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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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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245 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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85 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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1answer
95 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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66 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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326 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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117 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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46 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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63 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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144 views

How to forward ports through ssh and nat to another machine

I have a problem when using ssh port forwarding and nat simoultaneously. Situation: Machine A runs a webserver on port 8080 Machine B is a raspberry pi which works like a little router. It has two ...
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392 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
57 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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14 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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63 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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76 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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45 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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35 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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259 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
140 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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1answer
85 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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46 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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76 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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50 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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1answer
164 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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322 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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251 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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126 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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144 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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212 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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61 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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When writing an iptables save file by hand, how does one calculate the packet-counter and byte-counter values?

I am attempting to write a 22MB iptables rule-set file, the very kind that is generated with the iptables-save command, except endlessly long. Understandably, this takes a prohibitive amount of time. ...
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169 views

IPTABLES forward all ports except ssh

I have nat and packet routing working just fine, but I'd like to forward all ports except SSH to a static ip(192.168.0.3) What would be the correct iptables syntax to do this?
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867 views

Forwarding all incoming traffic on eth0 to go to eth1

I am trying to setup my raspberry pi to sit between my router and my modem. I'm basically trying to set it up as an intercepting proxy so that all web traffic goes through the proxy. I have the ...
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660 views

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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1answer
192 views

bind/named not working on UDP from external

This one is weird. I've set this up a long while ago, on a centos5. From what I remember, it used to work. For some time now, it's not. I've just been informed so no clue what changed when that made ...
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80 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
98 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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346 views

How to configure iptables correctly

I'm a newbie to linux.I just implemented the following commands in iptables which I found on a site for security (i don't understand much about how each rule works). The commands are as follows: ...
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1answer
81 views

Per application rules in iptable

Is there possibility to add rule via iptable for specific process name? Good explanation of why I need it is here: "Under Windows, this helps making the PC more secure. There are many ...
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137 views

Connecting to an SSH server behind a NAT

I am having trouble connecting to an SSH server behind a NAT on an ubuntu workstation. I've installed openssh package(both the client and the server) and forwarded port 22 through the NAT and tried to ...
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2answers
373 views

Is selective VPN routing worth it?

I want to setup routing tables on my RT-N66U router to selectively route traffic through a VPN. For instance, only Pandora requests would go via the VPN. I've found a way to do this with iptables: ...
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how to keep counters on iptables rule replace ?

When replacing a rule (by it's number), the counters also get reset. I can think of a scripting solution, though on very high traffic, this loses packets. Is there a way to keep the counters up? For ...
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1answer
104 views

Routing traffic over Vpn without NAT?

I want to tunnel traffic through my vpn but I just realized that my kernel does not have nat enabled ;( iptables -t nat -A POSTROUTING -s 10.20.0.0/24 -o eth0 -j MASQUERADE iptables v1.4.14: can't ...
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203 views

How do I block every connection except vpn and ssh without endangering the state of my vps?

I have some vps space but I get alot of scans based on what I see in iftop. I tried some iptables stuff but it gets tiring and useless to put all the ips that I see in the logs. I am wondering about ...
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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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89 views

unable to configure nat on centos 6.4

i have configured nat on my centos 6.4 on vmware workstation with the following cofiguration i have two ethernet adapters eth0 and eth1 eth0 has public ip automatically taken by dhcp eth1 has private ...
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152 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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109 views

Why does iptables restart cause connectivity timeout for about a minute?

I have a centos 6.5 64bit router with 3 nics. The box is configured to route 2 networks. netA - eth1 [ about 10 clients ] netB - eth2 [ about 100 clients ] provider - eth0 [ fiber to isp ] I have a ...
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160 views

UFW default rules… where are they?

In the tutorial on UFW here https://help.ubuntu.com/community/UFW it says that UFW uses the default rules if enabled and not configured. I checked the folder: /etc/ufw/ and the files I found ...