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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IPSec Tunnel to Amazon EC2 - Netkey, NAT, and routing issue

I'm working on getting an IPSec VPN working between Amazon EC2 and my on-premise. The goal is to be able to safely administer stuff, up/download data, etc. over that tunnel. I have gotten the tunnel ...
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VirtualBox - Static Guest, accessible from host

I'm using VirtualBox trying to set up Windows as my dev environment, but an Ubuntu VM as my "virtual server". So, Windows 7 is my host OS on my laptop. My guest OS is Ubuntu, which will run my LAMP ...
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ASA 5505: How do I access the DMZ web server from the inside using the public IP?

We are using a 5505 ASA Sec+ (8.2). There are three interfaces: inside (172.17.0.0/24), dmz (172.16.0.0/24) and outside (1.2.3.4 for the example). There are static NAT rules set up translating ...
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74 views

Reaching out DHCP relayed hosts

I have one primary server (DHCP) and one secondary (DHCP-RELAY). Majority of hosts are served from primary (wirelessly), however there are a few (wired ones) which get their IPs from secondary. ...
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482 views

Openstack seems to not map internal IPs to local network properly

I have a very confusing issue which I can't seem to resolve. I followed a guide by Loic Dachary on installing Openstack Folsom on Wheezy, and deployed it on two hosts: a cluster node, and my ...
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349 views

NAT box load-balancing with iptables and 4 DHCP uplinks

I am trying to configure a router which provides Internet to a couple hundred users. This router has 4 basic cable uplinks at its disposition, which all use DHCP and have a capacity of around 10/1 ...
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506 views

Oracle Solaris 11, ipnat - rdr not working with remote destinations

I'm trying to reverse proxy traffic coming in on port 8100 at one machine to another. The receiving host is an oracle exclusive zone as is the destination machine. On the incoming zone I have ...
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2answers
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sonicwall vpn and NAT

I have a site-to-site VPN set up with a vendor. Let's say the tunnel endpoints are 192.1.1.101 on my side and 192.1.2.0/24 on the vendor's side (which get's NATted to their LAN of 10.x.x.x). This is ...
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Open ports broken from internal network [duplicate]

Quick summary: Forwarded port works from the outside world, but from the internal network using the external IP the connection is refused. This is a simplified situation to make the explanation ...
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4answers
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Is there still any legitimate reason (in 2011) to use proxy servers instead of NAT for sharing an internet connection?

Proxies were around before NAT, and so early on in the internet, they were popular ways to get an entire network online with only a single public IP. NAT initially required complex software and/or ...
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3answers
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Iptables massive 1:1 NAT

I have to connect two LANs: LAN1: 10.10.0.0/16 and LAN2: 192.168.0.0/16. I can't do simple routing, because 192.168.0.0/16 net is prohibited in LAN1, so I am thinking of using Full cone nat (1:1) to ...
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Windows Computers Joined to a Domain Behind NAT

If I have some Windows XP machines that are behind NAT, will all services still work as normal such as file sharing, printing, etc. The setup would be something like 192.168.20.0/24 NAT`ed to ...
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2answers
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Server becomes unreachable and comes back up on its own (most likely a network issue)

I'm having a strange problem with a server I have sitting at my workplace (it's behind a NAT, if that's important). The issue is that at some times, it becomes unreachable and then comes back up ...
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2answers
3k views

Domain Controllers over a NAT

My organization is in the process of setting up a new network at a hosting provider for a very large application project. Since the whole system uses Active Directory we are planning on using a pair ...
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2answers
939 views

Iptables string

I have an iptables rule like this: iptables -t nat -I PREROUTING -p tcp --dport 80 -s 192.168.1.2 -j DNAT --to-destination 192.168.1.1:80 it works perfectly.. but I want to redirect only for one ...
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1answer
104 views

How can I Nat certain boxes in my datacenter so that they are coming from a single IP

I want to NAT a certain group of servers in my datacenter so that they all access clients from a single IP. This will make it much easier for documentation that we provide clients. However there ...
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1answer
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How do I configure port forwarding on a Watchguard XTM 2?

I have one external static IP that is nat'ed by the XTM to a local network, I would to be able to configure port forwarding on it (say external:80 -> 10.0.1.43:80 and external:2340 -> 10.0.1.48:2340). ...
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2answers
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PPTP/GRE Multi-forwarding NAT IPTables Example

Google is showing me some returns on PPTP/GRE NAT through iptables/netfilter that will allow multiple connections. However, I am not finding an example of using this pptp helper module that allows ...
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3answers
842 views

Can I have web server on a home network with 1 public IP address? [closed]

I've got a fairly standard home network with a modem from my ISP, which is connected to a router which then provides NAT to about 3 PCs and laptops. There's a possibility to obtain one public IP from ...
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4answers
755 views

Is NAT completely transparent to a host?

Can we find a sequence of packets that a host can transmit to determine whether it is located behind a NAT box? I mean, without any special server support like STUN.
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3answers
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How to implement Nat loopback/reflection?

I'm trying to access a server on my LAN via its public IP address. External clients can connect just fine, but I'm unable to do so from within the LAN. There is a separate rule in the NAT settings of ...
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1answer
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Cisco ASA 8.4 port forwarding

I am having trouble port-forwarding on an Cisco ASA from a host on the internet to a host on the internal network. The outside interface of the ASA is assigned via DHCP. Is there something else that ...
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2answers
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UDP and NATs - is the timeout bidirectional?

Is the timeout for an UDP connection through a NAT reset every time a packet is sent OR received by the client, or are there any (common) implementations that require the client to actively send ...
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3answers
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VPN software similar to Hamachi, Remobo or GBridge?

I am looking for a VPN software that will run on Windows (Mac/Linux would be a bonus), that are similar to other packages such as Hamachi that will automatically work behind a NAT or Firewall. ...
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4answers
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Networks, subnets, routing and NAT

What I'm going to ask may be trivial but I really need to understand cause my teacher is confusing me! That's the problem. I got 2 private networks The first is a class C network and the address is ...
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2answers
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Make CentOS 7.x a port forwarding NAT device

I would like to make CentOS a port forwarding NAT machine using iptables. This is the first time I've tried this and I think i might need a little help. This is the configuration i'm trying to ...
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2answers
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IPtables NAT puzzler: Why is traffic from the firewall host being NATed even though it's not coming from one of the prescribed source addresses?

I run a small network where a linux web/mail server also provides NAT for a collection of windows boxes. One of these windows machines is apparently misbehaving (ZeroAccess botnet even though I can't ...
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2answers
298 views

Networking several devices with the same IP

I have a bunch of embedded devices that I need to flash with a custom OS. On each device, the boot-loader (U-Boot) has a fixed IP of 192.168.100.2 and on boot it looks for a TFTP server at ...
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2answers
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How can I setup a Firewall without NAT?

We have 16 IP addresses from our ISP, and are setting up a SonicWall Firewall. I'd like to have the SonicWall do NAT for the LAN, but act as a firewall only (no NAT) for the servers which are using ...
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3answers
594 views

Port Forwarding

Assuming port forwarding is done on router, can the router forward if the data is coming from local machine, rather than remote. For example: Sender targets ip like:88.251.xxx.xxx, port 8999. ...
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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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1answer
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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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2answers
658 views

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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3answers
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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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1answer
331 views

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: ...
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1answer
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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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555 views

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 ...
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1answer
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OS X 10.8: redirecting locally initiated ssh connections to localhost:22

I need to hack the OS X pf to redirect all ssh connections from an user to this machine. I want, when doing $ ssh google.com to get the same results as with $ ssh localhost ie a connection to ...
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2answers
755 views

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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1answer
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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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3answers
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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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1answer
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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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1answer
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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
630 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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1answer
837 views

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
220 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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2answers
908 views

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 ...
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1answer
948 views

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 ...