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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FortiGate 310B public ip pool into internal port

I have a FortiGate 310B with WAN port with /27 public IP pool from the ISP. The WAN port is configured with primary IP 1.1.1.1/27 I would like to provide servers within the Internal port a public IP. ...
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376 views

Cisco ASA firewall blocking requests to internally hosted DNS server

I have a DNS server behind a Cisco ASA firewall. The Cisco firewall is performing NAT. When inside the network, I can NSLOOKUP directly to the server. When the client is external, requests time out. ...
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435 views

Reaching Local Network which is under NAT with no public IP

I have a place called (lets say) REMOTE. REMOTE is connected to the Internet using 3G/4G Modem + Router. Unfortunately my mobile Internet provider does not give me public IP address. In REMOTE I have ...
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1answer
347 views

Cisco IOS - Problems with NAT and port forwarding

I have a problem forwarding ports. I have configured a NAT pool of 1 address (192.168.5.2) and assigned that address to the WAN interface. I assigned networks to the access-list, and bind the two ...
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1answer
499 views

Forwarding a port on the loopback interface to a remote IP/port

I have two Docker containers that I'm trying to network together in a specific way. Container A is running a Redis server on port 6379. Container B is running an interactive shell and needs to access ...
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1answer
1k views

AWS public subnet autoscaling group with outbound NAT

I have seen this question : Static IP address for outgoing traffic from AWS autoscaling group but it doesnt seem to fit exactly what im trying to do. Here's the scenario: I have a autoscaling ...
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2answers
722 views

iptables drops packets after POSTROUTING

I have a malware analysis environment that will intercept traffic to arbitrary domains and Internet services using InetSim. I have a sandbox that has its DNS server set to the InetSim instance, and ...
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2answers
48 views

Trying to use source routing on two different interfaces

I have defined the following rules: -A POSTROUTING -j SNAT --to-source [publicip] -A POSTROUTING -j SNAT -d 192.168.0.0/24 --to-source 192.168.0.6 Basically, I want only the private network to go ...
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5answers
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Router limits network performance but its CPU load isn't 100%

I'm using a PC Engines APU device running FreeBSD as a NAT router. The setup is very usual: one WAN connection and one LAN connection. Theoretically, WAN connection is 800/40 Mbit/s and the LAN one ...
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3answers
243 views

Cisco ASA NAT - internal host see its public ip

I have a server hosted by a provider which uses Cisco ASA to do nat. The problem I have is that the internal server that is nat-ed with a public ip will see its public ip as source ip. This basically ...
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207 views

Chaining two containers with docker

I have two containers that I have chained them together, so traffic that comes to container 2, first passes by container 1. I set container 2 --net=none. Host --- Container 1 --- Container 2 this is ...
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2answers
1k views

NAT a single IP using 2nd WAN Internet

I have a mikrotik RB750 (6.22) acting as a gateway for my LAN. Here is the basic configuration: Ether1-WAN1 (1.1.1.10/24) IPs are hidden for privacy Ether2-WAN2 (2.2.2.20/24) Ether5-LAN (192.168.1.1/...
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732 views

Why can't I SSH to this AWS NAT instance in a public subnet?

For experimentation purposes, I’m trying to setup an AWS EC2 inside a VPC that has both public and private subnets as described in this tutorial. However, when I try to SSH in step #2, it fails (...
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1answer
36 views

How to find how a port has been forwarded from main server to hypver v vm

I must appologise for being a novice in server administration but I have somehow been given the responsibility and I have spent a long time reading up on this. The issue I have is that the previous ...
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1answer
547 views

Use Openswan / IPSec on Ubuntu server to connect to existing Openswan VPN - NAT broken

I have an existing Openswan VPN, all working fairly well with Windows, Mac and Phones. [Office 192.168.0.0/24]---[VPN A.B.C.D]----[Internet]---[Home Routers (NAT), Dynamic IPs]----[Workstations] Now ...
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1answer
78 views

iptables port forwarding from public ip but not from 127.0.0.1

i have an issue with my network setting and i need a port forwarding a bit advanced. I need : - All packets that arrive on my public_ip on port 54321 to be forward on port 12345 but i don't want any ...
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1answer
975 views

Asterisk behind NAT sets wrong Contact Header

I'm using SIP with asterisk 13.1.0 behind a statically configured NAT. The servers private_ip differs from the public_ip, where I can reach it. I've already set these options in the sip.conf file. ...
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2answers
83 views

Port forward for SSH works to one system but not another

I have two systems sitting on a NATed network. When I forward port 22 to system A, I am able to connect directly. When I forward port 22 to system B, I am not able to connect. I am, however, able to ...
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1answer
35 views

IP forwading amazon ec2 another server IP

I use this command in windows azure (NAT), to redirect all requests to another server with other IP iptables -t nat -A PREROUTING -i eth0 -d 10.240.154.15 -j DNAT --to-destination 192.188.47.63 ¿ ...
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1answer
836 views

How to forward ports to DMZ using iptables and separate modem

I have a network that looks like this: ADSL VLAN 2 VLAN 3 ------[Modem]----------[firewall]----------[intranet PC] | | ...
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1answer
259 views

Linux firewall, ADSL bonding, two default routes

I am trying to set up a Linux firewall (ubuntu 14.04) to use two bonded ADSL lines for load balancing purposes. I found by searching the forum link to this: http://lartc.org/howto/lartc.rpdb.multiple-...
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1answer
61 views

Is there any solution to change the source IP from outgoing WAN A to receiving WAN B?

I am configuring a office router for crossing the GFW in China. I want to use WAN A(actually a low bandwidth VPN tunnel) only to send package to target servers (YouTube for example). And change the ...
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1answer
2k views

How to make connections answer from the same gateway they entered in RouterOS?

I have a MikroTik RouterOS 6.23 device, and my network is as follows: Router | |-- bridge1_LAN (wlan1 + ether1) (192.168.0.210) -- LAN (192.168.0.0/24) | Here is where computers are. Those ...
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170 views

iptables: static ephemeral port maps

I have a VPN on my Linux server which does IPv4 NAT, example: iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT iptables -t nat -A ...
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1answer
8k views

NAT doesnt work on CentOS 7(Firewalld)

I have configured nat to make my CentOS 7 into a router. I have used firewalld to do this. But unfortunately it doesnt work. I have no idea which causes the issue. I tried the same configuration in ...
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1answer
548 views

Possible for Socket communication between 2 internet-connected GSM modems?

I have 2 internet-connected 4G modems connected to 2 separate computers and I'd like to send/receive data between them with sockets (UDP) using the modems' packet-switched 4G Internet connection, not ...
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1answer
2k views

NAT Rule changes from ASA software 8.0 to 8.4

I have an Access Rule and a NAT rule that works fine with on the Security Appliance Software Version 8.0 The rule is as follows: However, I am having trouble making the same rule work on an ASA ...
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1k views

Set up pfSense on AWS VPC?

I am attempting to setup pfSense as a nat box for internal servers on a VPC. I have followed the guides posted for configuring access and have followed the AWS instructions for setting up and ...
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2answers
3k views

NAT to two different servers on the same port via hostname with Mikrotik RB2011

I have a Mikrotik RB2011 router, running RouterOS which connects to the internet via a static IP. In my lan I have two different servers, one that is on IP 192.168.89.11 and another on 192.168.89.12 ...
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321 views

Amazon VPC NAT performance problems

I have a set of servers inside an Amazon VPC, whose job is to get image files from S3 and process them. The S3 downloads would frequently stall, sometimes for over 2 minutes, but all would eventually ...
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321 views

OpenVPN server cannot ping client (routing/iptables issue?)

I am not sure exactly where the issue is here. I'm fairly sure that this is some NAT or iptables issue on the OpenVPN server but am lacking the networking know-how to fix the issue. The crux of the ...
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1answer
106 views

Expose a machine on the far side of a VPN

We're using a VPN to connect a remote office to our main office, and a machine in the remote office needs to expose port 22 to the outside internet. Complications: The main office has a fixed IP ...
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0answers
174 views

Blindly bridging wireless client with MAC NAT

This is the usual "I want to bridge wifi with ethernet" question, but I need something specific here. My Linux box has a wlan0 interface which is in station mode, with MAC aa:aa:aa:aa:aa:aa, and a ...
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1answer
77 views

getting to server on internal network with the external address

I have a network behind a nat with exchange server. Mobile device are configured to access exchange using its real address (the single ip that the entire office hides behind) When the mobile device ...
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1answer
72 views

Why Use a NAT Instance? [closed]

Consider the following VPC: Public subnet with app servers and a separate NAT instance. Private subnet with database server. What benefits do we gain by using a stand alone NAT? EDIT: Why use ...
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1answer
861 views

Apache presents wrong certificate when accessed via load balancer [duplicate]

I've got a server that has two SSL certificates set up, one for internal access where it is accessed along the lines of host.my-local.net and other for external access where it is accessed similar to ...
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2answers
48 views

Could I have 2 nat on vpc [closed]

There is a vpc on amazon that has two subnets. The outer one has internet access and the inner one using NAT server to connect to internet. Inner subnet have plenty of servers for development and ...
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3answers
2k views

Internet access from private VPC subnet?

My brain is a little bit fried trying to figure this out but I can't seem to get private subnets to connect to the internet to grab updates for example. Basically all I want is web access for these ...
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3answers
454 views

Forward Traffic in & out, NAT iptables

I have a box setup as DHCP Server with NAT ipv4 forwarding enabled. Currently the box uses eth0 to connect to a local network and has access to the internet, it has another 3 interfaces, eth1, eth2 ...
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2answers
262 views

Cisco static NAT not working on LAN side

I have a web server in my private network that has the ip address 192.168.1.134. I need to allow users to access this web server from both the internet and the private network. The public ip address ...
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2answers
6k views

OpenWRT Barrier Breaker - Router does not route

I've upgraded my TP-Link 1043 router to OpenWrt 14.07. Everything is perfect, Wifi and LAN are bridged, LAN machines can access each other by name, I can SSH into the router, and the router can access ...
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1answer
287 views

Force Cisco ASA to change source port NAT

I have a 2 devices, a Cisco ASA and sitting behind it another device. Both the Cisco and the other device have IPsec tunnels but to different locations. I need to ensure that the source port of the ...
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3answers
2k 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 ...
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2answers
334 views

How to redirect a packet with iptables that match a certain pattern? (eg a QUERY command with UDP)

I have a certain packet that I want at all times to be redirected to a specific ip on my virtual network interface. As for now my iptables is setup like this: (the commands, I use \ as for now to ...
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1answer
125 views

How to route an IP Whitelist to one VM and all other to a second VM on proxmox?

Is it possible on linux to have a whitelist of IP's that are allowed to reach a specific VM on the internal NAT? eg (public ip (proxmox) --> My VM for whitelisted IP's (192.168.0.1)), and if the ...
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2answers
3k views

Make CentOS 7.x a port forwarding NAT device

I would like to make CentOS a port forwarding NAT machine using iptables. This is the first time I've tried this and I think i might need a little help. This is the configuration i'm trying to ...
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1answer
195 views

Are iptables prerouting (DNAT) packet changes visible to subsequent chains?

I was reading Rusty Russell's NAT Howto when I came across this section: 6.2. Destination NAT This is done in the PREROUTING chain, just as the packet comes in; this means that anything else on ...
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1answer
2k views

My iptable rules do not allow VPN connections

I have installed OpenVPN on my Archlinux server and modified my iptable rules to allow incoming traffic on port 1194 and forward it to the tun0 interface. When I disable/stop the iptables, the OpenVPN ...
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1answer
646 views

AWS EC2 Ubuntu 14.04 Instance smtp port forwarding from 25 to 2025

I am trying to step up port forwarding from port 25 to port 2025 on the same AWS EC2 Ubuntu 14.04 instance using iptables. I am using port 2025 to receive income emails using Alfresco. The first step ...
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2answers
650 views

Static public IP issue on Cisco ASA 5512x

This is our scenario: We have an Cisco ASA 5512x and we have 2 different Internet connections from different ISPs connected with it. ISP A is being used for the users browsing traffic(normal internet)...