Questions tagged [nat]

Network Address Translation, a technology used to translate a private IP address into a public IP.

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101 votes
9 answers
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How to do networking between virtual machines in VirtualBox?

I have two virtual machines in VirtualBox. I would like to do networking between them. For the moment I have the default configuration on both, but they seem to have the same IP-address 10.0.2.15. I ...
Jonas's user avatar
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45 votes
5 answers
53k views

SSH access to office host behind NAT router

I would like to access the ssh port of my office linux host from home. Unfortunately the host is located behind a NAT router. So, the IP address is not publicly available. There is however access to ...
ritter's user avatar
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45 votes
2 answers
51k views

How does a NAT server forward ping ICMP echo reply packets to users?

NAT uses an IP address port number combination to hash the outgoing requests. Since ping requests consist of ICMP echo request packets, they do not have any associated port number. How does a NAT ...
Rohit Banga's user avatar
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39 votes
21 answers
277k views

No internet connection in Virtual Machine on selecting NAT in VMWare workstation

I'm facing this strange problem from yesterday where if I select NAT as the network adapter in VMWare, I'm not getting any internet connection in the VM. I have a requirement where I have to have the ...
Amogh Natu's user avatar
39 votes
6 answers
6k views

Safely adding insecure devices to my home network

I have a few Internet-connected devices which I don't trust to be secure, but that I would like to use anyway (a smart TV and some off-the-shelf home automation devices). I don't want them on the same ...
Chris B's user avatar
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36 votes
4 answers
205k views

How will a router with NAT disabled behave?

I noticed that my home router has the option to disable NAT. How will the router behave with NAT turned off? Will it simply broadcast all incoming traffic to the subnet?
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35 votes
4 answers
202k views

Does mailx send mail using an SMTP relay or does it directly connect to the target SMTP server?

Suppose i send a mail using the following the following command: mailx [email protected] then does mailx first try to find out the SMTP server of my ISP for relaying the mail or does it connect directly. ...
Rohit Banga's user avatar
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30 votes
9 answers
69k views

Is it possible to host a web server from behind a NAT

My PC is behind a NAT router that has a public IP address. If I want to host a website then I believe I need a domain name which I can purchase from some site which would pledge to resolve all DNS ...
Rohit Banga's user avatar
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29 votes
5 answers
88k views

How is double NAT bad practically?

As the ISP-provided modem was generating pretty weak WiFi signal I've disabled its WiFi function, bought an Apple AirPort Extreme and connected it's WAN port to the modem. Now everything works just ...
Ivan's user avatar
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25 votes
5 answers
86k views

Set up a web server behind a Carrier Grade NAT

I was trying to set up a small home server. I use dynamic IP adress. My router's wan adress is like this 100.70.81.xxx and my public ip is 81.213.177.xx I made port forwarding in my router. www, ...
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25 votes
1 answer
85k views

NAT vs. port forwarding [duplicate]

Possible Duplicate: What is port forwarding and what is it used for? What is the difference between NAT and port forwarding? Are they two different names for the same thing? What would be a short ...
Bunkai.Satori's user avatar
23 votes
6 answers
13k views

Is it possible to see my external IP address without making an outbound web request?

If your connection is NAT'ed, is it possible to see your external IP address without making an outbound web request? Any OS (Windows, Linux, etc.) is fine.
Axel Persinger's user avatar
22 votes
3 answers
16k views

NAT and UDP replies

Sanity check please. If I send UDP packets from Machine A behind a NAT to Machine B's port N, where Machine B is outside the NAT (elsewhere on the Internet), can I reasonably expect that NAT to pass ...
tomfanning's user avatar
21 votes
5 answers
75k views

HOST can't connect to GUEST with NAT networking at Virtualbox but others

It confuses me about NAT networking, but I can use VMware and Parallels Desktop to do that. I knew NAT how it works, just need an explain about this situation. The following is from official ...
TonyY's user avatar
  • 311
21 votes
2 answers
62k views

Port Forwarding from inner network to inner network (hairpin NAT)

I've successfully setup a port forwarding on a Mikrotik router that translates every request going to WAN ip address on port 8844 (let's say: 20.20.20.22:8844) of mikrotik to the local ip address and ...
Joudicek Jouda's user avatar
20 votes
2 answers
8k views

How will home networks work in the IPv6 world?

Right now, I have a home network setup behind a Netgear router. That router has a public IP address I get from Comcast. I also have a computer setup on my home network running Linux that runs a DHCP ...
Mike Christensen's user avatar
19 votes
8 answers
51k views

ssh through a router without port forwarding

I have a linux server, and I want to put it in a home network behind a router. I need to ssh to this server sometime from outside, but I don't want to set up port forwarding because I don't have ...
Jiechao Li's user avatar
19 votes
2 answers
23k views

How does the router know which device to send packets to? [duplicate]

my question does not concern how it moves through the internet, but how it moves through the router to a certain device. All devices connected to a router in a home network have the same external IP. ...
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18 votes
3 answers
35k views

Virtualbox -> Can't add 2nd adapter to network for VM

I have a Debian Wheezy VM running in virtual box with the 1st adapter being NAT. However I want to also add a Host-only network but I can't add 2nd adapter to network for VM, it is grayed out. Any ...
Nikos's user avatar
  • 630
18 votes
2 answers
65k views

Windows 10 - NAT - Port forwarding & IP masquerade

I'm looking for a way to get iptables functionality in windows 10. I enabled IP routing and I need to forward tcp data to another host (port 8080) and then forward his response while masquerading IP. ...
Orestis P.'s user avatar
17 votes
5 answers
8k views

Does NAT provide security?

I'm following discussions about the IPv4->IPv6 transition, and IPv6 doesn't seem to like NAT at all. I've always thought that NAT was helpful in v4 for some security, I know it doesn't really hide ...
Neth's user avatar
  • 565
16 votes
4 answers
10k views

Is my router's IP address really public?

I have a common home network consisting of a wireless router with many devices connected to it. I understand that because of NAT, all devices attached to the router connect to the outside of it via ...
MPA95's user avatar
  • 271
15 votes
8 answers
114k views

How to get my external IP address (over NAT) from the Windows command-line? [duplicate]

The Windows "ipconfig" command can only show me the parameters from the Ethernet interfaces from my machine (even with the ipconfig /all argument). It can show detailed information about the interface,...
Diogo's user avatar
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15 votes
1 answer
21k views

How would I test to see if I'm behind carrier grade or regular NAT?

Inspired by the comments to this answer and its question. Some of my local ISPs are using carrier grade nat, and as someone who occasionally runs his own servers, remote support, it would be highly ...
Journeyman Geek's user avatar
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14 votes
6 answers
14k views

What's the difference between DHCP and NAT? Are they mutually exclusive?

I know this is a rather basic question, but I'm struggling to find sources online to clarify it. As I understand it, in NAT, the router which connects the private network to the public internet has ...
S. Dauncey's user avatar
14 votes
2 answers
5k views

How does the airconditioner app on my phone access my aircon controller through my router?

I understand how a router uses NAT/NAPT to enable a client on my home network to request a packet from an external server, and hence how the router knows to which client to send the packet that is ...
steerage250's user avatar
14 votes
3 answers
32k views

UPnP port mapping client for Linux

Is there any client that can request mapping and unmapping ports via UPnP port mapping behind a NAT gateway? I had problem with PortMap. I want this mostly for testing purposes.
Atilla Filiz's user avatar
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13 votes
3 answers
123k views

How to access server running in VirtualBox from the host?

I am running a web app on the VM. I can see the app at localhost:8888 via a browser from within the VM. I cannot see the app from the host at the same URL. That is the goal. I tried VBoxManage ...
Kirkland's user avatar
  • 233
13 votes
1 answer
12k views

Linux iptables NAT of an entire /24 subnetwork

My purpose is to NAT (translate) all IP addresses that reach eth0 on all ports and protocols this way: 192.168.55.x -> 192.168.42.x (I have ip forwarding enabled and 192.168.42.0/24 subnetwork is on ...
Djee's user avatar
  • 243
13 votes
2 answers
20k views

how to access samba on a guest Linux behind the VirtualBox NAT?

On my laptop, I'm running Ubuntu 9.10 under WinXP using VirtualBox 3.1.2. I want a setup where: The guest can freely access the internet. The host can access the guest files via Samba. The setup ...
noamtm's user avatar
  • 367
12 votes
4 answers
9k views

SSH connection between two behind-nat computers through third public-ip computer

I have a computer at home (home-server) that runs irssi, rtorrent etc. My ISP is blocking every traffic from outside (dumb, I know, but it's the only ISP I can have). I want to be able to log in into ...
seler's user avatar
  • 353
11 votes
2 answers
25k views

How to use NAT iptables rules for hostapd

My PC is equipped with two net interfaces, wlan0 & eth0, and I want to use WiFi port as an access point on wlan0. I used hostapd facility and it works properly in routing mode within the local ...
mackowiakp's user avatar
10 votes
9 answers
20k views

VMware Player loses internet connectivity

Periodically, the internet simply stops working in my virtual machine, and the only way I can get it working again is to restart the host computer. Since I use the virtual machine specifically for ...
Martha's user avatar
  • 930
9 votes
6 answers
14k views

how to ssh two computers behind NAT and Firewall, without third computer

I am trying to ssh into my Linux box at home. My home is a dorm-style environment - NAT and Firewall with personal laptop running Arch Linux. My work is corporate style Windows 7 - NAT and proxy ...
user1026169's user avatar
9 votes
1 answer
33k views

Why disable NAT passthrough?

According to this article NAT passthrough is a router feature enabling outbound VPN connections from LAN computers. My Asus router has NAT passthrough for three VPN protocols: PPTP, L2TP and IPSec. Of ...
jacwah's user avatar
  • 195
8 votes
7 answers
34k views

How can I make my home PC a web server?

I am running Apache Tomcat on my PC. My PC is connected to a router in my house and the router is connected to my ISP. Now I want to run a server on my PC so that my friend can view my site hosted on ...
user avatar
8 votes
4 answers
17k views

What is the difference between NAT and SNAT\DNAT?

Following the question in subject, I guess there is a slight difference between NAT and the others. Is it that NAT translates a complete private network, as SNAT\DNAT translate per package? Thanks.
dushkin's user avatar
  • 291
8 votes
5 answers
12k views

How to ssh into home LAN behind ISP NAT (no public IP address)?

My property management company provides free internet access. All the apartments in many buildings are behind some common NAT, so none of us have our own public IP addresses. Thus, services like ...
Matt J's user avatar
  • 183
8 votes
2 answers
957 views

What do the various IP addresses mean?

When I visit a website (e.g. whatismyip.com) it states that my IP address is 13.151.xxx.xxx. However, when I run ipconfig, my IP address is 192.168.0.xx for IPv4 and my DNS adress is 202.xx.xxx.xx. ...
KMC's user avatar
  • 1,969
8 votes
4 answers
47k views

Is it possible to get the NAT Ip Address?

is it possible to get my nat ip address across the Internet? I know I can see my ISP address but not my internal address. I remember seeing this done one time but I am thinking it was a java applet ...
johnny's user avatar
  • 2,003
8 votes
1 answer
9k views

Hairpinning in Linux

I have a router in which I installed a Linux system. I want my router to support NAT hairpinning. Does a such feature exists in Kernel Linux? If yes how to activate it? Are there a patch to apply it ...
Mohamed KALLEL's user avatar
7 votes
4 answers
18k views

Why do we have NAT if we could just assign a public IP address?

If the private address block is simply used to allow the router to determine where packets can and cannot be forwarded from (because private addresses need to be unique on their own network, but can ...
Paul Wiklund's user avatar
7 votes
2 answers
15k views

Mikrotik NAT halves WAN speed

I have a 951G-2HnD as a router. All connections are via ethernet cables. I observe the following: When I connect to the ISP via router, speed is about 270 Mbit/s, while ISP claims my plan has 500 ...
Uprooted's user avatar
  • 187
7 votes
3 answers
17k views

Connecting to VirtualBox guest (ubuntu) from host (osx) via NAT?

I have a VirtualBox guest (running Ubuntu) configured with NAT through my host laptop (running OSX). It was my understanding that with NAT configured, I could access the guest from the host (w/o any ...
EvanK's user avatar
  • 313
7 votes
2 answers
14k views

Linux Netfilter: How does connection tracking track connections changed by NAT?

At the moment I am diving into the details of the Netfilter Architecture of Linux. I am already familiar with Netfilter hooks, tables, chains, the different kernel modules, etc. But there is one ...
idlmn89's user avatar
  • 213
7 votes
1 answer
2k views

How does a mobile phone carrier, who uses CGNAT, know when you’re using the internet?

How would a phone carrier know when you’re using the internet when they use CGNAT as other users would have the same IP at the same time? How would they be able to distinguish who’s who and how would ...
Chardonnay1234's user avatar
7 votes
3 answers
16k views

Bridged vs. NAT: a Virtualbox and VMWare Comparison

I installed VMWare Workstation 7.1.x and Virtualbox 4.0.8 on two different hosts, so I could compare. I set the virtual network adapter on both to NAT, which was successful for both. The result: ...
Brent Arias's user avatar
7 votes
2 answers
3k views

VirtualBox dhcp server is leasing the same IP to all guest VM's connected to a VirtualBox Nat Network

I created a new nat network with dhcp enable through GUI on my VirtualBox 6.0 and connected 2 Guest VM's to it but keeps assigning the same IP to both VM's even if they are running at the same time. ...
Daniel Chiang's user avatar
7 votes
1 answer
8k views

How does Bittorrent work in peers behind Carrier-grade NATs

When I google "whats my IP" it says, something like "112.134.x.y". But when I go to the router configurations and under WAN IP it says "100.68.a.b"(As far as I know it's a routable IP). So, I must be ...
Lazzy's user avatar
  • 73
7 votes
2 answers
12k views

Changing the default network VirtualBox assigns to VMs attached to NAT

By default, VirtualBox assigns a 10.0.2.0/24 address to a VM attached to NAT. Is it possible to change NAT to a different network? This is not a duplicate question. I know it is possible to define a ...
Ben's user avatar
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