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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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 ...
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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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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 ...
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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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393 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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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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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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Forward differing hostnames to different internal IPs through NAT router

I have one public IP address, one router and multiple servers behind the router. I would like to forward differing domains (All using HTTP) through the router to different servers. For example: ...
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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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Are DNAT and REDIRECT equivalent when applied to locally destined traffic?

In setting up our OpenStack environment, I ran into a problem that was preventing instances from contacting a server running on the host. The metadata service (which exposes an HTTP API) runs on port ...
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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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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: ...
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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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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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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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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: ...
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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 ...
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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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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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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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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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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 ...
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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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Authorative DNS behind NAT possible?

I am currently running an authorative Bind9 DNS server for a bunch of domains. This authorative server currently replicates to a couple of slaves which are then used to meet the subnet requirement for ...
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Passive mode for FileZilla FTP isn't working

We have FileZilla server 0.9.37 running on Windows server 2008 R2 Active mode works OK, The Windows firewall on the server is off. Our Router is a DrayTek vigor 2820. Under NAT, Open Ports, I have ...
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How can I port forward over a VPN NAT?

I have a multi-site VPN currently running with pfSense boxes and currently using OpenVPN. However I can change the OS and VPN type if need be. The main router has a 10.13.0.0/16 subnet and a series ...
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Virtualbox, slow upload speed using nat

Im running Virtualbox on a Ubuntu 12.04 server (host) and I'm running a Windows 7 as guest os. Im using the (virtual) Intel PRO/1000 MT network card. I get good network performance for download ...
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Advice regarding resilient internet access from within an Amazon VPC

We've had our NAT server fail 3 times thus far - once due to an issue with it's EIP and twice due to it's host being CPU bound. While I understand these things happen, we can't afford to keep taking ...
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Accessing the DNAT'ted webserver from inside the LAN

I have a small network with a router, which maintains a connection to Internet, a server and some workstations in a local network. Server is meant to be accessed from the Internet, and there are ...
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Exposing a WebServer behind a firewall without Port Forwarding

We are deploying web applications in java using tomcat on client machines across the country. Once they are installed, we want to allow a remote access to these web applications through a central ...
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244 views

Router limits network performance but its CPU load isn't 100%

I'm using a PC Engines APU device running FreeBSD as a NAT router. The setup is very usual: one WAN connection and one LAN connection. Theoretically, WAN connection is 800/40 Mbit/s and the LAN one ...
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Symmetric NAT and UDP Hole Punching

I've read this question, but the explanation of Symmetric NAT wasn't detailed enough. Please could someone help me to understand the following paragraphs? I read this about Symmetric NAT: Each ...
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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. ...
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759 views

How do IPv4 only applications work on IPv6 only hosts?

Is there any way for IPv6-unaware applications to continue to work on a host with only IPv6 connectivity? The IPv4 implementation of the host could know about the problem and just encapsulate the ...
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Multiple web servers in a IIS web farm behind a single IP address

I have 4 web servers (Windows Server 2008 R2) and just one public IP address. They all need to be a part of web farm (so the requests for the site are spread over all servers). Two questions: 1) Is ...
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Do NATs verify the source port of a SYN received after a SYN has been sent?

I'm unsure of whether this question is more appropriate for stackoverflow or serverfault. If you think it's more suited for stackoverflow, let me know and I'll delete this and move it over. I have a ...
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Service can't connect to self using public IP, NAT problem

I have a dedicated server from serverloft.eu, but due to some network security I cannot use bridge networking on my server. So I have setup all my IPs to the main eth0, and used NAT to forward trafic ...
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Create NAT rule and security policies for port 443/80 on a Cisco ASA 5510

I've been trying to setup NAT and give access to a public IP address to my local network, I just can't get it to work. It's my first time using a Cisco firewall. Thanks for your help!
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Connect to Teredo-enabled server behind NAT

I've got a Vista64 machine behind a NAT router connected to the IPv4 Internet. Teredo is enabled on my machine and I've got a IPv6 address with 2001:0: prefix. I can ping several servers in the IPv6 ...
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Amazon EC2 VPC: NAT instance download speed performance drop

I have a set of servers inside Amazon EC2 in VPC. Inside this VPC I have a private subnet and a public subnet. In the public subnet I have set up a NAT machine on a t2.micro instance that basically ...
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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
976 views

Dual Cisco Router Stateful Firewall

At my company we have a single Cisco 3925sec/k9 router running BGP with 2 ISPs. Now we want to purchase a redundant router of the same model to eliminate a single point of failure. I can set up BGP ...
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Can I enable NAT on a Cisco ASA without breaking connectivity?

Sorry for the noob question, I haven't done this in years... I have a Cisco ASA with a working VPN, which I set up like five years ago, and I would like to forward http through to an internal IP ...
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What is the motivation for DNS64?

I'm wondering why NAT64 needs something like DNS64 at all. Couldn't an IPv6-only host, when trying to reach an IPv4-only host, just embed the IPv4 address of the target host in an IPv6 packet (by ...
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Traffic blocked between VLANs despite security-level difference on ASA 5510

I have an Cisco ASA 5510 configured thus: interface Ethernet0/0 description ### Trunk for inside, wlan ### speed 1000 no nameif no security-level no ip address interface Ethernet0/0.10 ...
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Windows 7 with internal port redirection, is it possible?

I received a request from one of our developers that I am having trouble solving. Here in the office they use linux desktops and I can forward the localhost:80 via a iptables nat to localhost:8080. ...
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Vigor 2820 Router -Port Forward Not Working

We are trying to solve what should be a trivial problem! We have a DrayTek Vigor 2820 series ADSL router/firewall and we need to forward port 80 to a web-server. The box is connected to it's adsl ...
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Connecting a physical ethernet port to a VMware virtual switch?

I hope this is the correct place for this question. I thought about posting it to Super User first, but it seems to be more relevant to this place. Anyway, here goes: I need to connect a device ...