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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Route outgoing VPN traffic through local transparent proxy

I have a Digital Ocean droplet (similar to an Amazon EC2 instance) running Ubuntu Server 12.04.3 x64 with both strongswan 5.1.1 (built from source) and squid 3.4.2 (also built from source) installed. ...
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How do I configure DD-WRT to forward IPSec traffic to an internal server to support a road warrior configuration?

I use dd-wrt as my home router setup and that's been working fine. Now I wanted to figure out a way to be able to use my iPad to set up a IPSec tunnel to my home network while I'm on the road. PPTP ...
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How to set up a hotspot with socks5 proxy

I have a laptop with linux installed on it. The laptop has two network interfaces: eth0 and wlan0. Normally I surf the Internet through eth0, and I've successfully set up a hotspot in linux for my ...
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Modify incoming packets before forwarding in Linux

I’m using a Linux (Debian based) system on which IP forwarding is enabled (/proc/sys/net/ipv4/ip_forward is set to 1). I can read the incoming packets using a raw sockets program, but I want to modify ...
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153 views

Block all outgoing traffic for a User running Wine apps

Good day, I'm using a lot of WINE apps under Linux which work just fine, but one thing I am specifically looking for right now is to block their access to the internet (outgoing), with exception of ...
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Iptables error :libipt_cgroup.so doesn't exist while using net_cls.classid in net_cls cgroup subsystem

In kernel document doc/cgroup/net_cls.txt, it introduces the function of net_cls.classid, and show an example of netfilter (iptables) using this tag to perform actions. the command of iptables is: ...
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78 views

Determine if an uplink interface is usable

I have a firewall system that is served by two uplinks to different ISPs. I'm using shorewall to manage the firewall; it load-balances traffic over both interfaces with connection tracking. All that ...
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237 views

Limit bandwidth on HTTP downloads based on file size

Is there a way to limit lets say in iptables or any proxy solution/software if a user is downloading a filesize that is greater than lets say 20MB it will limit his entire download at 2KB/s? ...
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276 views

Centos iptables blocks after reboot

I have a Centos5 installation with kvm on my server. I am using nat portforwarding to ssh my virtual machines. I have several iptables rules and saved then in /etc/sysconfig/iptables. After reboot, I ...
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717 views

How do you add a MAC-based routing whitelist with DD-WRT and the OpenVPN client?

I have an OpenVPN client set up on my DD-WRT home router which maintains a VPN into my workplace. Slight problem: I don't want random lusers who access my wireless AP to have access to my company's ...
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26 views

Nodejs remote debugging ports closed

I have a problem with nodejs remote debugging. I'm using centos on remote server and phpstorm on my PC. When I open putty I type the command: node --debug-brk=5858 main_server.js, and get the ...
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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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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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342 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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148 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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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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150 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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186 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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136 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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144 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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628 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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“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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210 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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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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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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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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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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325 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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489 views

tc/netem and iptables: Delay traffic only from specified ip and port

I have a Ubuntu Router with 2 network interfaces. eth0 is the private network and eth1 is the internet. What I want is the following: All packages (mostly udp) comming from a specified private ip ...
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How to unblock jabber on TI ADSL router with iptables

I have old but reliable Texas Instruments ADSL router. Board AR7RD; BUILD=061005; VERSION=3.7.1 If that matters... One thing that bothers me is that it somehow blocking my jabber (Pidgin ...
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No output returned when curl ing any URL in Red Hat 6 but the same url works in lynx browser

I am trying to install some packages in Python using easy install. But i get a 'Download Error' for any package i try to install. So i tried to test if internet is accessible at all from the machine ...
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262 views

IP forwarding with iptables

Suppose there are hosts A and B. A is allowed SSH access to B based on its IP address. Consider now another host C. C does not have access to B, but if we could route its traffic through A, then C ...
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461 views

iCloud stuff stops working while connected to OpenVPN

I have a fairly simple OpenVPN setup on an OpenVZ VPS with Ubuntu 11.10. Client is the Viscosity client on Mac OS X 10.8.2, and after some testing, we can rule out the client as being part of the ...
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239 views

Load-balancing: response packets not routed - iptables

I have a problem with iptables. I'm trying to setup a load balancer between 2 uplinks. I can mark packets and connections, use ip rule to choose routing table (so changing the gateway). But, when I ...
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468 views

Routing table on Linux not respected

I have a very specific problem, building a Linux VPN endpoint (with external VPN Gateway), which should route certain networks over the tunnel, others via default gateway. The Linux VPN should do a ...
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150 views

Is there a decent diagram of packet flow for a modern era (2.6+) iptables setup?

I'm currently trying to debug a particularly hairy set of DNAT based iptables rules (the UDP reply never makes it back to the original requester) and I'm struggling to visualise the packet flow ...
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How to redirect local connection to my things in IPv6 on linux?

With IPv4 I can make some program connect to my service instead of where it wants using REDIRECT and DNAT targets in OUTPUT chain in iptables (sometimes combined with -m owner) In IPv6 hovewer I ...
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305 views

How to enable iptables with verbose mode in DD-WRT?

I want to log all packets to messages through iptables. Can you help me how to set verbose mode in DD-WRT. Just DYI, I have optware installed to store the large messages file and do log rotation.
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Linux route/IPtables with internal VM network

I am having some trouble figuring this all out. I have Windows 7 [10.10.30.1] ROUTER [eth0=192.168.4.134 eth1=10.10.30.254] Ubuntu [192.168.4.143] I can ping eth0 and eth1 from Win7, and also ...
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Internet Connection Sharing bypassing MAC Filter in Ubuntu Linux

My university gives me an internet connection by Ethernet, DHCP but they have installed MAC Filtering to allow only using my PC. I have a wireless router TL-WR340GD. which has MAC address cloning ...
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Iptables port redirecting. Rule doesn't work or show up in iptabels

I'm trying to redirect some incoming TCP traffic on port 443 to port 999 with iptables in an Ubuntu VM. I am using sudo iptables -t nat -A PREROUTING -p tcp --destination-port 443 -j REDIRECT ...
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585 views

SSH login with secure IP VPN

I have a PC behind a router with port forwarding setup Port 22 for SSH which works perfectly - I can login and everything. What I am trying to do is let this PC connect to a VPN and only allow ...
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Portforwarding to VM doesnt work.. anymore

I have a windows 2k8 server vm on my Ubuntuserver which I use for i.e terraria & apache. It was working great before a little minor accident when the electricity stopped flowing through the cables ...
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How can I restrict my Virtual Machine using an iptables rule?

I am using CentOS Linux and am planning to setup a rule on my VM's iptable. I want to restrict all outgoing and incoming packets to the VM for a temporary period and allow only the DHCP packet to ...
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243 views

Can ipmasq and ufw be used together?

If both ufw and ipmasq manipulate iptables, can I use ipmasq for a quick easy setup and then use ufw afterwards to add security or will the two just trample all over the iptables "stuff"? I'm playing ...