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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Fedora / Vagrant Firewall Issue: Unable to Connect to HTTPd / MySQLd / Webmin

Yesterday, I migrated from Ubuntu to Fedora 20, and after some fiddling with NFS and iptables I was able to get my vagrant instance (CentOS 6.5) to boot, mount the NFS share, and was able to access ...
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162 views

How to share ppp0 to wlan0 with redsocks

I can't understand the meaning of this: I have a USB modem along with a USB Wifi router, and I use redsocks for ppp0. Then I want to forward the incoming connection from Wifi to redsocks. I have ...
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102 views

How to check/adjust SSH server on embedded board

I'm currently having difficulties connecting to an embedded board from my Linux machine through ssh. The embedded board is a FOX G20 V with a Linux OS. I've tried to connect to the board through ...
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3answers
1k views

bridge does not forwarding packets centos

I am using CentOS 6.5 64 and use xen to create a virtual machine (CentOS) ifconfig [root@CentOS ~]# ifconfig eth0 Link encap:Ethernet HWaddr 08:00:27:54:B3:FA inet6 addr: ...
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246 views

Why does iptables suddenly stop properly forwarding packets?

My home network consists of a desktop PC running Slackware 64 [192.168.1.10]. My Windows PC [192.168.1.20] is routed through the Slackware PC via a direct ethernet connection. In addition to iptables, ...
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181 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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516 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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66 views

Iptables on mini-Linux, hosting VMware Player with Windows, blocking access to www

we have a special kind of system at the university. A mini-Linux (Ubuntu 13.x) is loaded via PXE, afterwards the VMWare Player on this Linux is starting a selected VM. The connection setting of the ...
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55 views

Ports in Linux vs Windows

I'm studying for a security class. I know that ports in Linux are tied to a process. So if I wanted to close/shutdown a port, I'd end the process that's using it. So if I'm in Windows, what's ...
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157 views

Redirecting internal traffic to gateway's port-forwarded external endpoints directly to intranet destination

There's an intranet and CentOS-powered gateway that provides connectivity for intranet devices. Typical port-forwarding in gateway's iptables ruleset looks like this (TCP version is provided): ...
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731 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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148 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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1answer
73 views

How to specify a certain device to access the Internet via the OpenVPN client of router?

Involved Devices: a VPS, a router, and several devices that connected to the router. Final Aim: Base on the OpenVPN client which has connected to the server on the VPS, specify only one local device ...
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1answer
284 views

How can I detect long-lived connections and mark them for shaping

I would like to detect TCP connections which have been open for more than one minute (or for greater than N bytes, or M packets), so I can classify them as bulk traffic ("downloads") and de-prioritise ...
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3answers
5k views

Source Based Policy Routing & NAT (DNAT/SNAT) aka Multi WANs on CentOS 5

Originally posted at Unix and Linux but nobody was able to answer it, so m migrating the question here: My question is regarding Source Based Policy Routing on CentOS 5 with 2 WANs plus a LAN (NAT) ...
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1answer
974 views

Route internet traffic from openvpn tun0 to eth0

I can't figure it out. How do I give chosen VPN-users access to internet trough eth0? All server traffic goes trough eth1. The eth0 is only supposed to give VPN-users internet access on chosen ports ...
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2answers
839 views

Apache runs locally but can't be accessed from other machine

I'm running Apache 2.2.3 in a VM for a test environment on CentOS 5. Apache is running and responding to requests on the VM itself. If I run "lynx localhost" on the VM I do get my test page. When I ...
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635 views

configure iptables to block all(as much as possible) bittorrent traffic

good day all This is my current iptables setup Generated by iptables-save v1.4.7 on Wed Apr 9 13:50:31 2014 *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] :LOGDROP - ...
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171 views

IPtables preventing outgoing packets

I am trying to setup firewall rules on a RHEL webserver, so that my webserver can serve up web pages and at the same time download remote files using curl/wget. Problem I am experiencing is I can only ...
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97 views

Display port numbers and port names

How do I display both port numbers and port names at the same time? I can display the forward port numbers (i.e. 22, 25, 1000, 443, 80) using the following: [root@michaels ~]# iptables -L -n Chain ...
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650 views

Routing internal traffic in centos to the internet using iptables

Hello friends i am struck in routing traffic from the office to internet i have a network structure like this http://asthana.me/images/ip.png I have assigned static ip to the cent os server(which ...
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72 views

Turning iptables off on development server permanently?

What would be the downsides of turning off iptables permanently on a development environment? I don't like the fact that every time I restart virtual box I must do: service iptables stop service ...
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181 views

Bind incoming packets to 1 interface and outgoing packets to 2nd interface?

I am have a Linux machine with 2 network interface cards, I need to use one for incoming packets, other for outgoing packets.
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How to route the incoming connections through a specific interface?

I have multiple ethernet cards with two different set of networks configured on them. The output of route -n is given here:: Kernel IP routing table Destination Gateway Genmask ...
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136 views

How to allow squid to grant access for outlook

I have configured squid at RedHat Linux 5.4 and all my Windows networks use 192.168.5.100 and port 3128 as proxy for accessing Internet. But while sending and receiving emails at Microsoft outlook ...
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559 views

Chromecast and accessing Netflix from outside the US

I have given this as an answer, but there is a question involved so that's why I'll post this again. You can find the answer here: http://superuser.com/a/734838/311358 I have a computer (iMac) that ...
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1answer
460 views

Chromecast, Unblock-Us and Edimax BR-6478AC router

It seems that Google has hard coded the Google DNS into the Chromecast, thus making it pretty much useless for anyone outside the U.S. who wants to use it for Netflix and Hulu. I have the above ...
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1answer
109 views

Connected to vpn but can't connect to internet

I am using ubuntu 12.10 as a vps. And I am trying to configure a vps server on it. I can connect to the vpn but just can't get internet access. Maybe because I don't know how to write a iptables. ...
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103 views

packages from router dont match iptables dnat rule

I have the follow rules to forward port 443 from external to a internal host: IF_INET=ppp0 IF_INET_IP=1.2.3.4 # Router External IP IF_LAN_IP=192.168.0.1 # Router Internal IP ...
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22 views

Blocking an outbound port for a bridge'd nat'd inteface

eth0 and wlan0 are bridged to br0, and have access to the outside world through eth1 and NAT. I'd like to block an outbound port on wlan0, but leave it open for eth0.
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141 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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2k views

Howto compile a kernel module on CentOS [required packages]

What yum commands do I need to get available packages installed on CentOS to build a iptables MATCH kernel module.
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60 views

Can't SSH into a computer that is connected to a VPN

I set up a linux machine with an ssh server that I can connect to from an external network. When I have the server computer use a private VPN though, I can't ssh into it remotely anymore. Is there ...
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58 views

Setting/clearing packet's TCP flags with iptables

I know iptables can match packets with certain TCP flags using --tcp-flags. But how do I set or clear some flags on a matched IPv4 packet?
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616 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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207 views

Editing IPTABLES nat rule in cron job

I am sitting here with an issue: I need to switch the source interface for iptables' NAT rule at a given time. I want to basically do soemthing like this - caution: concept code: #!/bin/bash if [ it ...
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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
546 views

How to transparently tunnel a port from IPv4 to a remote IPv6 device?

At home, I am connected with an IPv6 address and additionally, my provider provides a NAT-like setup through which I receive a public IPv4 address that I share with other customers (the reason being ...
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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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138 views

iptables not forwarding vbox traffic

I have a vbox vm that i would like to give unfettered internet access to, and i have found instructions on how to properly forward traffic using iptables, as well as the recommendation that the vm ...
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1answer
94 views

why iptables is accepting all in INPUT?

As we can see in this, which is the default iptables on fedora 20 $ iptables -L INPUT --line-number Chain INPUT (policy ACCEPT) num target prot opt source destination 1 ...
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32 views

A more complex iptables rule

I want to make a script that sees if a number of connection attempts are made from one or more IPs ($CT_MULTIPLE_IP_THRESHOLD) in an ammount of time ($CT_TIME). If this happens, than in that ammount ...
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210 views

Access to a NATed LAN Network without public ip address using VPN and Apache Virtual Host

my question is: I need to access from the outside to a DVR that in my LAN has the local ip: 192.168.1.x I have multiple LANs located in 3 different places not connected each other at the moment. I am ...
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662 views

set https proxy with squid and iptables

have a Linux as router, eth0 (192.168.0.60) connect to LAN, eth1 (10.100.33.239) connect to Internet. squid works well, I can set 10.100.33.239:3128 or 192.168.0.60:3128 as proxy in web browser and ...
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564 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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261 views

Is Iptables blocking outgoing ssh connections?

I have been trying to do pulls from github and it keeps hanging. My iptables rules have no rules which block outgoing traffic but I cannot connect to github using either ssh or http. I can't even ...
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1answer
736 views

iptables + vpnc + Cisco IP Phone 7941

I have a Linux gateway with kernel 2.6.39 connected to a Cisco ASA 5500 with vpnc. I'm using iptables with masquerading and forwarding to give the LAN access to the tun0 device connected to the VPN. ...
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73 views

Forwarding all traffic to other server with iptables

Assume I have a sever with X.X.X.X IP address and a web server with Y.Y.Y.Y IP address. How would I forward web traffic from X.X.X.X to Y.Y.Y.Y using iptables? My servers run Linux and use iptables
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1answer
160 views

How does uTorrent can automatically forward port through Linux Net Filter based firewall?

I have dilemma: How it is possible that uTorrent shows on my internal machine with internal IP, that my connection is OK (green check in the bottom right of its window), while I never forwarded any ...
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1answer
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Is there a way to see when iptables was last changed?

Is there a way to see when iptables was last changed? I'm running CentOS5. I found this morning that the configuration is different from what I set 6 months ago.