In computer networking, network address translation (NAT) is the process of modifying network address information in datagram (IP) packet headers while in transit across a traffic routing device for the purpose of remapping one IP address space into another.

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Routing application traffic through specific interface

First question here, so please go easy: I have a debian linux 5.0 server with two public interfaces. I would like to route outbound traffic from one instance of an application via one interface and ...
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Marking packets with iptables with a NAT

I have to write bash scripts for a router to control bandwidth limitation for a given user on a given domain name. For this, I'm using iptables to mark the packets incoming from a restricted domain ...
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Linux Routing with two NICs (LAN vs Internet) with NAT and bridging for VMs

My Setup: There is only one physical machine in this setup, a Host System for Virtual Machines (VMs) with two network adapters. One NIC (eth0) is connected to an internal network (LAN subnet, e.g. ...
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Is it possible to configure a reverse VPN tunnel?

Basically, my goal is to have a 100% portable and independent server. I'm building it using a Raspberry Pi powered by solar panels and batteries, and it is to be connected to the internet using a 4g ...
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What is the correct iptables rule when NATing multiple private subnets?

I have a Centos minimal 6.5 acting as a router. eth0 is connected to a Cisco switch trunk port, allowing VLANs 200-213. I have several VLAN interfaces just as this link suggests: https://access....
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How to Configure Source NAT (Private IP => Public IP Outbound)

I'm running VMWare ESXi Free and have Zentyal SBS 3.2 running as a Gateway. I have 5 Public IPS (CIDR/29, let's call them 69.1.1.1 - 69.1.1.5) and currently Zentyal is bound to 69.1.1.1 as the ...
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How are connections differentiated from behind NAT routers?

Background: I have a very simple server program written in PHP. It's mostly working, but only as long as there is not more than one client per site. Questions: How does a NAT Router (typical SOHO ...
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NAT: If two hosts initiate a connection to the same IP:PORT, with the same source PORT, how does the router handle it?

I was just thinking and that idea came to my mind. Let say I have hosts A and B inside my local area network. I have a Router, and a host C in the internet. I know that when initiating the connection,...
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How to redirect ports for on a virtual interface?

There are two IPs associated with one physical network interface eth0 and eth0:0. The following works fine for the first interface: iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -j ...
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iptables asynchronous NAT. packets drop after prerouting table

I have a Centos server acting as a NAT in my network. This server has one external (later ext1) interface and three internal (later int1, int2 and int3). Egress traffic comes from users via int1 and ...
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How Do I Block an IP Address on ubuntu?

I have configured Ubuntu machine as router. Steps of NAT configuration are given below: #iptables -F #iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE #iptables-save >...
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many different TCP timestamps through NAT device cause server to drop packets (PAWS)

Various workstations behind the client side Network Address Translation (NAT) firewall are sending timestamp information on the TCP packet to our server. The packets from many workstations arrive ...
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Routing requests from external hostnames to internal IP addresses in Ubuntu

I want to host several websites using the same IP address. My ISP gives me one static IP address, however I have three different webservers (all running different sites) hooked up behind a cheap ...
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1answer
640 views

IP NAT pool range

When is it necessary to setup a pool of more than one address? So if I have this ip pool range: ip nat pool demo 72.32.11.65 72.32.11.66 netmask 255.255.255.252 What's the difference if I just have ...
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How do I setup Windows Server 2008 as NAT with one NIC?

How would I setup Windows Server 2008 as NAT router with only one nic? I only have access to a server with one nic and I can't add a nic to the server.
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AWS public subnet autoscaling group with outbound NAT

I have seen this question : Static IP address for outgoing traffic from AWS autoscaling group but it doesnt seem to fit exactly what im trying to do. Here's the scenario: I have a autoscaling ...
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3answers
249 views

Cisco ASA NAT - internal host see its public ip

I have a server hosted by a provider which uses Cisco ASA to do nat. The problem I have is that the internal server that is nat-ed with a public ip will see its public ip as source ip. This basically ...
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NAT a single IP using 2nd WAN Internet

I have a mikrotik RB750 (6.22) acting as a gateway for my LAN. Here is the basic configuration: Ether1-WAN1 (1.1.1.10/24) IPs are hidden for privacy Ether2-WAN2 (2.2.2.20/24) Ether5-LAN (192.168.1.1/...
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How can I know if NAT instance is becoming a bottleneck

I'm running my own NAT instance inside of an AWS VPC. I want to make sure that the NAT instance will not be a bottleneck and to that end would like to set my own expectation for when to scale to a ...
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3answers
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iptables: combine SNAT with network remapping for OpenVPN

[Apologies for the long prelude; question halfway down.] I have a working OpenVPN setup whereby a VPN server pushes a route back to one client (hereafter called the “router”) which can then expose ...
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Sharing an internet connection from a virtual Windows 2012 AD Server

I have a virtual HyperV network used by a number of virtual development and testing servers and an all-in-one Domain, DNS, DHCP server; I want to keep the many virtual servers separated from our main ...
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Cisco Network Object NAT to get Internet?

So I've inherited a Cisco ASA 5505, and I have no experience whatsoever with the things! There are two Network Interfaces both WAN facing, and the LAN interface of course. Now in NAT rules, there are ...
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Configure VirtualBox webserver to see visitors IP address

I finally managed to move my server to VirtualBox virtual machine. VM is running in NAT mode. I have forwarded necessary ports, including the port 80 which I first fowarded with iptables to port 8888,...
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How can I NAT traffic for one VPN to come from a different IP on Cisco ASA?

I have a Cisco ASA firewall between our private network (10.1.0.0/16) and the outside world, and multiple VPNS going to client sites. Existing: [10.1.0.2...] = source client | [10.1.0.1 ASA &...
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tcpdump not picking up traffic redirected by iptables

The following iptables rule is used to redirect all internet traffic coming in from eth1 to port 3000 at localhost (interface lo with ip 127.0.0.1): iptables -t nat -A PREROUTING -i eth1 -p tcp --...
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1answer
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Building a router / NAT and need to compare performance of FreeBSD 8 v RHEL 6 [closed]

I am going to be setting up a router and NAT device but I am unable to choose between pfSense 2.x (FreeBSD 8) and RHEL 6. The device will need to forward a medium (2k hosts) sized network where ...
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2answers
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iptables: How to forward packets with destination port 80 from eth0 to eth1?

I've http and https traffic coming from several machines to my eth0 on my Linux machine, but I want to forward these traffic to eth1 which has the access to the internet. And do the complimentary ...
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Does hole punching require a UDP rendezvous server Or could it be a TCP one?

I'm trying to get my head wrap around this issue... I would like to connect two users... Those users are already connected to a TCP server, which is aware of both public ip and connection TCP port. ...
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1answer
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ASA Static NAT Understanding

I have an ASA configured as follows; Inside: 192.168.0.254/24 Outside: 10.0.0.1/29 (This is routed to the ASA) global (outside) 1 interface global (outside) 2 10.0.0.2 nat (inside) 1 0.0.0.0 0.0.0.0 ...
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Cisco ASA Nat 8.4

I'm trying to get port forwarding on my ASA working. I'm using: object network server1 nat (inside,outside) static interface service tcp 25 25 and an access list, and it works fine, however, I ...
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iptables masquerading and rejecting outside-to-inside

I found masquerading made simple howto very useful and everything works just fine. But I'm not sure about the last line: iptables -F iptables -t nat -F iptables -t mangle -F iptables -t nat -A ...
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Making Ubuntu a minimal NAT?

I need to make a quick-and-dirty NAT out of a Ubuntu 10.10 box. Just "this side is NATted with DHCP handing out 192.168.x.0/24" and "this side gateways to the Internet", and nothing else interesting. ...
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1answer
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How to access Apache virtual-host in VMware guest through NAT?

As a webdeveloper I have an Apache server running on my local machine which I use for developing. The server is listening on every IP address on port 80 as per default. However I've used the httpd....
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How can I copy from a server on the internet to a server behind a router doing NAT?

I have both a VPS and a server behind a NAT firewall. I want to use the server behind a NAT firewall as a backup for the VPS. The VPS needs to be able to initiate the backup process and send the ...
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Best way to monitor network traffic through a linux gateway

I have a linux box set up running as a router using iptables. My question is: What is the best way to monitor the traffic passing through it, on a per-IP basis? I've tried using Ntop, but it just ...
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Tunneling XBox network traffic [closed]

My internet access from home is only via a web proxy and a tcp-only socks 5 server. (Long story don't ask). I recently got an xbox and would like to access xbox-live. but I need to route the ip ...
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How can I connect remotely to our network from behind a double NAT?

Having successfully set up my home office network for remote access via OpenVPN, I would now like to do the same thing at work, however I am double natted. There is a central router maintained by ...
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1answer
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How to make connections answer from the same gateway they entered in RouterOS?

I have a MikroTik RouterOS 6.23 device, and my network is as follows: Router | |-- bridge1_LAN (wlan1 + ether1) (192.168.0.210) -- LAN (192.168.0.0/24) | Here is where computers are. Those ...
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2answers
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OpenWRT Barrier Breaker - Router does not route

I've upgraded my TP-Link 1043 router to OpenWrt 14.07. Everything is perfect, Wifi and LAN are bridged, LAN machines can access each other by name, I can SSH into the router, and the router can access ...
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2answers
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Iptables does not seem to be applying SNAT to packets sent on a raw socket

I'm sending packets from a user space program to my wireless interface wlan0. I've set up a SNAT rule with iptables as follows iptables -t nat -A POSTROUTING -o wlan0 -j SNAT --to 192.168.1.3 And ...
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1answer
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strongSwan setup where both sides are behind NAT

I'm trying to setup a strongSwan server in my home and connect to it from another network. Let's say sun is the VPN server and venus is the client. Both sun and venus are behind NAT networks. sun is ...
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2answers
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libvirt and network filtering with nat - iptables overrides

At first, I want to say: I know, it was done initially wrong and I want to avoid doing everything again from the scratch because of general downtime. I am running libvirt/KVM on RHEL. I've got VM ...
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Setting up NAT for multiple isolated networks with iptables

I have a gateway machine connected to multiple internal networks that I would like to set up NAT on. The catch, though, is that these networks need to be isolated from each other, which I haven't been ...
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1answer
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Can't connect to instance via floating IPs, not natting/forwarding properly

I'm having trouble getting floating IPs to work properly on my OpenStack setup. It looks like the controller node (running nova-network) isn't forwarding the traffic to the instances. I've got a ...
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3answers
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Is it possible to capture packets of a Router?

I am facing an issue that some packets sent out to internet from inside network were missing. The pattern we are using is like: Client A ←→ Switch A ← Router A:NAT ← .. Network .. → Router B:...
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Netgear VPN LAN2LAN address translation

Here's my question: I have set up a VPN IPsec LAN2LAN (or site2site) with the following parameters: local subnet: 10.178.51.64/27 remote subnet : 10.174.0.0/16 The vpn tunnel comes up correctly ...
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IPtables SNAT eats packets

I am trying to translate outgoing UDP packets with a source port of X to a source port of Y. I have done this using the following iptables rule: iptables -t nat -A POSTROUTING -s 10.0.0.1 -p udp --...
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2answers
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Iptables: Forwarding packets doesn't work

I have 3 Linux Systems A, B and C. A is a TCP Client and sends a message to TCP Server on C. A can see only the external IP of B which is at wlan0 interface, 192.168.0.3 ------------------ ...
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NAT setup for an SIP Registrar/Proxy

I am currently trying to get the following scenario to work. Warning: I am a software engineer--not a network admin. I have various SIP endpoints (sip based video servers) on a LAN. On a Windows ...
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1answer
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Trouble with NATing

I'm a networking noob, so sorry for the very generic title. I have the network setup in the following way: A few details about the network: eth0 on all the devices have an in IP in 10.10.10.0 ...