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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Expose a Reverse SSH Tunnel on the Remote server

I set up a Reverse SSH tunnel from my home computer to my work server: ssh -f -N -R 19999:localhost:22 remoteuser@server To connect to my home computer I have to first log in to the server and then ...
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confusing INPUT,OUTPUT iptables rules

Following is my iptables rules in Ubuntu. ╰─$ sudo iptables -S -P INPUT ACCEPT -P FORWARD DROP -P OUTPUT ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT -A ...
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170 views

Most secure way to have IPtables auto-loaded using Debian / Linux

I'd like to know the safest way to load iptables using Debian. Of course, I can use a script that uses iptables-restore : #!/bin/sh iptables-restore < /etc/firewall.conf but : 1) where is the ...
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5k views

How to permanently disable firewall in Red Hat Linux

I have followed the below steps to disable the firewall in Linux. After reboot, again firewall is enabled. How to disable firewall permanently? Login as the root user. Next enter the following three ...
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564 views

OpenWRT Firewarll INPUT Chain allowing everything?

I haven't done anything to my the default firewall rules except open a port for ssh from the wan and add the rules for OpenVPN as defined in this tutorial: ...
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73 views

Firewall init script

On Debian, what is the best way to start an iptables firewall script : /etc/init.d/firewall_script.sh in /etc/network/interfaces, add post-up /etc/network/if-up.d/firewall_script.sh Do you check ...
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410 views

Iptables deny access to a specific IP address not working

I'm not able to deny access to a specific IP address or deny access to a specific IP address range as well. My network environment is, I have one router which IP is (30.30.10.1) and second my hotspot ...
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873 views

How to block incoming traffic on a virtual interface?

How do I block all incoming traffic on eth0:0 but keep eth0 open? What I've tried is this: iptables -P INPUT DROP iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -i eth0 -j ACCEPT But this ...
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359 views

Iptables limit user access time and mac

I am trying to create an iptable chain to kick my daughter off her ipad during the night. With the mac only filter I can block access but when I add time it no longer works. Does anyone see an issue ...
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383 views

With iptables only allow certain outbound ports

Okay, I'm running a router with shibby tomato (linux based) v1.28-115 and have a bridge network setup (br1) that consists of a guest wifi. I want to only allow access to specific outbound ports... ...
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609 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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158 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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318 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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2answers
1k views

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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580 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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2k views

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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805 views

OpenVPN + Squid or another way of blocking advertisements/websites?

I have a personal VPN that I use on my tablet for public wifi protection. Adblock+ is limited on android in that you need to set up a proxy for it to work, and this isn't ideal. Before I started ...
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376 views

ICMP firewall policy for standard ubuntu desktop

For a standard desktop computer running Ubuntu 12.04 behind a NAT router, what ICMP packets should one accept in the firewall, say iptables? It seems there is often conflicting advice; some say block ...
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366 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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2answers
868 views

How do I route a port range in a linux host to a guest VM?

I am trying to redirect a certain port range in a linux host to one of its guest VMs. I would like for this redirection to apply to all the host's interfaces, including localhost. I was able to do: ...
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iptables rule for loopback interface lo

I want to test some network performance, where I need to use a tcp client to connect to a tcp server program on the same host, so I used localhost(127.0.0.1) however, when the TCP SYN is sent, it get ...
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1k views

Can't connect to SSH over VPN when using 3G only

I'm having a bit of a strange problem that I'm not sure how to debug/fix. I have a Raspberry Pi connected to a Windows VPN via either a wired interface or 3G dongle. With the wired interface I can ...
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1k views

IPtables Rules to Block IP Range

I've applied the following rules from a text file called "iptables.save" to iptables. But to my dismay, I found that the ip address 107.22.26.176 is still able to access my server via TCP. What did ...
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DD-WRT - Host-based forwarding

I would like to know if I can configure DD-WRT router, that operates as the server's network gateway, so support different forwards based on hostname (other than port 80). I've configured ...
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2k views

iptables port based routing

I've been Googling this for days with no success. I connect to a VPN from my server from time to time and I'm trying to configure my Debian server to only use port 80 and 443 through the VPN and all ...
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834 views

iptables block everything except http

I'm trying to configure my iptables to block any network traffic except HTTP: iptables -P INPUT DROP #set policy of INPUT to DROP iptables -P OUTPUT DROP #set policy of OUTPUT to DROP iptables -A ...
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1k views

Pinging an external server through OpenVPN tunnel doesn’t work

I have an OpenVPN server and a client, and I want to use this tunnel to access not only 10.0.8.0/24 but the whole internet. So far, pinging the server from the client through the tun0 interface works, ...
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686 views

Packets marked by iptables only sent to the correct routing table sometimes

I am trying to route packets generated by a specific user out over a VPN. I have this configuration: $ sudo iptables -S -t nat -P PREROUTING ACCEPT -P OUTPUT ACCEPT -P POSTROUTING ACCEPT -A ...
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395 views

Rate limiting traffic between specific hosts (based on their MAC) using iptables

I have setup a simple isolated network consist of following Linux based machines (simplified example): Node1<---->Router<---->Node2 Router's eth0 is connected with Node1's eth0. Router's eth1 is ...
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561 views

Reasons why ports below 1024 cannot be opened

I'm root on a machine I don't know how it was configured. I try to open SSHD on another port than 22 but it does not work. I changed the /etc/ssh/sshd_config file and added a new Port line extra to ...
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761 views

Difference default setting on iptables between CentOS 6.3 and Ubuntu 12.04

I would like to ask in ubuntu 12.04, there is no firewall settings by default? iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD ...
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374 views

internet connection gone after $ iptables -F INPUT

I have a PC with two Ethernet cards, and I was trying to configure my eth1, but when I typed $ iptables -F INPUT, the internet was gone on eth0. Does anyone has any idea how to get my internet ...
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133 views

Separating two networks

I have two routers, R1 and R2. R1 (a stock linksys router running dd-wrt) is connected to internet and is serving internet to a network of 5 devices/PCs running a DHCP server, with a network of ...
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801 views

Linux Iptables Routing

I need help with a problem. My setup is: CentOS (Router) eth1 18.0.168.1 255.255.248.0 eth2 145.165.34.1 255.255.254.0 Windows Server 2008 18.0.168.2 My problem is from the Windows machine, I ...
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867 views

Firestarter device not ready when booting Ubuntu

I am trying to get firestarter running on Ubuntu 11.10 and I am getting an error: Failed to start Firewall The device eth1 is not ready. Please check your network device settings and make sure ...
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4k views

Ubuntu 11.10 firewall/gateway - no client internet access

I have read many other posts but cannot figure this out. eth0 is my external connected to a Comcast modem. The server has internet access with no issues. eth1 is internal and running DHCP for the ...
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351 views

iptables Settings as WAN Input for Router

I have an eee running ArchLinux with wireless access to the Internet. I want to use it as the WAN input for an Asus RT-G32 router into which it is hardwired. The router in turn is hooked up to a ...
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iptables rules revert on Ubuntu

I'm using iptables on Ubuntu 10.04 and whenever I set iptables rules they will revert after a while. I set them with iptables -I INPUT or iptables -D INPUT and they work immediately and I see them in ...
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380 views

Is this firewall completely secure?

I'd like to know if there's any holes/flaws in this firewall setup. I want to lock down the server as much as possible so it is impossible to hack in to. The only services running are openvpn and ssh. ...
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1k views

loopback error, home network

I've setup my router to forward port 80 through to my computer, so I can access it from a dyndns.org domain. The domain and the ip both seem to be totally working, externally (can access it from ...
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2k views

DD-WRT OpenVPN client - cannot get “lan” connected device to route traffic

I have OpenVPN client setup on DD-WRT openvpn small. client connects and can use traceroute to verify everything is tunneling out the openvpn connection. ip_forward is 1. iptables -t nat -A ...
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1answer
157 views

How to setting up iptables for traffic fowarding on port 80 from specific sources

Im running a web server on port80, but i want traffic coming from ip 212.333.111.222 on port 80 to be fowarded to port 9020 on the same server that my web server is rinning at that is my sshd port
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258 views

One website not connecting over shared connection

A website is not opening on a computer that's connected via shared connection (not exactly "shared"). Pinging the website gets Packet filtered message. The setup of my home network is done by Ubuntu ...
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ipfw fwd in iptables or how to answer on non local adress

I have few servers working in scheme, for example, like this(sorry for my poor drawing): All servers have public IPs, I changed them for private in my examples. _______ |network| ...
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Is it possible to setup a NAT loopback on a router with a dynamic IP using iptables?

I've set-up a Raspberry Pi home server attached to my router. I have a dynamic IP. I can access the server within my network using the internal IP (192.168.0.8). I can also access the server outside ...
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Can't ping Subnet A from Subnet B with router between them

I experimented with subnetting in my home network and Raspberry Pi. The ISP Cable Modem has 4 eth-interfaces and 1 wlan interface which all seem to be switched together. The routers IP is 192.168.0.1 ...
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Can I track the CPU load that IPTABLES firewall is causing?

Since IPTABLES is a software based firewall, I am wondering if it is possible to log the exact load it is causing, cpu cycles, etc. On a small system I am sure it is trivial. But how about with ...
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OpenVPN without NAT

I'm trying to figure out how to route OpenVPN clients without using NAT/PAT. What I want to do is to route the IP address that they are assigned when clients authenticate to the OpenVPN server to the ...
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Iptabes and PSAD [closed]

I have a couple questions regarding my iptables configuration. First off I am still relatively new to iptables configurations, I am going over guides and books but progression is slow. When I ...