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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Change sender-IP for VM in libvirt behind NAT

I have a server with my own public /28 IPv4 Network. On this server I have some vServers, done with KVM/libvirt. These vServers are connected with a virtual network, NATed to the internet. Every ...
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72 views

Packets are not routed by iptables, how to debug

I'm using OpenStack and OVS. This is my case: From a remote host, I ping VM with IP A. Local gateway received the echo request, then send a packet with IP A and MAC address A' (based on a fixed ...
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43 views

Simple MASQUERADE NAT between 2 VM

I'm on a cloud service and I'm trying to set up NAT between two VM. I've never experienced issues in this simple step, but this time is different and I'm near to give up. The first VM had two ...
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1answer
408 views

Can't establish a reliable VPN tunnel (ShrewSoft client / ZyWALL USG-50 firewall)

I try to setup an IPSec VPN tunnel through my firewall (ZyWall USG-50), but it doesn't work like it should. quick scheme of my installation: ME [A.B.C.D] --- **INTERNET** | ...
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3answers
86 views

Packages drop when using iptables NAT

We are using NAT made with iptables. However when there are lots of connections (or sessions) through NAT server packages start to drop. There is no log in syslog etc. I think this is caused by sysctl ...
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28 views

Does it seem from NAT when they really come through a proxy?

Just question. When a client really come through a proxy, can we tell it from being through NAT?
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1answer
609 views

How to Configure Source NAT (Private IP => Public IP Outbound)

I'm running VMWare ESXi Free and have Zentyal SBS 3.2 running as a Gateway. I have 5 Public IPS (CIDR/29, let's call them 69.1.1.1 - 69.1.1.5) and currently Zentyal is bound to 69.1.1.1 as the ...
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58 views

Assign internal IP address based on subdomain

I have a domain name, let's say foo.com. I have a server which has a public IP (Server-A). I also have a lot of servers (Server-B, Server-C, Server-D etc) which are all connected in a private network ...
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70 views

Cisco ASA Access anyconnect from inside IPsec tunnel

I have a Cisco ASA on a dynamic WAN IP with a IPsec site-to-site tunnel to a remote linux host in a datacenter with a static WAN IP. All non local traffic is tunneled and the datacenter end is the ...
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99 views

Cisco ASA 5505: PAT / NAT between 2 IPSec Tunnels

I've the following Setup: Customer <-> HQ <-> Branchoffice The Customer has a 192.168.1.0/24 subnet. On the HQ only the VPN Gateway is in my context, 172.20.10.1 . And on the Branchoffice ...
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Linux routing: How to allow a device inside private network to connect a public IP over an unknown network?

Consider following network topology: ---------- ---- (my network) ---- | Device 1 | (.101) | 192.168.191.0/24 | ---------- | | ...
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134 views

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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71 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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1answer
43 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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1answer
93 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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196 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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1answer
155 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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1answer
125 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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241 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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1answer
383 views

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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35 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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49 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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141 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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408 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
1k views

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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1answer
71 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
437 views

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
92 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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50 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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300 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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102 views

Firewall setup Huawei 4G with DMZ

Network topology: ISP1 | | Alternative ISP 4G | | | Huawei 4G with DMZ | | ...
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1answer
217 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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1answer
242 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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56 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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1answer
59 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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54 views

With split routing configuration returning packets don't reach their sender

I am trying to configure a split routing setup, where all traffic goes out the default eth0 interface, while packets from a single client are routed via tun11 (OpenVPN interface). So far I've come up ...
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1answer
95 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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47 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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1answer
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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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47 views

Is there an optimal NAT configuration in Cisco IOS for peer to peer applications?

The Cisco router in my organisation is set up to use Port Address Translation (PAT) for Internet connectivity. ie All outbound internet connections are from the ip address or the border Cisco ...
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1k views

[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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3answers
4k 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 ...
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25 views

Impact of iodined settings to server

I would like to install iodined, the IP tunnel via DNS, on a working web server. However, the configuration requires to set IP forwarding add NAT masquerading rules to iptables (and open DNS port) ...
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1answer
211 views

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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1answer
58 views

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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335 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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93 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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86 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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1answer
101 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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2answers
80 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 ...