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.

learn more… | top users | synonyms

10
votes
7answers
6k views

Loopback to forwarded Public IP address from local network - Hairpin NAT

This is a Canonical Question about Hairpin NAT (Loopback NAT). The generic form of this question is: We have a network with clients, a server, and a NAT Router. There is port forwarding on the ...
2
votes
3answers
798 views

Can I have web server on a home network with 1 public IP address? [closed]

I've got a fairly standard home network with a modem from my ISP, which is connected to a router which then provides NAT to about 3 PCs and laptops. There's a possibility to obtain one public IP from ...
8
votes
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 ...
10
votes
2answers
5k views

How to configure a static wildcard subdomain with dnsmasq

I have a network behind a NAT with a few machines. The machines are: router - NAT, dnsmasq, forwarding - directly connected to the inet server - which runs ssh, www and some other stuff clients - ...
17
votes
7answers
2k views

Why don't more organizations use inside-to-inside NAT or similar solutions to allow NAT hairpins?

Inside-to-inside NAT aka NAT loopback solves hairpin NAT issues when accessing a web server on the external interface of an ASA or similar device from computers on the internal interface. This ...
2
votes
2answers
3k views

Basic iptables NAT port forwarding

I have three machines: A local PC (public IP 1.2.3.4), an Ubuntu 10 Server box in a datacentre (eth0 on 5.6.7.8 public IP), and a third-party server hosting a website outside of my network (let's say ...
2
votes
2answers
360 views

How are connections differentiated from behind NAT routers?

Background: I have a very simple server program written in PHP. It's mostly working, but only as long as there is not more than one client per site. Questions: How does a NAT Router (typical SOHO ...
2
votes
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 ...
2
votes
3answers
4k views

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 ...
9
votes
2answers
861 views

IPv6 without nat but what about an isp change?

I haven't worked with IPv6 outside of 4to6 tunneling on my home pc with stuff like GoGoNet. I've read about how it works in a general way. No NAT required (or suggested) and each client uses a public ...
13
votes
7answers
6k views

Why is it a bad idea to use multiple NAT layers or is it?

The computer network of an organization has a NAT with 192.168/16 IP address range. There is a department with a server that has an IP address 192.168.x.y and this server handles hosts of this ...
3
votes
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 ...
3
votes
3answers
2k views

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 ...
2
votes
3answers
589 views

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 ...
1
vote
1answer
2k views

Cisco ASA 5520 Unable to access external IP on Internal Network

I have an internal network of 192.168.0.x and I have a server nat'd to an external IP address we have. I can't figure out how I need to change my configuration for this thing to get it to work. I'm ...
0
votes
2answers
2k views

Cisco ASA - Configure External Access to a Server

I'm trying to configure my ASA (ASA 8.4(2), ASDM 6.4(5) ) to allow external access to a server (using RDP). I've tried everything, but it doesn't seem to be working. I'm sure it is something simple ...
3
votes
1answer
1k views

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 ...
1
vote
2answers
3k views

AWS VPC + IPtables + NAT: Port Forwarding is not working

Yesterday, I posted a question here but I think was not clear enough in my words. BTW, This question is not a duplicate. I have AWS VPC Setup as below. GOAL/PROBLEM: SSH to Server A from internet. ...
1
vote
1answer
191 views

RRAS multiple different external IPs

I have a Windows 2008 RRAS server with 4 external IP's. Is it possible within RRAS to send outbound traffic through each external IP address once I'm connected to the VPN on that specific IP address? ...
1
vote
5answers
1k views

Multiple Sites on One IIS Server Need Different Outgoing IP Addresses

I have an IIS server set up with multiple web sites, each with their own IP address. It works fine for routing incoming traffic to the right site. However, outgoing traffic all appears to come from ...
0
votes
0answers
256 views

cannot ping through gre tunnel

This question has been merged I have 4 machines machine 1 have ip address 172.13.0.40/24 machine 2 have two ip address 172.13.0.1/24 and 172.12.0.1/24 machine 3 have two ip address ...
0
votes
3answers
179 views

Why i cannot conect to NAT'ed host?

That is a question for simple curiosity: In my LAN i make some hosts available by NAT entry in the DSL router for access from the Internet. That all works fine. What i can never do is using from ...
-1
votes
3answers
740 views

want to Make software router having two nic cards using centos 6.4

I'm new on CentOS. I have a CentOS 6.4 system having 2 NIC cards. I want to setup a gateway so I can get internet from public ip over 1st nic card (eth1) and forward the network over 2nd nic card ...
11
votes
3answers
16k views

Forwarding ports to guests in libvirt / KVM

How can I forward ports on a server running libvirt/KVM to specified ports on VM's, when using NAT? For example, the host has a public IP of 1.2.3.4. I want to forward port 80 to 10.0.0.1 and port 22 ...
14
votes
1answer
27k views

What is the difference between a Source NAT, Destination NAT and Masquerading?

What is the difference between a Source NAT, Destination NAT and Masquerading? For example, I thought IP Masqurading was what they used to call it in Linux? But what confuses me is that in our Astaro ...
8
votes
3answers
9k views

How to configure a custom NAT for use in Amazon VPC

I have an Ubuntu box I wish to use as NAT instance (among other things). I would prefer to avoid using the NAT AMIs provided by Amazon, and instead configuring NAT myself. Currently, my host has a ...
5
votes
3answers
4k views

Unable to connect on natted server from a host computer on the same LAN using public IP address

I have a server statically NAT’d using a registered IP address and it is accessible from the outside. The problem is I cannot access my server from the inside using the registered IP address with a ...
6
votes
2answers
2k views

DMZ subnet: to NAT or not to NAT?

I'm looking at setting up a DMZ behind a Cisco ASA that will contain a large number of HTTP front-end load balancers and SSL offload services - over 100 IPs, concentrated on a smaller number of hosts. ...
8
votes
3answers
11k views

Public static ip for vagrant box

I have server (Debian Squeeze) with 1 ethernet card and 2 public static IPs (188.120.245.4 and 188.120.244.5). What I want: Setup virtual box (Ubuntu) with access via static IP (188.120.244.5). ...
8
votes
1answer
4k views

iptables: Port forwarding with masquerading is not working

I'm having some issues with my port forwards. NAT seems to work ok and one out of the port forwards seem to work (udp port 7887 to machine 192.168.1.100). But not the others. I doubt that it matters, ...
2
votes
1answer
2k views

OS X 10.8: redirecting locally initiated ssh connections to localhost:22

I need to hack the OS X pf to redirect all ssh connections from an user to this machine. I want, when doing $ ssh google.com to get the same results as with $ ssh localhost ie a connection to ...
2
votes
0answers
958 views

Errror on connecting to VPN-server by Demand-dial interface (Windows Server 2008 R2)

I have several LAN-interfaces and internet access over VPN (connect to provider VPN-server). I want to setup NAT from local area networks to internet. For this I install on Windows Server 2008 R2 ...
2
votes
1answer
3k views

Iptables and SNAT

I am a newbie to iptables with NAT. My network setup is as shown below linuxbox2 (192.x.y.a) | (194.160.1.1) | linuxbox1(eth1)-------- Switch ...
3
votes
2answers
228 views

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 ...
3
votes
3answers
606 views

how to connect 2 independent computer networks?

I have 2 independent networks that are connected to internet. Each systems in a network can connect to the internet through the corresponding router/NAT device. i wish to connect these two LANs. I ...
3
votes
1answer
13k views

How are cellphone IP addresses assigned?

When my cellphone accesses a website via the tower and its GPRS gateway, NAT ensures that the sites receive a public IP. Would all phones using a single tower have the same IP? If yes, then how can ...
2
votes
3answers
1k views

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 ...
2
votes
2answers
441 views

Issue NATing server private interface to loopback (for MySQL)

I'm trying to NAT traffic sent to the server's private interface to the loopback (because MySQL bind-address is on 127.0.0.1 and can't be changed but I still need to reach it via the private ...
2
votes
1answer
1k views

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 ...
2
votes
3answers
9k views

PPTP pass through on Cisco ASA 5505 (8.2)

Is it possible to setup PPTP VPN traffic (clients outside and server inside) to passthrough a Cisco ASA 5505 if the outside IP address is also being used for PAT? The Cisco examples forward all NAT ...
1
vote
4answers
7k views

How to properly nest a wireless router behind a wired router? [closed]

I wish to repurpose a wireless router to serve as a wireless access point behind a wired router (serving as gateway to WAN) so that I don't have to buy more hardware and recapture value on prior ...
1
vote
1answer
2k views

ESXi Behind Virtual Machine

Just as a follow-up to my previous question: I have an ESXi server that I'm moving into a colocation facility that supplies me a single IP address. I think I'm going to go the route of setting up a ...
0
votes
1answer
774 views

Is there any way to filter packets (eg. by iptables) after routing is complete?

I want to drop certain packet destined to an ip_address AFTER it has reached the POSTROUTING chain. However, for iptables, the "nat" table cannot be used for filtering so the following doesn't work: ...
0
votes
1answer
464 views

iptables NAT port fowarding and Apache log IPs

Thanks to quanta, I can now use iptables to port forward SSH through to servers behind the firewall using a single IP and multiple ports - original question here. However, if I use this technique to ...
0
votes
1answer
2k views

IOS NAT with multiple interfaces

I am trying to create a DMZ type environment between two internal networks using Cisco NAT. The below configuration is working to permit the two 'nat outside' interfaces to access the dmz 'nat ...
0
votes
1answer
2k views

Multiple interface NAT routing

I have multiple internet connections from different ISPs and I need to route certain traffic over a particular ISP link. I am using Debian for this. The setup is as follows; eth0 (IP address is ...
4
votes
2answers
2k views

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 ...
4
votes
1answer
213 views

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 ...
4
votes
4answers
6k views

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 ...
3
votes
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 ...