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.

learn more… | top users | synonyms

32
votes
5answers
2k views

Will everyone having Globally Accessible IP's in IPv6 be kind of a security nightmare? [duplicate]

Possible Duplicate: Switch to IPv6 and get rid of NAT? Are you kidding? I'm thinking about the way that in IPv4 most of the time you have a single point to configure a firewall on, mainly ...
28
votes
7answers
11k views

How many computers can have the same public IP?

I've got a list of hundreds of page requests from the same IP and I need to know if these could be requests by different computers.
20
votes
10answers
18k views

Windows Server 2008: specifying the default IP address when NIC has multiple addresses

I have a Windows Server which has ~10 IP addresses statically bound. The problem is I don't know how to specify the default IP address. Sometimes when I assign a new address to the NIC, the default ...
17
votes
7answers
2k views

Why don't more organizations use inside-to-inside NAT or similar solutions to allow NAT hairpins?

Inside-to-inside NAT aka NAT loopback solves hairpin NAT issues when accessing a web server on the external interface of an ASA or similar device from computers on the internal interface. This ...
13
votes
7answers
6k views

Why is it a bad idea to use multiple NAT layers or is it?

The computer network of an organization has a NAT with 192.168/16 IP address range. There is a department with a server that has an IP address 192.168.x.y and this server handles hosts of this ...
12
votes
1answer
21k views

What is the difference between a Source NAT, Destination NAT and Masquerading?

What is the difference between a Source NAT, Destination NAT and Masquerading? For example, I thought IP Masqurading was what they used to call it in Linux? But what confuses me is that in our Astaro ...
12
votes
3answers
30k views

VMWare networking mode (NAT or Bridged)?

I am running Windows 7 within a virtual Machine from my Mac. I use Windows 7 for Visual Studio primarily and also to host a dev install of IIS. There are two things I need and I am not sure what ...
9
votes
3answers
3k views

Exposing multiple servers behind NAT using a single public IP address

This is a Canonical Question about NAT and DNS I'm currently trying to set up a network with a DMZ containing a web server and an e-mail server separated from the Internet by a network address ...
9
votes
3answers
12k views

Forwarding ports to guests in libvirt / KVM

How can I forward ports on a server running libvirt/KVM to specified ports on VM's, when using NAT? For example, the host has a public IP of 1.2.3.4. I want to forward port 80 to 10.0.0.1 and port 22 ...
9
votes
7answers
3k views

Loopback to forwarded Public IP address from local network - Hairpin NAT

This is a Canonical Question about Hairpin NAT (Loopback NAT). The generic form of this question is: We have a network with clients, a server, and a NAT Router. There is port forwarding on the ...
8
votes
2answers
4k views

How to configure a static wildcard subdomain with dnsmasq

I have a network behind a NAT with a few machines. The machines are: router - NAT, dnsmasq, forwarding - directly connected to the inet server - which runs ssh, www and some other stuff clients - ...
8
votes
1answer
3k views

iptables: Port forwarding with masquerading is not working

I'm having some issues with my port forwards. NAT seems to work ok and one out of the port forwards seem to work (udp port 7887 to machine 192.168.1.100). But not the others. I doubt that it matters, ...
7
votes
3answers
6k views

How to configure a custom NAT for use in Amazon VPC

I have an Ubuntu box I wish to use as NAT instance (among other things). I would prefer to avoid using the NAT AMIs provided by Amazon, and instead configuring NAT myself. Currently, my host has a ...
7
votes
2answers
703 views

IPv6 without nat but what about an isp change?

I haven't worked with IPv6 outside of 4to6 tunneling on my home pc with stuff like GoGoNet. I've read about how it works in a general way. No NAT required (or suggested) and each client uses a public ...
7
votes
2answers
198 views

FreeBSD's ng_nat stopping pass the packets periodically

I have FreeBSD router: #uname 9.1-STABLE FreeBSD 9.1-STABLE #0: Fri Jan 18 16:20:47 YEKT 2013 It's a powerful computer with a lot of memory #top -S last pid: 45076; load averages: 1.54, 1.46, ...
6
votes
9answers
2k views

How common is NAT within companies (one public ip address)?

How common is for companies to let many users share only one public ip address? I hope the answer is "not very common" since I'm developing software that depends on the ip number being pretty much ...
6
votes
1answer
262 views

How do I configure NAT rules when using ASA IP-SLA when leveraging post-ASA-8.3 NAT syntax?

We are currently running ASA9 at a location with redundant ip connectivity. We'd love to configure ip sla so that internet access survives a single carrier outage. I'm aware of the ip sla commands, ...
6
votes
9answers
2k views

Need prosumer router/firewall/vpn/vlan/nat advice [closed]

Looking for a recommendation on a device (or devices I guess) to do router/firewall/vpn/vlan/nat functons for my home network. Right now, I'm doing this with an IPCop box, but I'd prefer a little ...
6
votes
2answers
2k views

DMZ subnet: to NAT or not to NAT?

I'm looking at setting up a DMZ behind a Cisco ASA that will contain a large number of HTTP front-end load balancers and SSL offload services - over 100 IPs, concentrated on a smaller number of hosts. ...
6
votes
3answers
15k views

Load balancing & NAT-ing multiple ISP connections on Linux

I have two internet connections from two different ISPs and I need to balance the traffic originating to and from my network between the two ISPs. I am using Debian GNU/Linux. My set-up is like this ...
6
votes
1answer
920 views

How to traverse carrier-grade NAT (large-scale NAT) to reach VPN Server? [closed]

I currently run an OpenVPN Server via a home network connection that has a single, public, dynamic IPv4 address. My provider (AT&T U-Verse) will apparently soon switch to a large-scale NAT and ...
6
votes
2answers
610 views

Per-user routing doesn't seem to work

So, I'm trying to implement per-user routing so that I'm able to route all btpd torrent traffic over a VPN. Unfortunately, btpd does not currently allow you to bind to a specific IP address. :( I ...
6
votes
0answers
2k views

IPv6: the end of NAT? [duplicate]

Possible Duplicate: Switch to IPv6 and get rid of NAT? Are you kidding? Is NAT going to disappear with IPv6? What about during the "transition" from IPv4-IPv6? How are we all going to ...
5
votes
9answers
1k views

Do you think NAT is largely responsible for the delay in IPv6 adoption?

I'm wondering if this is really the case, or, if when IPv6 does get widespread adoption, we will still hide all the machines on a network behind a single (or few) IP address under the assumption that ...
5
votes
5answers
767 views

NAT as a firewall

Network Address Translation ( NAT ), seems to sort of act as a firewall for the hosts behind it because they are not available. Although I would never rely on this as my firewall, what are its ...
5
votes
3answers
4k views

Unable to connect on natted server from a host computer on the same LAN using public IP address

I have a server statically NAT’d using a registered IP address and it is accessible from the outside. The problem is I cannot access my server from the inside using the registered IP address with a ...
5
votes
7answers
17k views

Yum update not working on CentOS 6.2 minimal install

Note: This is my first question on the stack exchange network so please give mercy and provide guidance where needed. I have installed a CentOS 6.2 KVM guest and I am having problem getting yum to ...
5
votes
3answers
435 views

What's the best way to accomodate multiple devices that all want to use the same fixed IP address into the same LAN?

Suppose I have an ethernet capable device that has a hard coded IP address in it. I have software that works with the device, which could be configured to work with practically any IP address for the ...
5
votes
1answer
108 views

Running multiple services on different servers with IPv6 and a FQDN

One of the things NAT has permitted us to do in the past decade is split physical services onto different servers whilst hiding behind a single interface. For example, I have example.com behind a NAT ...
5
votes
2answers
1k views

How do I route a public IP range over an IPSEC VPN?

So, I have an established IPSec Site to Site tunnel. Site A has a SonicWall, Site B has a EdgeRouter. The first tunnel consists of Site A's NATed ips to Site B's NATed ips. Everything works as ...
5
votes
1answer
6k views

How do I assign a public IP to a machine behind a pfSense box using 1:1 NAT?

This should be dead simple but for the life of me, I can't get it working. I must be doing something stupid. I have a PFsense server with a public IP address. Behind it is three LAN segments: [ ...
5
votes
1answer
352 views

IPv6 and NAT, routing to multiple ISPs

Currently I have a nice setup using private IPv4 address space and uplinks from two ISPs to the Internet. Thanks to NAT I can just take down one of the interfaces and the Internet access is still ...
5
votes
2answers
6k views

Mikrotik and NAT/Routing issue

I have basic NAT/Routing problem with Mikrotik RB750 that I've been unable to solve over the past days. From our ISP we have 26 IP addresses: 10.10.10.192/27, with 10.10.10.193 being the gateway and ...
5
votes
1answer
1k views

How do you get AWS VPC EC2 instances to be able to see the AWS APIs?

We're spinning up infrastructure inside of an AWS VPC via CloudFormation. We're using auto-scaling groups to bring up VPC-EC2 instances (so, we don't bring up instances directly; ASGs manage that). ...
5
votes
1answer
374 views

Setting Up NAT Hairpinning to Connect to Site from an Internal IP Address

We use a WordPress plugin that checks for broken links. It uses cURL to do this. External links work fine but internal ones, not so much. The connection is refused. Talked to our host about this and ...
5
votes
1answer
111 views

Route traffic directly between nodes in a cluster

I apologize if this is a really dumb question. Objective Ensure that traffic that is meant to go between nodes in a cluster does not (inefficiently) go outside the cluster and then come back in, but ...
5
votes
2answers
1k views

TomatoUSB multiple IPs not forwarding

I am trying to use this Guide to enable multiple IPs on TomatoUSB. Our Firewall rules need to NAT and allow a 1to1 to two servers. /usr/sbin/ip addr add 208.x.x.133/30 dev vlan1 /usr/sbin/ip addr ...
4
votes
3answers
2k views

iptables nat does not exist

Today my iptables nat on the host system stopped working and I have no clue what happend! (That's very bad, I know) All commands are executed as root user. If I run $ iptables -t nat -L I get the ...
4
votes
4answers
2k views

Public Servers NATing?

My question in short: "Which is better? To assign private IP addresses to public servers and do NATing, or to assign public IP addresses to them without the need for NATing"? The NATing can be useful ...
4
votes
7answers
3k views

Why can't I connect to some ftp servers from behind my win2008 NAT?

I want to connect to an FTP server from my local network, which is behind a NAT. The gateway is a Win 2008 server, configured with routing and remote services / Nat enabled. The problem exists from ...
4
votes
3answers
464 views

LAN and WAN at the same cable?

Can I connect LAN and Internet using the same cable? LAN computers ------\ Ubuntu server ------Switch ADSL Router --------/ I want to make LAN computers 192.168.0.2-50, server will have real ...
4
votes
3answers
4k views

How to get VirtualBox NAT working with actual client IP's?

I'm using Virtualbox 4.0.10 on a Debian Squeeze box. I have a Windows 7 VM that I use to host a game server. After setting up NAT and port redirection, clients can connect to the VM, but the game ...
4
votes
3answers
7k views

Public static ip for vagrant box

I have server (Debian Squeeze) with 1 ethernet card and 2 public static IPs (188.120.245.4 and 188.120.244.5). What I want: Setup virtual box (Ubuntu) with access via static IP (188.120.244.5). ...
4
votes
2answers
2k views

Secure NAT setup with iptables

I have a Debian running device that needs to act as an internet-gateway. On top of that I want to provide a firewall that not only blocks inbound traffic, but also outbound traffic. And I figured ...
4
votes
2answers
2k views

NAT Reflection, or Split DNS?

I'm working on a network restructure that has three geographical locations, but will share some services. Two of the locations have workstations, and one has only servers (in a CoLo facility). We will ...
4
votes
4answers
830 views

faking NAT with a VMware distributed switch across multiple hosts

I need to construct a NAT for certain machines within the network. Wish to do this with dvSwitch - as it seems the logical way of attacking the problem as in this scenario there's just under 30 hosts. ...
4
votes
2answers
1k views

Where to find symmetric NAT?

Currently i'm working on some NAT traversal code (that allows to computers each behind it's own NAT to communicate with each other). But, surprisingly, i can't find any symmetric NAT's! (it's the most ...
4
votes
1answer
1k views

Load balancing SMTP in a way that doesn't hide the source IP address

I need to load balance SMTP to handle some applications that don't know how to use MX records. I set up a Netscaler using the TCP option on port 25 and now Exchange sees the source IP as that of the ...
4
votes
1answer
311 views

What is the difference between a web cache and a hierarchial cache server?

I'm trying to make sense of how to set up the simplest possible thing that could actually work at my office where we host events and have lots of people coming, potentially everyone downloading the ...
4
votes
3answers
6k views

Cisco ASA - NAT Reverse Path behavior

Recently ran into an issue where adding a dynamic NAT to an interface broke all translated traffic going through the interface with RPF failures. We found that the addition of the command caused NAT ...