Iptables is a module that provides the Linux operating system functions of firewall, NAT and logging of data traveling over a computer network.

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Preserve NAT mappings across reboot

My Linux router is able to reboot and reconnect all network interfaces pretty fast (~10 seconds, thanks to systemd and a SSD disk), and comes up with the same IP addresses. Unfortunately the reboot ...
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32 views

Trouble with last DROP rule in iptables

Let's say I want four ports to be opened for any incoming packets so I made this ruleset: #> iptables -L -v Chain INPUT (policy ACCEPT 20 packets, 1190 bytes) pkts bytes target prot opt in ...
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63 views

Make application use specific network interface

I have an openvpn connection and I need it to work only for one application, this app uses an specific local port. I used route-nopull on my openvpn config file and then: ip route add default via ...
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24 views

Filtered port with virtual server setup on a NAT

I have a Symphony SY602 ADSL router and I want configure a dynamic DNS to access my system remotely. I made a NAT virtual server in routers configuration and this is what I configured: Server Name ...
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137 views

How to force Google safesearch on entire network

I've a problem filtering web searches on Google domains. Currently I've a linux openVPN Server running with openDNS "family block". I can block a lot of websites with dangerous content and it's ok. ...
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132 views

allow incoming ssh with openvpn client

I have set up an OpenVPN client on my home router. The moment the tunnel goes up, I can no longer ping my router from the internet using its WAN_IP. I would like to allow certain incoming connections ...
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28 views

How can I efficiently filter Dos packets? [duplicate]

I have recently been the victim of some Dos attacks. The facts : I received a very high amount of packets saturating my connection and preventing me from accessing the Internet during one hour ...
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76 views

Site to Site VPN - Openswan and CISCO A2A

Below is the diagram that the VPN connection between Openswan server and CISCO A2A. client A and B are remote hosts with static ips. client X and Y are behind the Cisco firewall. I can see ...
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54 views

Open ports in Ubuntu 13.10 server

Im setting up a realtime gameserver fps-game, and then i need to configure ports. Just to mention, i will setup multiple servers for this game on the same ip address, which means i must open multiple ...
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339 views

Intermittent disconnections when using OpenVPN over SSH tunnel; possible iptables issue?

I've recently set up a Debian Wheezy server with OpenVPN to help out some friends in areas where internet censorship is a problem (including the blocking of VPN traffic in general). To overcome this, ...
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147 views

iptables configuration on Windows Azure (CentOS 6.5) for endpoint load-balanced set

I created 2 VMs (CentOS6.5) on Windows Azure for Postgresql database and HA cluster, everything works fine except when I set iptables service on, the endpoint load-balanced set is down. for security ...
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2answers
83 views

Iptables rules to only whitelist SIP providers

I have an Asterisk box sitting behind an ADSL router/modem. There are no other services on the Asterisk box, just telephony. I am getting a lot of traffic which I think are SIP probes. I've ...
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159 views

Allow internet access to intranet only users using Nginx on Ubuntu

I need to allow some users who only have access to the intranet to access one specific internet site. I'm doing this by using Nginx as a reverse proxy. To test this, I would like to block all internet ...
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553 views

How to forward traffic using iptables rules?

I am new to iptables and I have been doing Google searches for a few days now without finding a good solution to this problem. I have computer A with a public ip address (say 192.0.2.1) that can ...
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40 views

Add IPtables rule by script at the request of another computer

I wonder, is it possible to make an script, which adds rule in iptables by request from other pc? I mean, script "knows" what to do, but addres for rule comes from request. And how do you think it ...
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75 views

Bitbucket SSH and iptables

I'm a newbie in iptables to be honest. I have some basic rules. Everything is blocked by default. iptables -t filter -F iptables -t filter -X iptables -t filter -P INPUT DROP iptables -t filter -P ...
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53 views

Transparently proxifying certain devices on the network

I'm using my computer as wireless access point and router to my home network using hostapd under Ubuntu 14.04. I want to transparently proxify certain wifi devices in the network (identified by their ...
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733 views

iptables blocking all traffic even with ports opened

Simple as I can put it: I can't access my servers with iptables enabled, with default rules. Need to disable iptables to get access. Trying to find the cause. Only difference in setup type is layer3 ...
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149 views

Can't connect to web server from outside my network

I have a Debian-based server that I would like to be able to access from the Internet (no domain name yet, I'm just trying to get it working for now). I already have port forwarding set up on my ...
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185 views

Conntrack/NAT's port mapping for a specific port breaks whenever that port's service is shutdown for too long. How can I fix this?

Linux Gentoo 3.13.6-hardened-r3 #1 SMP Sat Apr 12 09:17:25 EDT 2014 x86_64 Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz GenuineIntel GNU/Linux hardened with grsecurity and selinux with a strict policy in ...
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135 views

Segregating/Separating a device (ATT 3G Microcell) from internal network without using DMZ

I would like to put the ATT 3G Microcell in an isolated network from a network that has the rest of my devices, by which I mean I want the ATT 3G Microcell to only be able to access the Internet, but ...
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143 views

How to stream WiFi cameras over a Linux gateway to my laptop using iptables?

My setup is as follows: Linux gateway has one WLAN configured as WiFi client (192.168.0.100) to a Linksys WiFi AP(192.168.0.1). There are three WiFi cameras connected as WiFi clients (192.168.0.101, ...
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624 views

Synergy client won't connect, despite open port?

I want to use a Debian KDE desktop computer (network name bradbury) as the server, and a Windows 7 laptop (network name Clarke) as the client. I have used this setup before without problems, but then ...
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1answer
93 views

Unable to ping server

I have a Linux server that seems to have lost the ability to respond to a ping.. I recently installed Nagios on another system and need to have this Ubuntu server answer up to a ping.. I'm using ...
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1answer
571 views

What does this iptables rule mean: tcp flags:0x06/0x02 TCPMSS clamp to PMTU?

What does this iptables rule mean: tcp flags:0x06/0x02 TCPMSS clamp to PMTU? Doing iptables -vnL on my DD-WRT router shows the following rule in the FORWARD chain: TCPMSS tcp -- * * 0.0.0.0/0 ...
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519 views

How to create a local-remote-local tunnel to a specific port using ssh

I'm able to establish an ssh connection from my windows computer (localhost - eth1) to my linux computer (remotehost - eth0) by doing: ssh user@192.168.1.100 Instead of using that, because I use ...
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117 views

iptables password protection followup

This is a follow up on my other post about this iptables: plaintext password protection I could not get help in the old topic...I just really need some help... Here is the command I tried, something ...
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1answer
120 views

Use IPTables to force TCP packets over router

To test a TCP-stack program, I need to get the TCP packets via the router. When I try to connect to my server program via the router, the OS does not hit the router as the destination IP is the same ...
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135 views

“iptables -P OUTPUT DROP” blocks DDWRT's web interface

When I do iptables -P OUTPUT DROP it blocks DDWRT's web interface. That is I am not able to access http://192.168.1.1 via Firefox. I put this rules before changing the chain policy to drop: ...
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188 views

using iptables to filter vboxnet (virtualbox host only network)

Im trying to use iptables to filter the traffic coming from a guest OS running on virtualbox. The guest is configured to use a host only adapter for the network, and my Ubuntu host is configured to ...
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209 views

Ping through GRE tunnel discarded between 2 interfaces of a router - Ping does not reach subnet

I have an interesting issue that I hope someone can help with. I am trying to create a GRE tunnel between 2 routers (running Linux Ubuntu 12.04) and pass traffic between 2 subnets trough this tunnel. ...
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203 views

excluding port from VPN client

I use hidemyass which is a vpn service. I use it for privacy reasons. The main purpose of the VPN is for my web browsing. How can I exclude certain ports from using the VPN connection? For example: ...
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1k views

Sharing OpenVPN to specified IP-range on the local LAN

Is it possible and how to share OpenVPN (currently Anonine) -connection to specified IP-addresses on the local LAN? Local LAN consist windows- and linux machines and Android devices. Current setup, ...
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72 views

Define IPTABLES rule

I am working with a linux based UTM appliance and have some disagreement with the client on the operation. THere is a standard GUI to configure port forwards in the firewall but for some reason he ...
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1answer
227 views

Adding a custom SSH port to Ubuntu 12.04 LTS through UFW

I am trying to configure a Ubuntu 12.04 based VPS and I have changed my ssh port from 22 to 803 and everything worked fine. After this I've installed UFW and now I can't login using SSH. Before I ...
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238 views

iptables load balancing for TLS with request routing on the same connection

I am trying to set up iptables rules for TLS connection. I have three internal IP in my machine and I route requests coming on public IP at port 443 to each of these internal IP in RR. -A PREROUTING ...
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129 views

nc connection refused even on loopback

I'm working on an embedded linux system, which appears to be networked correctly and is running ssh (dropbear) and rpcbind. I'm setting up a server application on it, and every single thing I try ...
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1answer
3k views

Redirect incoming https to local ip with iptables

I have a router with 1 network interface (eth0, public ip) and an alias for eth0:0, local ip 192.168.1.1. I want to redirect all incoming https (443) traffic to another server. I tried it with ...
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425 views

Multiple IP addresses through the same interface and iptables

System Admin is not my strong point. My situation is we have 1 website that has 4 domains. The website itself serves different templates/content depending on which domain is used, simulating 4 ...
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142 views

NAT routing command in windows

Is there any specific command in windows which do the following task: I want to modify the source IP address in the packet whose Destination IP is not in the private LAN, i.e., I have a virtual ...
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271 views

I need some help proof reading my IPtables rules, my rules seem to work but I cannot be sure

Like the title says, I need some help proof reading my iptable rules, my rules seem to work but I cannot be sure. My set up is as follows: ISP ---> cable modem ---> Ethernet switch ---> ...
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243 views

NAT router sends RST to a server where a NAT'ed client is connected to

As I tried to remove some Ethernet wires in my home network, I took an older notebook with Linux and tried to use it as some kind of Ethernet-2-WiFi-NAT-router (Wi-Fi card can't act as bridge, so I ...
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84 views

Lubuntu UFW does not respond

I have been using ubuntu for a long time. Nowadays, I wanted explore lubuntu. However, I cannot configure ufw. Actually I can but it does not respond. Basically, I cannot get the result of "ufw ...
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141 views

Change UDP port with iptables for VPN clients

What I want to do is say that for all UDP connections on interface ppp0 that have a destination port of 53, change that destination port to 1053. I am attempting to change the destination port of UDP ...
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1answer
1k views

Limit UDP outbound traffic to loopback (localhost) instead of eth0

Atm i'm testing it on Ubuntu Server at VMware Workstation + Windows 7 local host with bridged connection. Later this has to go to live server. I have VLC streaming video file on Ubuntu with cvlc ...
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812 views

Iptables configuration to allow Steam Client

I recently got and setup a small linux (Debian) router box. I'm adding it to an existing network to create a small subnet with specific properties, namely internet content filtering. I'm highjacking ...
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3answers
673 views

linux routing outbound port 80 traffic via ssh tunnel, iptables, or a simple route

I have two hosts, A and B. Host A hosts services on port 8080 and has outbound internet firewall rules allowing port 80 and 443 access to Host C. Host B is on the same subnet as Host A. Host B is ...
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324 views

Advanced QoS on prioritized first packages set by ISP

I have the following problem my ISP (Fibertel from Argentina) accelerates, 'enhances' the first 6.8 megabytes of downstream transfer and it's seems the first 1.8 megabytes of upstream transfer. This ...
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133 views

iptables simple forwarding setup woes

I have iptables running on a host (acting as a firewall) in a Linux namespace with only one network interface: h2-eth1 (has an IP and MAC address) I have set up my switch to forward all packets to ...
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783 views

Port-Forwarding for Click'n'Load remote usage

I've got JDownloader running on my HTPC and access it via VNC. The problem with Click'n'Load (CNL) is, JD only listens on localhost:9666 for incoming traffic, and the browser applications only send ...