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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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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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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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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How can I NAT traffic for one VPN to come from a different IP on Cisco ASA?

I have a Cisco ASA firewall between our private network (10.1.0.0/16) and the outside world, and multiple VPNS going to client sites. Existing: [10.1.0.2...] = source client | [10.1.0.1 ASA ...
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tcpdump not picking up traffic redirected by iptables

The following iptables rule is used to redirect all internet traffic coming in from eth1 to port 3000 at localhost (interface lo with ip 127.0.0.1): iptables -t nat -A PREROUTING -i eth1 -p tcp ...
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845 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 ...
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1answer
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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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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
173 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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694 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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1answer
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How to access Apache virtual-host in VMware guest through NAT?

As a webdeveloper I have an Apache server running on my local machine which I use for developing. The server is listening on every IP address on port 80 as per default. However I've used the ...
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167 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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3answers
5k 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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2answers
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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
386 views

Iptables does not seem to be applying SNAT to packets sent on a raw socket

I'm sending packets from a user space program to my wireless interface wlan0. I've set up a SNAT rule with iptables as follows iptables -t nat -A POSTROUTING -o wlan0 -j SNAT --to 192.168.1.3 And ...
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2answers
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libvirt and network filtering with nat - iptables overrides

At first, I want to say: I know, it was done initially wrong and I want to avoid doing everything again from the scratch because of general downtime. I am running libvirt/KVM on RHEL. I've got VM ...
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2answers
728 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
746 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
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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
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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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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
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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 ...
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1answer
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Does hole punching require a UDP rendezvous server Or could it be a TCP one?

I'm trying to get my head wrap around this issue... I would like to connect two users... Those users are already connected to a TCP server, which is aware of both public ip and connection TCP port. ...
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Iptables: Forwarding packets doesn't work

I have 3 Linux Systems A, B and C. A is a TCP Client and sends a message to TCP Server on C. A can see only the external IP of B which is at wlan0 interface, 192.168.0.3 ------------------ ...
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307 views

NAT setup for an SIP Registrar/Proxy

I am currently trying to get the following scenario to work. Warning: I am a software engineer--not a network admin. I have various SIP endpoints (sip based video servers) on a LAN. On a Windows ...
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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 ...
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1answer
591 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
574 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
353 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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iptables nat: Handle OUTPUT chain via PREROUTING chain / forward from OUTPUT to PREROUTING

I would like to automatically handle packets in the OUTPUT chain of the NAT table (which are generated locally) like if they come from outside (via PREROUTING). Is is possible to use a "forward ...
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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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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
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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 ...
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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 ...
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340 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 ...
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Route-Map vs ACL for Cisco NAT

Is there pros and cons of using route-maps vs access-lists for network address translation on a cisco router?
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NAT GRE (IP protocol 47) over Linux router

I have a host that has a permanent static GRE tunnel to a server on the Internet. Right now the host has its own real IP address. I want to put the host behind a Linux box (Smoothwall), and assign it ...
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1answer
60 views

ProFTPD IP masquerade just some ways

I am trying to setup a FTP server using ProFTPD on Xubuntu 15.10. Users will connect to this server in two ways: internally (using an internal IPv4 address) externally (using domain name pointed to ...
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1answer
63 views

DHCP Server with 2 nics

I have windows 2008 r2 x64 enterprise server with a domain. That server has 2 NIC nic1 which is connected to a router nic2 - here i need 1) run dhcp for private LAN 2) forward internet connection ...
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1answer
178 views

pfSense can't access https website

I have just installed pfSense on a PC Engines APU1D4 to evaluate as an alternative to a Soekris 5501 + OpenBSD based setup, I have a PPPoE WAN configuration. The pf rules, NAT and PPPoE ...
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2answers
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Trying to connect to servers in a remote lan with softether vpn client and iptables nat ip_forwarding

I have implemented a softether vpn server on one aws server connected to other instances in a LAN. I can ssh into the server with ssh myname@10.0.1.10 without problem. I followed this guide My goal ...
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1answer
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Iptables udp port forwarding [duplicate]

I'm using latest debian relese and i need to do some port forwarding, but i dont know how.I have 2 stream sources coming to my server on the same udp port from 2 diferent ip-s 192.168.1.2:1003 via ...
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2answers
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Exposing private network ip

I have the following setup: Box A eth0 - 192.168.1.101 eth1 - 10.10.2.1 Box B eth0 - 10.10.2.2 Box A has internet access through eth0. I want Box B to be visible on the 192.168.1.0/24 network, so ...
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259 views

Stateless NAT with CentOS 6

I'm looking to set up the following: ---[IVR 1] | (internet)----[CentOS box]---+---[IVR 2] | ...
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1answer
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Routing DHCP traffic over the internet

i'd like to know if it's possible for the internet to be between a DHCP server and the network it's "assigned" to? so basically, something like this: -------------- ------------- ...
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1answer
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Routing between 2 different subnets on 2 different interfaces in SonicOS

I'm having a bit of a problem allowing traffic between two of my subnets. Here's the structure I've built. The X0 interface has our windows server on it and it handles DHCP/DNS, etc. X1 has the WAN ...
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1answer
186 views

Can I use NAT64 to route public IPV6 traffic to internal IPV4?

I have a bunch of public IPv6 addresses and some services that run IPv4 only. Can I use NAT64 to connect these services? Is there another solution like a proxy or something?
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1answer
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Should we accomodate a customer asking us to NAT servers behind new PUBLIC IPs within a VPN?

We're a SaaS provider, setting up a IPSec VPN between our data center and a customer's site so they can directly access their hosted database server from their LAN. Instead of exposing our internal ...
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1answer
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How to set mark on packet when forwarding it in nat prerouting table?

I have a few port forward rules like this iptables -t nat -A PREROUTING -p tcp --dport 46000 -j DNAT --to-destination 172.16.8.2:46000 iptables -A FORWARD -p tcp -d 172.16.8.2 --dport 46000 -j ACCEPT ...
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633 views

can't find a way to forward in iptables for specific mac address

I use a linux Centos 6.3 as an Internet gateway with NAT. I want to allow a specific host to have access to Internet, but I don't want to use its IP address since it may get a new IP address from the ...