iptables internet nat redirection (wan to lan)

Posted on 2015-01-03
Last Modified: 2015-02-02
I am trying to setup a Linux/iptables router to redirect forwarded ports from the outside/wan interface to an IP address on the inside/LAN network.  This works fine from outside of the internal network, but I also want this to happen inside the internal network.  I have read several examples and it looks like it should be working, however it is not.  I am working on redirecting port 443 currently.  In the script below the outside interface (eth0) IP is and inside interface (eth1) IP is  The internal server I want to redirect port 443 to is  This is a /24 network so the network address is  Can anyone see what I am doing wrong in the script below?

# Setting default INPUT policy to DROP
/sbin/iptables -P INPUT DROP

/sbin/iptables -A INPUT -j ACCEPT -s -d
/sbin/iptables -A INPUT -j ACCEPT -s -d
/sbin/iptables -A INPUT -j ACCEPT -s -d -i lo
/sbin/iptables -A INPUT -j ACCEPT -s -d -i eth0 -m state --state RELATED,ESTABLISHED
/sbin/iptables -A INPUT -j ACCEPT -p icmp -s -d

/sbin/iptables -A INPUT -j LOG -s -d --log-prefix ' ##INPUT DENY LOG## '

#  =====================================
#  ========== Outgoing Rules ===========
#  =====================================

# Setting default OUTPUT policy to ACCEPT
/sbin/iptables -P OUTPUT ACCEPT

/sbin/iptables -A OUTPUT -j ACCEPT -s -d
/sbin/iptables -A OUTPUT -j ACCEPT -s -d -o lo
/sbin/iptables -A OUTPUT -j ACCEPT -s -d -o tun+
/sbin/iptables -A OUTPUT -j ACCEPT -s -d -o eth0 -m state --state RELATED,ESTABLISHED
/sbin/iptables -A OUTPUT -j ACCEPT -s -d
/sbin/iptables -A OUTPUT -j ACCEPT -s -d
/sbin/iptables -A OUTPUT -j ACCEPT -p icmp -s -d
/sbin/iptables -A OUTPUT -j ACCEPT -s -d

/sbin/iptables -A OUTPUT -j LOG -s -d --log-prefix ' ##OUTPUT ACCEPT LOG## '

#  ======================================
#  ========== Forwarded Rules ===========
#  ======================================

# Setting default forward policy to DROP
/sbin/iptables -P FORWARD DROP

# Allow VPN traffic for openvpn tunnels
/sbin/iptables -A FORWARD -j ACCEPT -i tun+
/sbin/iptables -A FORWARD -j ACCEPT -o tun+

# Allow normal NAT operations
/sbin/iptables -A FORWARD -j ACCEPT -s -d -m state --state RELATED,ESTABLISHED
/sbin/iptables -A FORWARD -j ACCEPT -s -d
/sbin/iptables -A FORWARD -j ACCEPT -s -d

# Log everything else
/sbin/iptables -A FORWARD -j LOG -s -d --log-prefix ' ##FORWARD DENY LOG## '

#  ======================================
#  ========== Prerouting Rules ==========
#  ======================================

/sbin/iptables -t nat -A PREROUTING -j DNAT -p tcp -s -d --dport 443 --to

#  ======================================
#  ========= Postrouting Rules ==========
#  ======================================

# Forward all INTERNAL traffic to the correct INTERNAL IP
/sbin/iptables -t nat -A POSTROUTING -j SNAT -s -d --to-source

# Masquerade everything else
/sbin/iptables -t nat -A POSTROUTING -j SNAT -s -d -o eth0 --to-source

Open in new window

Question by:bdhtechnology
  • 4
  • 4
LVL 77

Assisted Solution

arnold earned 250 total points
ID: 40529758
To deal with outgoing traffic, you need to deal with the NAT table output, POSTrouting.

You would also use SNAT.

There is a graphical depiction to which I do not have a link at hand, it depicts the iptable stracture
Look for linux as a router,
Input forward PREROUTING output dealswith external to internal traffic,
You need to work on the other table and reversing the path.
LVL 77

Expert Comment

ID: 40529766
Look at which may help you withthe control of the outgoing traffic.

--to-address ....

Your IPtables rules seem wrong using NAT IPs.

You should use interface designations to make sure which you are dealing with.

Author Comment

ID: 40530152
That looks like an interesting tool, though I would have to learn a new tool to figure this one out :)

I feel like it is pretty close, when I examine the logs I see each of the rules has an equal number of packets, so they are being run, but I believe something is just a bit off.

Here are the 2 rules I am working with specifically.  I will try to find the page with the example I am working off of

iptables -t nat -A PREROUTING -j DNAT -p tcp -s -d --dport 443 --to
iptables -t nat -A POSTROUTING -j SNAT -s -d --to-source
LVL 77

Expert Comment

ID: 40530180
Th ile needs to be in input and forward.

Is your setup is such that your linu box is functioning as a router.

Often I oukd suggest you relate IP chains
On using the wan interface -i interface as the limiter
I.e. This way you can add a rule to the chain and it will result in the addition of the same rule to the two appropriate input PREROUTING, forward on one side incoming rules
Nd no thr using outgoing rules fom the LAN interface.

Your second one, you oukd not use SNAT to alter the source IP as 1.254 but rather alter the source to reflect the WAN IP you want the packet to appear as originating.
This deals ith you having multiple public IPs
SNAT would reflect the when the internal source is

Or m I not understanding hat you want your main wan IP is
Internet access to1.2.3.5:443 you want to end up on server
You then want the response to appear as originating from to match
VMware Disaster Recovery and Data Protection

In this expert guide, you’ll learn about the components of a Modern Data Center. You will use cases for the value-added capabilities of Veeam®, including combining backup and replication for VMware disaster recovery and using replication for data center migration.


Author Comment

ID: 40530873
Yes the Linux box is functioning as a router.  

Basically all I want is packets sent to the main WAN IP of on port 443 to be redirected to on port 443.  It doesn't matter to me if the response appears as originating from the WAN IP or the local IP address of the device, as long as they can access it.
LVL 77

Expert Comment

ID: 40530895
iptables -t nat -I PREROUTING 4 --dport 443 -t tcp -m tcp --to -j DNAT
iptables  -I FORWARD 1 -m tcp -p tcp --dport 443 --to -j ACCEPT

-I tells it  to insert the instruction, number 4 tells it to on line 4.

see if that solves your issue.

There are many linus as router/prot forward examples, is one.

Using IP chains, is often better as you can your own created IPCHAIN
with interface restriction and the type.

Then when you add a rule to the chain, it will be reflected in both PREROUTING and FORWARDING on the incoming side
LVL 34

Assisted Solution

by:Duncan Roe
Duncan Roe earned 250 total points
ID: 40532228
I think you want to leave the source address of internally generated --dport 443 packets alone. The replies will go to the right systems, bypassing the router.

Accepted Solution

bdhtechnology earned 0 total points
ID: 40575971
This is apparently working, except from  the server itself.

Author Closing Comment

ID: 40583578
started working

Featured Post

Efficient way to get backups off site to Azure

This user guide provides instructions on how to deploy and configure both a StoneFly Scale Out NAS Enterprise Cloud Drive virtual machine and Veeam Cloud Connect in the Microsoft Azure Cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have seen several blogs and forum entries elsewhere state that because NTFS volumes do not support linux ownership or permissions, they cannot be used for anonymous ftp upload through the vsftpd program.   IT can be done and here's how to get i…
Little introduction about CP: CP is a command on linux that use to copy files and folder from one location to another location. Example usage of CP as follow: cp /myfoder /pathto/destination/folder/ cp abc.tar.gz /pathto/destination/folder/ab…
Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…
Connecting to an Amazon Linux EC2 Instance from Windows Using PuTTY.

932 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

8 Experts available now in Live!

Get 1:1 Help Now