptables -L PREROUTING -n -v -t nat --line-numbers     

Check the updates of FORWARD rows in filter table 
$ sudo iptables -L FORWARD -n -v -t filter --line-numbers     

To Delete a PREROUTING row in nat table, say line number 2
$ sudo iptables -t nat -D PREROUTING 2 



STEP 3: ENSURE ENTERIES AT /etc/hosts:
127.0.0.1   localhost
127.0.0.1   www.eastgate.test
127.0.0.1   nav.eastgate.test
127.0.0.1   login_app.eastgate.test  
127.0.0.1   todo_app.eastgate.test  
127.0.0.1   todo_web.eastgate.test  
127.0.0.1   comment_app_demo.eastgate.test