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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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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375 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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1answer
255 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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343 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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3answers
6k views

Setting up VMWare ESXi 5 with a single physical NIC

I have a cheap but powerful dedicated server I am leasing with OVH, because they were recently having a promotion. I would like to try and manage all this power by playing with VMs using ESXi. ...
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1answer
815 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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39 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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74 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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235 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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473 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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1answer
75 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
3k views

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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1answer
100 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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58 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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1answer
123 views

Firewall setup Huawei 4G with DMZ

Network topology: ISP1 | | Alternative ISP 4G | | | Huawei 4G with DMZ | | ...
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460 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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89 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
88 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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65 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
103 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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0answers
49 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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62 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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67 views

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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1answer
1k views

Hyper-V VM Lab + RRAS + RDP

My background is primarily .NET Development with some System Administration skills. I'm trying to set up a VM Lab for me to test System Applications I'm developing but I've only ever done System ...
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0answers
4k 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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Mikrotik and NAT/Routing issue

I have basic NAT/Routing problem with Mikrotik RB750 that I've been unable to solve over the past days. From our ISP we have 26 IP addresses: 10.10.10.192/27, with 10.10.10.193 being the gateway and ...
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33 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
1k views

Why won't vyatta allow SMTP through my firewall?

I am setting up a vyatta router on VMware ESXi, But I see to have hit a major snag, I could not get my firewall and NAT to work correctly. I am not sure what was wrong with NAT but it "seems" to be ...
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1answer
475 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
73 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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1answer
552 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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2answers
235 views

Configure VirtualBox webserver to see visitors IP address

I finally managed to move my server to VirtualBox virtual machine. VM is running in NAT mode. I have forwarded necessary ports, including the port 80 which I first fowarded with iptables to port ...
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1answer
118 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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633 views

Cisco 881 losing NAT NVI translation config after reload

This is a weird one, so I'll try to explain in as much detail as I can so I'm giving the whole picture. As I've mentioned in my other questions, I'm in the process of setting up a new Cisco 881 as my ...
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1answer
812 views

Reverse NAT Setup for Hyper-V on Win 2008 R2

I'm trying to setup a Linux server behind a Windows Hyper-V host that will help supply some of the services (SSH, HTTPS, etc). However getting RRAS configured for reverse NAT (port forwarding) turned ...
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1answer
186 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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0answers
106 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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2answers
119 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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3answers
3k views

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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1answer
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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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3answers
1k views

Iptables massive 1:1 NAT

I have to connect two LANs: LAN1: 10.10.0.0/16 and LAN2: 192.168.0.0/16. I can't do simple routing, because 192.168.0.0/16 net is prohibited in LAN1, so I am thinking of using Full cone nat (1:1) to ...
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1answer
81 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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1answer
64 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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1answer
67 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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1answer
162 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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33 views

Is it possible to hairpin on Cisco 851W IOS 12.4(15)T9 and how?

I need machines on the LAN to be able to access by the external address or hostname. If it can't be done, then just by hostname is OK as well, so I thought of just doing it through DNS on our internal ...
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3answers
16k views

Load balancing & NAT-ing multiple ISP connections on Linux

I have two internet connections from two different ISPs and I need to balance the traffic originating to and from my network between the two ISPs. I am using Debian GNU/Linux. My set-up is like this ...
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1answer
651 views

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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2answers
6k views

Inbound SIP calls through Cisco 881 NAT hang up after a few seconds

I've recently moved to a Cisco 881 router for my WAN link. I was previously using a Cisco Linksys WAG320N as my modem/router/WiFi AP/NAT firewall. The WAG320N is now running in bridged mode, so it's ...
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1answer
166 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 ...