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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CONNMARK on rewritten packets

I have a host, on which I rewrite saddr and daddr of IP packets coming to it, this is done by the program, employing libnetfilter_queue. Basically it acts like proxy. For example, the packet comes ...
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Centos 6 server does not open ports

So after some battling and struggling with the firewall, i see that I may be doing something or the firewall isnt responding correctly there is has a port filter that is blocking certain ports. Okay, ...
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debian gateway using iptables

I am having problems setting up a debian gateway server. My goal: Having eth1 the WAN interface. Having eth0 the LAN interface. Allow both ports 22 (SSH) and 80 (HTTP) accessed from the outside ...
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50 views

List rules using iptables in a customized way

How to list the iptables rules in a customized way? Like: target protocol portnumber src dest the order could be changed but I dont want the name of protocols, just number (like 80 instead of http) ...
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586 views

Can't ping through default gateway

I have the following configuration: Routing table on M3 is: Destination Gateway Genmask Flags MSS Window irtt Iface 0.0.0.0 192.168.2.1 0.0.0.0 UG ...
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530 views

Install multiport module on iptables

I'am trying to install "fail2ban" on Cubidebian, a Debian port for Cubieboard (A raspberry like board). The following rule failed due to "-m multiport --dports ssh" options (It works, when i run ...
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439 views

Understanding how dnat works in iptables

I'm running 3 virtual machines with Fedora 19. The machine B is set up with two networks adapters and provides que channel between machine A and machine C. The machine A IP is set to 192.168.1.3 and ...
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Iptables redirect to localhost?

Suppose I have a network with a server routing all connections from inside the network to the Internet. How can I set up iptables so that instead of routing incoming connections to the Internet, it ...
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98 views

NM+iptables: How to forward port to shared wired connection?

I connect to my wireless network through NetworkManager. In addition I have another computer connected to the first one through ethernet. I'm using NetworkManager to share the wireless connection of ...
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259 views

redirecting traffic from a network interface to dansguardian

I have setup a Squid + Dansguardian parental control at home. I connected a WIFI router to the Ubuntu machine and share that network for my kids' mobile devices. The parental control works fine on the ...
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323 views

Redirect PROXY traffic to test box using IPTABLES

Marked this as answered. I'm going to pass on trying to get this to work. It was only for testing. I'm currently using a proxy server (squid) that's listening on port 8080. Users' browsers are ...
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109 views

Drop IP fragments of a certain protocol

When conntrack is active, the iptables stack never sees a fragmented IP packet, only the reassembled one (source), so the -f test never matches. If I want to block any fragment I could set ...
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iptables FORWARD rule

I'm running 3 virtual machines with Fedora 19. The machine B is set up with two networks adapters and provides que channel between machine A and machine C. The machine A IP is set to 192.168.1.1 and ...
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509 views

Can't ping after ip change

I'm running 3 virtual machines with Fedora 19. The machine B is set up with two networks adapters and provides que channel between machine A and machine C. The machine A IP is set to 192.168.1.1 and ...
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118 views

iptables rule to block traffic not specified in all other rules

Is there a way to add a rule in iptable to block traffic not specified/covered in all other rules ? I know that we can use ! to block specific ports and ip addresses but there are just too many rules ...
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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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241 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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252 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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226 views

Disable SSH remote tunneling

I need to restrict SSH tunnel functions. Users should not be allowed to create remote tunnels but only tunnels to localhost. I tried to setup the whole thing in the SSH configuration but I can only ...
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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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How can I port forward an LAN port to a WAN Ip with iptables?

Using iptables on my router (dd-wrt), I'd like to forward requests to the router on port 64738 from the LAN to an IP (192.168.10.14) on the WAN. This is the opposite of the norm (forwarding a request ...
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1answer
5k views

How to allow FORWARDing with firewalld on a Fedora 19 router

I've just installed Fedora 19 and I'm using firewalld instead of iptables, but I'm having difficulty interpretting the new terminology. I have 2 NICs. One is specificed ZONE="internal" and the other ...
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108 views

iptables as a proxy

I'm not sure how to start better so i'll be straight. I have to travel to a foreign country, but i need access to a server that is local to my hometown network. I have a DD-WRT router with only my PC ...
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162 views

Server can't be accessed

I have a server I rent from OVH and I rebooted it and now I can't connect to it, OVH responded with "The server has started (login is requested on the screen) but inaccessible by the network (not ...
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Using iptables to give an LXC container a routable IP

I'm using Docker to manage LXC containers. At the moment Docker configures the underlying LXC container with host-only routing and then uses iptables/DNAT to punch holes into the container, making it ...
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Port based NAT-ing with iptables

On eth0 port we have public IP, and eth1 we have IP 10.31.0.1 which provides DHCP and Squid service. Ports 8080,53,67,80,443 are open. Now for an application we have to open 1521,8443 ports so that ...
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CentOS 6.4 and alternate SSH port not working

I've got a CentOS 6.4 machine and would like to change the default SSH port, and followed these instructions: CentOS Wiki After making those changes (including the "semanage port -a -t ssh_port_t -p ...
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Forwarding RDP connections with iptables

I have a workstation that runs Windows 7 as the host, and Ubuntu Server 12.04 in VMware on a bridged network. Both have their own static public IP address. However, I only have one hostname to work ...
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Linux Traffic Control of internet downlink with router as a client

I'd like to shape my internet downlink bandwidth in a bit peculiar way. My linux box at home acts as a router and a torrent client (and other downloads), making my router a router and client inside my ...
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309 views

Iptables output with options unknown

I have been learning and studying up on iptables and port forwarding. There is a sample iptables output I can't decipher. It has the options --dir, --pol, and -m. Although I am familiar with -m it ...
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1k views

Fedora's firewalld vs iptables

I am on Fedora 19. Is my understanding correct that as long as firewalld is up and running (and properly configured using firewall-config) the contents of the /etc/sysconfig/iptables has no meaning? ...
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1k views

Bandwidth limit by Port on iptables

What iptables function would I use to bandwidth-limit all traffic on port 566 to 2KB/s? I'm confused about exactly how to do this.
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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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Seting up IPTables to forward multiple GoPro cameras

I have an interesting problem that involves multiple GoPro cameras. Basically, I need to have the ability to communicate with multiple GoPro cameras via a single network. The challenge is that the ...
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Cannot open port 8080

I'm running a VmWare with an application under JBoss starting up on port 8080. I'm able to access the app from outside the VM if the iptables are off. However, I must turn on iptables due to some ...
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Force certain applications to use VPN

For a few days now, I've been trying to force only certain applications to use a VPN. I've thus far found it pretty simple to either force all applications to use it, or no applications to use it. ...
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521 views

Internet access to host behind firewall using ssh tunnel

My goal is to give host behind firewall access to the internet. Below you can find brief description of network [internet] <-> [proxy] <-> [A] <-> (firewall) <-> [B] [A] - ...
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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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DNS set correctly but website unreachable

I have the (sub)domain elo.bernardinuscollege.nl, which has a DNS A record that points to 54.225.118.87, which is correct (checked it with telnet, which indeed returns the right IP). For some reason ...
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How to do port forwarding/redirecting on Debian?

I have two questions. Question 1: My debian machine has interface eth3 with ip 192.168.57.28. If someone tries to connect to 192.168.57.28:1234 how do I redirect the request to another machine: ...
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Setting up two ADSL lines for home/business use

As a follow-up to this question which is still unresolved. I have two ADSL routers with different providers connected to different phone lines to the internet. As shown in the diagram. These routers ...
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need iptables rule to accept all incoming traffic

For my test environment i want to accept all incoming traffic, can someone please give me the iptable rule to be added. My current iptables -L -n output looks like this Chain INPUT (policy ...
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1answer
665 views

Unable to ping my VirtualBox VM

I've installed a VirtualBox VM from http://virtualboximages.com/CentOS+6.4+x86_64+LAMP+Server+VirualBox+VDI+Virtual+Computer. My VM has access to internet, and I can ping the host. I've set a static ...
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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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1answer
451 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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2answers
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what does “-m tcp” mean in this iptables rule?

Firewall configuration written by system-config-firewall -A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
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Forward connections on 0.0.0.0:80 to 127.0.0.1:9091

I'm trying to set up a tor-relay. In order to allow tor to present a static web page explaining what it is I want the server to listen on port 80 and 443. In order to allow tor to use ...
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255 views

Can't reach web server from local virtual network

I have installed a couple of virtual machines. Some uder Windows, some under Fedora Linux. On one of the Fedora machined I've installed Apache web server. I have setup server name in httpd.conf to ...
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iptables MASQUERADE and SNAT together

Good people, I have a network having the following setup eth0 10.216.11.41 internet facing eth1 192.168.0.4 internal network interacting with other machines within the internal network. Id like ...
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110 views

IPTABLES to block sites on browser

I am trying to block a specific IP address from being accessed using the browser on my system. I added a simple rule as below iptables -A OUTPUT -d <IP> -j DROP The site gets blocked in the ...