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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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
746 views

Public IP behind NAT firewall

I have a Linux NAT Firewall serving a virtual machine infrastructure. Right now all the VMs use NAT, but I'd like to have some of them to use a public IP that is not NATed. I have a range of IPs: ...
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4answers
663 views

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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3answers
3k views

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
2k views

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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1answer
147 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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2answers
385 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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2answers
584 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
860 views

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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1answer
1k views

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 ...
2
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1answer
600 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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3answers
538 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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1answer
3k views

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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1answer
472 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 ...
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4answers
1k views

Linux - two subnets, one interface, one gateway - NAT the additional subnet

We currently have a few servers that all use the same LAN: Host1: eth0 10.0.0.1/24 Host2: eth0 10.0.0.2/24 Host3: eth0 10.0.0.3/24 Gateway: 10.0.0.254 We want to run some VMs (VirtualBox) on these ...
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3answers
2k views

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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1answer
776 views

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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2answers
85 views

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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1answer
500 views

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 ...
2
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1answer
2k views

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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2answers
4k views

Basic iptables NAT port forwarding

I have three machines: A local PC (public IP 1.2.3.4), an Ubuntu 10 Server box in a datacentre (eth0 on 5.6.7.8 public IP), and a third-party server hosting a website outside of my network (let's say ...
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1answer
2k views

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
1k views

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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1answer
168 views

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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2answers
669 views

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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4answers
161 views

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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2answers
2k views

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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3answers
3k views

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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3answers
52 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
810 views

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
323 views

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
649 views

Ping responses to floating IPs do not reach the router (iptables/nat)

I'm running OpenStack, and I'm having trouble accessing my instances from floating IPs, from anywhere except the network controller node. I've got a Folsom deployment with FlatDHCP, not running ...
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1answer
480 views

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
1k views

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 ...
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3answers
688 views

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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2answers
1k views

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
6k views

iptables: How to combine DNAT and SNAT to use a secondary IP address?

There are lots of questions on here about iptables DNAT/SNAT setups but I haven't found one that solves my current problem. I have services bound to the IP address of eth0 (e.g. 192.168.0.20) and I ...
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2answers
10k views

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 ...
2
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1answer
2k views

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
3k views

Understanding ipsec with NAT and dynamic IP's

I'm using OpenSWAN to set up a net-to-net VPN tunnel. I have succeeded in configuring a test scenario as follows: About test and test2: they are Ubuntu 12.04 virtual machines created using ...
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1answer
2k views

iperf-like bidirectional bandwidth measurement through NAT

I am using iperf to measure my uplink speed between my home PC behind NAT and a fully accessible root server. It does so using a TCP connection. For whatever reason it seems that iperf can only ...
2
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1answer
81 views

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 ...
2
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1answer
550 views

IPTables Internal Load Balancing

I'm trying to setup a load balancing within the same LAN using IPTables (if possible). My idea is to emulate our main load balancer, but within a virtual environment, all the servers are virtual ...
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1answer
518 views

Static routes for making hosts on different network accessible

I have a ubuntu router machine with following network settings: br0 192.168.1.15 netmask 255.255.255.0 br0:1 192.168.2.209 netmask 255.255.255.248 I have a pc attached to the br0:1 network with ...
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3answers
301 views

How can Facebook's session get mixed up because of NAT and/or Proxy

Have received some reports from a customer (a very large company) they reported issues from clients who are using Facebook. These clients claim that once in a while when they log in to Facebook they ...
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5answers
379 views

problem with NAT in a multiple uplink scenario

I'm trying to configure a linux pc-router that must deal with routing and using NAT to provide connectivity to an internal network (it's also the DHCP server and firewall). In the external side the ...
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1answer
2k views

How to forward host ports of < 1024 to a VirtualBox NAT-connected machine?

The manual says: "Forwarding host ports < 1024 impossible: On Unix-based hosts (e.g. Linux, Solaris, Mac OS X) it is not possible to bind to ports below 1024 from applications that are not run by ...
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1answer
940 views

asterisk/freeswitch in nat/no-nat setup

my current setup - i use bunch of sip hard-phones around few offices. all devices have two sip accounts configured - one on internal sip proxy [for calls between the branches], another - at 3rd party ...
2
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2answers
3k views

How do you implement NAT-T passthrough on a Juniper SRX series Firewall?

We have 3 juniper SRX-100 firewalls, they are configured like so: FW1 -> FW2 -> INTERNET -> FW3 We would like to create an IPSEC tunnel between FW3 and FW1 passing through FW2 preferably using ...
2
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2answers
326 views

Potential double NAT problems in an OS X office

We have a Comcast SMC Business Gateway router/modem combo in our office, and it doesn't provide much in the way of diagnostic tools or QoS routing. I want to plug another router with Tomato installed ...