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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Port Forwarding on Cisco Router

I'm a Cisco newbie, have the 1841, with two ethernet interfaces: interface FastEthernet0/0: Internal Desired destination IP: 186.67.181.140 interface FastEthernet0/1: External World IP ...
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158 views

KVM : domain names are resolved, but cannot ping

I've found that in KVM, my networking is acting funny. Oddly (1) I can resolve external internet locations using nslookup or ping , but I cannot actually receive a ping back. (2) I cannot ping ...
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70 views

ifconfig TX/RX on gateway

I have a linux gateway which does nat for a couple of machines behind it. I got complains that we have way more monthly traffic gigs more than we should so the first thing I look was check the ...
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122 views

Is it advisable to use virtual Linux server installed on i5 / 8GB / 500GB desktop class computer? [closed]

We have CentOS 4.3 P4 / 512MB /Linux server installed somewhere in 2006-7. This machine has three network interaces for leased line, broadband (backup) and LAN. We use Sendmail, Fetchmail, NAT, Squid, ...
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381 views

postfix - connection refused from behind NAT

When attempting to telnet postfix from a different host in the same LAN through the FQDN (and thus the LAN's public IP), the following error occurs: root@mailer:/var/log# telnet mail.domain.com 25 ...
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417 views

Trouble with port 80 nating (XenServer to WebServer VM)

I have a rent server running XenServer 6.2 I only have 1 public IP so i did some NAT to redirect ports 22 and 80 to my WebServer VM. I have a problem with the port 80 redirection. When i use this ...
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482 views

Iptables prerouting based on destination's DNS name?

I've got a question concerning iptable prerouting. I'm not that familiar with networking/routing/iptables so I hope this is not a stupid question, at all. So I ask for your understanding and ...
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454 views

UDP packets are not reaching iptables NAT table

I'm trying to redirect UDP incoming packets to port 4000 to another IP with iptables: iptables -t nat -A PREROUTING -p udp --dport 4000 -j DNAT --to-destination 192.168.100.20 Unfortunately they ...
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Allowing a private subnet EC2 access to the internet - Amazon AWS

I have a VPC "VPC with Public and Private Subnets" created via the VPC wizard which should include NAT for the private subnet VPCs however it's not working. They are unable to browse the internet, ...
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41 views

Using NAT with iptables between corporate network and firewall'd corporate network

At work we have a firewall between two networks. I was told they opened up the two ports for me but I needed to modify the IPtables to allow packets to go through. I'm not familiar with the correct ...
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92 views

Listening “through” GRE Tunnel

Currently I'm looking to learn about using GRE Tunnels and I have the following scheme: Server1 (200.1.2.3) ----> Server2 (190.1.2.3) Both servers have public IPs Then I've setup a GRE Tunnel with ...
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412 views

Cisco router: expired translations not timing out

Why would a Cisco router stop removing expired translations from the NAT table? For example: #show ip nat translations tcp verbose tcp <loopback>:60576 <inside>:60576 ...
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510 views

Port Forwarding to a VPN Client

I'm looking for some help getting a port forward setup to a VM running Ubuntu 12.04 on my LAN. I can forward the port to the VM successfully and connect to the service over the Internet. But when I ...
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2answers
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OpenVPN tun routing (can ping tun interfaces) with mikrotik and NAT on both ends

Problem The Mikrotik site is unable to ping anything on the server site. The Server site is less important right now. OpenVPN Server config is on LINUX port 1194 proto tcp dev tun ca ca.crt cert ...
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93 views

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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127 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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79 views

NAT answers instead of remote host

Currently I have VPN client access set up on OpenSuSE 13.1 server to third-party remote Cisco VPN IPSec server. VPN Server is set up to provide access for a host only and to provide access for a local ...
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642 views

pfSense NAT routing using VLANs

We already have pfSense installed and it is working for our single IP address on 1.1.1.1. We also have a further 3 ip addresses (1.1.1.2, 1.1.1.3, 1.1.1.4) which are set up as VLANs on the WAN ...
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151 views

Firewall setup Huawei 4G with DMZ

Network topology: ISP1 | | Alternative ISP 4G | | | Huawei 4G with DMZ | | ...
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1answer
693 views

Cisco 887VA Port Forwarding Not Working

I have a Cisco 887VA connected to our BT Business Broadband line. We also have another modem on a seperate connection which also handles our DHCP. The Cisco is plugged into our network switch, as is ...
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500 views

FreeBSD jail with IPFW with loopback - unable to connect loopback interface

I am trying to configure a one IP jail with loopback interface, but I am unsure how to configure the IPFW rules to allow traffic to pass between the jail and the network card on the server. I have ...
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134 views

Weird socket behavior in VirtualBox (NAT + PAT)?

I have a Linux VM with NAT and PAT configured. Let's say ports 2000 and 2001 are forwarded to the VM. These ports are also configured for external access on a device such as a router using a domain ...
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125 views

2 NIC vs NAT for exposing server

I'm trying to virtualize some applciation using citrix. so I have to expose the secure gateway to Internet (put it in DMZ). my question is which is better practice ? 1 - using 2 physical NIC, one ...
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113 views

can I use DNS with private NAT addresses?

I want to build a service that dynamically creates VMs and assigns each VM a public DNS record which could be a full domain or a subdomain. Assume the VMS all live on a single host. The VMs will have ...
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51 views

Poor large transfers behind NAT on Centos

I have the following set up. A Centos 6.5 VM running on an ESX host, with a public IP4 address. It is acting as a gateway for (a bunch of) other Centos 6.5 VMs that are only connected to a virtual ...
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NAT444 on vodafone 3g [closed]

I am using Huawei K3765 with vodafone as ISP. When i tested my IP with ipconfig, private IP is assigned to me. I dont think this device act as a router, since its just a 3g donle. This created the ...
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[SOLVED ]Openvpn routing for lan to lan through tun

I am trying to setup an OpenVPN tun to connect two lan's The open vpn connection is up and working but there is a problem with my routing or nat or something. What I need is an example of what a ...
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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 ...
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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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Websever behind Sonicwall, Gateway Timeout

I am stuck here, I have a Cradlepoint CBA750B in IP-passthrough mode connected to x1 on my Sonicwall NSA220. Behind the Sonicwall I have a webserver on the LAN. I have X1 set to use DHCP to get the ...
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873 views

How accessing a NATed, virtualized (LXC) server over public IP from client itself on a bridged network?

Setup ____________________________ ____________________________ | Host | | Client | | Public IP: 66.66.66.66 | ...
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169 views

Redirect traffic from one server to something.cloudapp.net (CNAME) [closed]

Through out North America, we have lots of legacy devices, which sends data to our server which has static IP Address. Now we are moving to Azure cloud services, and as you know they do not guarantee ...
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165 views

Firewall and NAT settings in GSM modem for one server

I have a GSM Modem (PSI-MODEM-GSM/ETH) in field with one device behind, acting as a server. The situation is as follows: "PC" | \_________Dynamic IP: 10.103.153.122 | ...
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362 views

CISCO: conditional port-based NAT (policy-based PAT)?

I have a problem to nat-translate inbound http packets to different local_ips based on some condition (like dscp bits set). Actually the dscp bits get set on the incoming trafic using NBAR. I hope ...
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187 views

Communicating between two servers sitting behind their respective NATs

I'm building an web app (Server A) that communicates with a remote server (Server B) that is connected to the internet. Server B resides behind a NAT and is listening to communication on 3 ...
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1answer
170 views

iptables NAT table not matching anything [duplicate]

I am attempting to take a TCP service running on port 1234, and make it appear as if it's running on port 81. I thought the following might do it: iptables -A PREROUTING -t nat -p tcp --dport 81 -j ...
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127 views

Software for emulating networks and NAT

I am working on a software that I need to test with different types of NAT, and I would like to set up a test environment I can reconfigure in different NAT modes. I would like to have: ...
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80 views

How to avoid hairpin VPN on cisco

I currently have a hairpin VPN setup with a Cisco ASA, but I'm not very happy as it messes up service access that are on ASA external IP address and are NAT'ed inwards :( How should I re-design the ...
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108 views

iptables NAT forward range

I have two network interfaces, eth0 and eth1. eth0 has a public ip, eth1 has 172.16.0.254/24. I'd like to do the following mapping: 172.16.0.1:22 -> eth0's public ip:2001 172.16.0.2:22 -> ...
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209 views

Iptables/ufw - blocking ports when using nat

I use NAT to move requests from external ports to an internal ip address and port hosted with proxmox. Something like this: iptables -t nat -A PREROUTING -i vmbr0 -p tcp --dport 8000 -j DNAT --to ...
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1answer
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iptables forwarding through virtual interfaces

I'm trying to configure my computer as a gateway between two networks, but I cannot make it working for some reasons Here is a representation of the network: 192.168.1.101 192.168.1.102 ...
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199 views

access same subnet on different interfaces

I have a router with external (WAN connection) subnet 192.168.1.0/24 and also on same router a tunnel to a remote location which have the exact same subnet (192.168.1.0/24), and i need from my LAN to ...
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144 views

strongswan packet get natted when ufw is enabled

I'm using strongswan 4.6.4 to connect road warriors to my server (ubuntu 13.10), which is natted behind a firewall. left=%defaultroute leftsubnet=10.10.1.0/24 right=%any ...
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Dead-simple Juniper firewall hairpinning [closed]

I have a SRX100 firewall running JunOS 12.1. I have a WAN interface proxy ARPing ten or so static routable IPs. I have a LAN interface on a simple class-C subnet (we'll call it 192.168.0.x). I'm using ...
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OpenVPN running on Internet Gateway, so all private clients can access VPN with no config

Our LAN connects to our office gateway machine (192.168.1.1), which is connected to the Internet. I have setup NAT/Masquerading for this purpose with no issue. We also use OpenVPN to connect to our ...
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1answer
217 views

Access Apache VirtualHost from localhost

I have a DirectAdmin setup with Apache on a server which is behind NAT. Everything is working correctly when accessing a VirtualHost from outside the machine (either through the Internet and the ...
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195 views

FreeBSD ipnat(8) rdr - not redirecting

I'm using FreeBSD-10.0-RELEASE: root@fx:~ # uname -a FreeBSD fx.alexus.org 10.0-RELEASE FreeBSD 10.0-RELEASE #0 r260789: Thu Jan 16 22:34:59 UTC 2014 ...
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67 views

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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244 views

how to forward proxy requests using iptables

I've this schenario ----------------- ---------------- ---------- | SERVER A | ---(port:2128)> | PROXY | ---> | INTERNET | | (10.30.1.1) | ...