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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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 ...
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873 views

pf (Mac OS X) rule to redirect all traffic to a specific ip/port

I'm trying to recreate this iptables setup (from https://github.com/darkk/redsocks) with pf: iptables -t nat -A REDSOCKS -p tcp -d 10.0.0.0/8 -j REDIRECT --to-ports 12345 iptables -t nat -A OUTPUT -p ...
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How do you NAT Hairpin in IOS 8.3+

As I asked here and duplicated here it appears NAT Hairpinning is the answer I'm looking for to allow internal servers to loopback through the ASA to access external IP's (without using DNS Doctoring)....
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public ip resolves externally but not internally

I have a one to one NAT on pfsense that assigns a public IP to an internal IP (running a web server). When I open the public IP from an internal machine, it will not resolve to the internal IP, ...
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1answer
470 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 ...
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173 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 ...
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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 ...
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Iptables NAT logging

I have a box setup as a router using Iptables (masquerade), logging all network traffic. The problem: Connections from LAN IPs to WAN show fine, i.e. SRC=192.168.32.10 -> DST=60.242.67.190 but for ...
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838 views

Windows Server 2003 IPSec Tunnel Connected, But Not Working (Possibly NAT/RRAS Related)

Configuration I have setup a "raw" IPSec tunnel between a Windows Server 2003 (SBS) machine and a Netgear FVG318 according to the instructions in Microsoft KB816514. The configuration is as follows (...
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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 ...
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Cisco - NAT causes nslookup to return local IP

A little background: I have a server on my LAN that is statically NAT'd to its public IP in my Cisco 871. The rest of the same local subnet is statically NAT'd to a different Public IP, in order to ...
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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 ...
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Ping: sendmsg: operation not permitted error after installing iptables on Arch GNU/Linux

Yesterday I got a new computer as my homeserver, a HP Proliant Microserver. Installed Arch Linux on it, with kernel version 3.2.12. After installing iptables (1.4.12.2 - the current version AFAIK) ...
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3answers
563 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 ...
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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 ...
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FTP - 500 I won't open a connection to xx.xx.xx.xx

I'm running a server on AWS and I'm connecting out to a partner's FTP site (not much idea what they are running). My server has an elastic IP. In the results below xx.xx.xx.xx is the internal IP (...
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1answer
3k views

pfSense router on a LAN with two gateways

I have a LAN with an ADSL modem/router on it. We have just gained an alternative high-speed internet connection at our location, and I want to connect the LAN to it, eventually dropping the ADSL. I'...
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2k views

Linux IPv6 Transparent Proxy (but Linux doesn't support NAT on IPv6!?)

On Linux I can make a transparent proxy simply by adding a iptables -j REDIRECT command. To my surprise, I am needing to support IPv6. Simple enough right? iptables6 -j REDIRECT command not supported!...
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1answer
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Need to duplicate UDP packets to multiple destinations via iptables

I'm looking to duplicate UDP traffic for SYSLOG and NetFlow data and was hoping to use iptables to do so, but so far I'm not having much luck. I'm aware of other user space software packages that can ...
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4answers
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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. ...
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2answers
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How do I forward/NAT all traffic to one interface/IP to a remote IP?

I have one "server A" that has multiple IPs attached to it, like so: eth0:0 1.1.1.1 eth0:1 1.1.1.2 eth0:2 1.1.1.3 I have another "server B" that also has multiple IPs attached to it, like so: eth0:...
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1answer
4k 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 ...
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1answer
518 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 ...
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3answers
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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 ...
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1answer
492 views

Forwarding a port on the loopback interface to a remote IP/port

I have two Docker containers that I'm trying to network together in a specific way. Container A is running a Redis server on port 6379. Container B is running an interactive shell and needs to access ...
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3answers
2k views

Internet access from private VPC subnet?

My brain is a little bit fried trying to figure this out but I can't seem to get private subnets to connect to the internet to grab updates for example. Basically all I want is web access for these ...
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1answer
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DNS Server Behind NAT

I've got a Bind 9 DNS server sitting behind a NAT firewall, assume the Internet facing IP is 1.2.3.4 There are no restrictions on outgoing traffic, and port 53 (TCP/UDP) is forwarded from 1.2.3.4 to ...
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Remote access to internal machine (ssh port-forwarding)

I have a server (serv05) at work with a public ip, hosting two KVM guests - vtest1 & vtest2 - in two different private network - 192.168.122.0 & 192.168.100.0 - respectively, this way: [root@...
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2answers
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fwbuilder: Port forwarding works from outside, but not inside

I'm hoping there's something obvious I've missed here. I have NAT rules set up to forward a few different ports to an internal machine. When a request comes in from the internet, everything works as ...
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2answers
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fwbuilder: port forwarding incoming 222 port requests to a local machine 22 port

I am using fwbuilder to setup my iptables rules for a public server. The idea is to forward external requests from the 222 port to a local machine's ssh port. The settings i used are: NAT section ...
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NAT routing and port forwarding on Cisco ASA 5505

I have inherited my first Cisco router and am having trouble understanding how to do NAT port forwarding correctly. ASA: 8.0.2 ASDM: 6.1(1) I have a single external ip address on the outside (via ...
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KVM Guest with NAT + Bridged networking

I currently have a few KVM Guests on a dedicated server with bridged networking (this works) and i can successfully ping the outside ips i assign via ifconfig (in the guest). However, due to the ...
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3answers
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How do I configure my router under another to avoid NAT issues?

I'm sorry if this has been answered before; I tried looking but couldn't find a solution. I'll try and explain as clearly as I can. I've recently purchased a Rogers Mobile Rocket Hub and it's ...
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2answers
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How do I stop the natd log spam on Mac OS X with Internet Sharing?

I have InternetSharing enabled on my Mac (Leopard), so that my iPhone can get access to the internet in a wireless environment. Every second or so, I get the following error sent to system.log: 7/2/...
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1answer
196 views

Finding google unusual traffic

We are a small Internet provider. In order to get Internet access we are using NAT (10-20 users per one public IP). And lately we've met with Google blocking services (captcha and full block) and we ...
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Why would you internally use NAT? [closed]

I work at a fairly huge company as a software engineer and I would like to understand why an enterprise would internally use NAT. We have several data centers, somewhat geographically close to each ...
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1answer
318 views

Multi homed firewall with ipnat

i am trying (without success) to configure a ipnat/ipf box under FreeBSD 8.2, here is the scenario: outside inside +----+ ADSL 1.2.3.0/...
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NAT64 configuration with tayga on Debian 6

I'm trying to implement NAT64 with tayga on my server and came to a point where I'm not sure how to proceed. My server is connected via one IPv4 address and one /64 IPv6 address block to the internet....
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port redirection on solaris 11

I'm trying port forwarding on solaris 11. I have a mechine behind a server that use solaris 11. I try to access that mechine from the external port, and forwarded by solaris 11 mechine to that machine ...
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4answers
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Can a global IPv6 address be NAT'd to an internal IPv4 address at a firewall-level?

As an organisation we've just requested our first IPv6 allocation. At present we are a wholly IPv4 organisation with a global IPv4 address allocation configured on our edge router and used (...
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1answer
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Why Are There Only 65,535 Ports, and Will We Ever Have More? [closed]

I understand the original reasoning behind having 65,535 ports per IP address: this is the highest number that can be represented by a 16-bit, or 2-byte, number, and it wasn't conceivable that ...
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2answers
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Why is nat required when proxy is enough? [closed]

My machine is connected in a local lan. to connect to the internet the traffic goes through proxy server. my understanding of proxy server is that it sends the request on behalf of the original ...
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3answers
201 views

How widespread is double (or more) NAT/PAT?

Background: I'm working on a hole punching service with UDP, and in order to differentiate users under the same public IP, I've thought of making the user also send their local IP. That way, I killed ...
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3answers
6k views

How many valid NAT mappings can a common NAT support?

How many NAT mapping rules (that is, mappings between internal, private IP:PORT, and externally mapped IP:PORT) can a common NAT box support? Is there a limit in such number (that is, how many rules ...
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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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Advanced routing problem

I have 2 internet links using 2 ADSL routers and I need to give access to the Internet for the 192.168.0.0/24 network. I have to route outgoing traffic based on port number, protocol, … using ...
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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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1answer
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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
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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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5answers
451 views

Isn't NAT a MUST when a LAN uses rfc 1918 private IPs?

Isn't NAT a MUST when a LAN uses rfc 1918 private IPs? Can an organization assign its hosts with private IPs and still communicate with the external world without NAT? how can an internal host with a ...