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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Samba ports still closed even with iptables rules flushed and disabled

I’m trying to install Samba on a server running CentOS 6 with WHM/cPanel, and I’m having some trouble with ports. This is a brand new system as of yesterday, and I haven’t yet started locking down ...
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why my nat iptables rules dont work with marked packets?

System: debian squeeze, Linux server 2.6.32-5-amd64 #1 SMP Tue May 13 16:34:35 UTC 2014 x86_64 GNU/Linux, iptables v1.4.8 lsmod | grep iptable iptable_security 2176 0 iptable_mangle ...
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about CentOS 7 apps & Driver

im using pc for several years but never tried Linux so im quite noob in this field. im using Autodesk maya, Nuke & will learn houdini very soon. i found that linux works faster for this apps so ...
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iptables subdomain port forward

Hello i know i can setup iptables to forward to an other ip when a port is given Example: user enters domain.com and it shows site other user types domain.com:28015 and it connects to a game server ...
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IP tables rule: 0x06/0x02 [on hold]

Can I replace SYN,RST SYN with SYN,RST,ACK SYN,RST,ACK in iptables rule? What will happen If I change it ? # iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp- mss-to-pmtu
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port forward in INPUT level

I want to change the destination port of the ipv6 packet in the INPUT level. So I tried to use ip6tables with nat in the INPUT level but seems this command does not work # ip6tables -t nat -I INPUT ...
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10 views

Use Ubuntu Iptable to route public ip to pc in private network

I am currently set up a Ubuntu server as a Router which has two network interface. eth0 -> Connecting to public internet ( 10.10.1.78 ) eth0:1 -> 10.10.1.79 eth0:2 -> 10.10.1.83 eth0:3 -> 10.10.1.81 ...
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3answers
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iptables catches on DENY but not on ACCEPT place prior to it in the chain

I have a weird problem with my iptables firewall: If I set two consecutive identical rules, the first is ACCEPT and the second is DENY, the incoming packet is denied (and logged as such). How is it ...
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6 views

equivalent of iptables rule in ip6tables

I m newbie in the iptables. I have the following iptables rules in the source code of a project iptables -t mangle -I PREROUTING ! -i br0 -p TCP --dport 45 -j MARK --set-mark 0x1000 iptables -t nat ...
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iptables directing traffic through vpn

Networking newbie. I have two interfaces on the host: eth0 and tun0 from my OpenVPN client. The IP addresses are: eth0 192.168.1.22 tun0 10.1.0.8 Question 1 For outgoing traffic by changing ...
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what the “!” means in the iptable rule

what the "!" means in the following iptable rule iptables -I inacc ! -i br0 -p UDP --dport 69 -j ACCEPT I think is related to the interface br0. I think it mean any interface except the br0 Am I ...
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1answer
23 views

iptables problem in Evil Twin

I've been looking into the Evil Twin method and I found this steps: Creating AP airmon-ng start wlan0 airbase-ng -e PrivateWIFI -c 9 -v mon0 at0 Configuration ifconfig at0 up ifconfig at0 ...
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1answer
21 views

How to block docker-mapped ports with a firewall from outside the host without messing up docker routing inside the host?

I have a docker container running on a host with some port mapped to a port on the host. docker run -d -p 9009:9009 someserver I want this machine firewalled off from the internet except for 80, ...
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22 views

Route certain traffic through tun0 and some through eth0 based on destination IP

I have the following setup, a linux box with 2 physical interfaces sitting between my modem and my router, on eth0 it is set to DHCP and get an IP from the modem, I then run a DHCP server on eth1 so ...
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20 views

Docker tunnel traffic on specific port via VPN

Not sure if this is docker specific or a general networking question. I'm running a Debian Jessie server with serveral docker containers. My understanding is that docker creates a virtual interface ...
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1answer
18 views

What does the column after destination in iptables overview show?

If I print the iptables overview with iptables -L I get the following output: $ sudo iptables -t nat -L Chain PREROUTING (policy ACCEPT) target prot opt source destination ...
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Why doesn't iptables accept IP address as source?

The command sudo iptables -t nat -A PREROUTING -i eth1 -s ! 192.168.178.30 -p tcp --dport 80 -j DNAT --to 192.168.178.30:3128 fails with Bad argument `192.168.178.30' Try `iptables -h' or ...
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1answer
25 views

Man in the middle using iptables

I wish to test a subsystems which communicates with another subsystems via tcp. I have used the following: "iptables -A OUTPUT -p tcp --dport "+port_number" -j DROP" to stop the traffic on a port ...
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1answer
13 views

iptables limit number of outgoing connections on a port

I'm currently using the following to limit the number of incoming connections on port 9001 to 900. iptables -t filter -I INPUT -p tcp --syn --dport 9001 -m connlimit --connlimit-above 900 -j REJECT ...
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tcpdump capturing packets only when interface is specified

I have tried 3 different ways of capturing a stream of packets coming into my server. Two of them work and the third does not. I am trying to determine why it is missed by the third approach: ...
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22 views

WordPress won't load unless iptables is disabled

I am running CentOS 6.6 using nginx. WordPress will not load unless iptables is disabled. I tried to add the 9000 port for fastcgi, but that did not work. I am guessing it has something to do with ...
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14 views

Use IPTables FORWARD for NFS

I have this topology [R1] -> [F1] -> [Server] I need to pass ssh, web and nfs traffic through F1 to Server using iptables. It's quite easy with ssh and web but I'm stuck with nfs. I have set static ...
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1answer
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Confusion about the `conntrack` extension of `iptables`

The iptables-extensions manpage has this to say about the conntrack extension (emphasis mine): This module, when combined with connection tracking, allows access to the connection tracking state ...
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1answer
26 views

How do I know if certain iptables extensions are available and enabled?

I was reading this: https://help.ubuntu.com/community/IptablesHowTo#Allowing_Established_Sessions It says "If the line above doesn't work, you may be on a castrated VPS whose provider has not made ...
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1answer
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Make traffic go one-way by using iptables

I have a network topology: [C1] - [R1] - [R2] - [C2] C1-R1 network is 192.168.100.0/24 R1-R2 network is 10.9.8.0/30 R2-C2 network is 192.168.200.0/24 What I need to do is to make C2 be able to ...
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79 views

CS:GO SRCDS and iptables (firewall)

I have very strange problem. This morning I wanted download, install and host small server for CS:GO on my VPS. I used this tutorial: ...
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8 views

Port Forwarding using iptables

I have the following problem: I have two servers. I can connect to server A trough the internet. But I also want to connect to server B. How can I use iptables, that if I connect to server A over ...
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1answer
29 views

Where do port knocking services listen for incoming knocks?

I'm trying to understand how a port-knocking daemon is able to monitor for knocks, independent of the firewall rules (e.g. accept/drop/reject packets). I've installed knockd, which listens for lets ...
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11 views

Limited network connectivity when SSHing through an OpenVPN tunnel

I have setup an instance of OpenVPN with a public IP to allow access to a private subnet on Amazon EC2. I am able to SSH onto machines on the private subnet through OpenVPN but when I do I have ...
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Linux iptables DNAT on incoming packet without conntrack (stateless)

In my linux box 10.20.1.1, i got two UDP apps binded on port 46000 (App A) and 36000(App B) respectively. The apps communicate with two UDP servers bindeded as 10.10.1.1:36000 (Srv X) and ...
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How to redirect traffic to a fixed IP address in Fwbuilder

I'm new to fwbuilder and I want to redirect all incoming wifi traffic to my web server. I tried many iptables command but I've failed so I came up to GUI firewall. Can anyone suggest how to do it?
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Manage NAT using a tool

I have a Raspberry Pi on which I had previously installed Raspbian and am now installing another version on again. It is mainly used to be a test maschine for small programs and primarily as a NAT ...
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19 views

OpenVZ cotainer and NAT

I have been trying to days to solve my NAT issue with OpenVZ. I have used their guide on their website/wiki, however I just seem to be unable to get it to work. My Linux box is running on CentOS 6 ...
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iptables: Routing requests to localhost:8080 to google.com

I am trying a simple routing rule that would forward the requests to localhost:8080 to some external address (ex google). I added the following rule : sudo iptables -t nat -A PREROUTING -p tcp -d ...
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Guest as Virtual machine connection to Host

I have guest run on my machine on qemu with configuration: /usr/local/kvm/bin/qemu-system-x86_64 -enable-kvm -cpu host -smp 8 -hda ${TEST_VIRT_ENV_IMAGE} -m 4096 -netdev user,id=user.0 -device ...
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35 views

Forward all traffic from one Linux interface to another?

I have a virtual ESX interface "eth1" that I want to act as a gateway for connections, and then route all of the traffic from these connections out of my "eth0" (WAN) interface. Here are my ...
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130 views

Connecting my Xbox 360 to my Raspberry Pi 2 to use an OpenVPN connection

Here is my brief setup: Xbox360 Raspberry PI 2 running ArchLinuxARM (alarm) The raspberry pi's main ethernet port has a cable connecting directly to my main router The xbox has a cross-over cable ...
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34 views

Tor Middlebox: How to check if there is a DNS leak?

I created a tor middlebox. Laptop plus WLAN. Creates a WLAN AP all traffic from that AP should be routed into tor. But I am not sure, if the DNS requests are not leaked. How can I check that? This ...
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43 views

tor middlebox: How to route traffic through a socks proxy automatically? iptables routing wlan

I built a tor middlebox. It is an old laptop without screen, creates a WLAN and every traffic on that WLAN is routed into tor. my iptables script: iptables -t nat -A PREROUTING -i wlan0 -p udp ...
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ssh: connect to host * port 22: Connection timed out

I have CentOS 7 running on a VPS machine and after a computer restart, I could no longer SSH to it. $ ssh -v <IP> OpenSSH_6.6.1, OpenSSL 1.0.1e 11 Feb 2013 debug1: Reading configuration data ...
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Traffic redirection with Rasperry Pi router

I use a Rasperry Pi (running raspbian) as a wi-fi router. It redirects traffic from the Ethernet wire (eth0 - wire + ppp0 - L2TP connection, lx2tp used for it) to wlan0 (USB wi-fi dongle, hostapd used ...
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33 views

Connecting router traffic to sshuttle tunnel

I am using sshuttle to get cleanly out of a questionable hotel wifi connection. I have a little travel router and would like to use it as well, briding my laptop's sshuttle connection so I can connect ...
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44 views

CentOS as home network router: IPTables Port Forwarding failure

I have currently set up a home server with a CentOS 6.6 installation on it. The server has two NIC interfaces which I'm using it as my router and DHCP server. Here's a diagram showing the network ...
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21 views

NAT Rule for PPTP Port Forwading

I'm under a very heavy firewall where only very common ports such as 21 and 80 are open. I installed PPTP on my own dedicated server (a Debian Linux) and I`m trying to connect it using Windows, but ...
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https proxy setup in NAT-ed clients

I have network setup as follows: I have 2 PCs. A and B. A is connected to Internet, and A and B is connected by local network. B can also connect Internet through A by NAT setup. In A, the NAT setup ...
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Create a VPN tunnel from ethic to wlan0

I have a lan network of which all internet traffic has to be routed through a openVPN tunnel. I use a RPi, and have setup ethic with a DHCP server, and can connect clients. Currently I use a lan0 to ...
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iptables default rules understanding

What does the last part in the following rules means in term of traffic that is allowed in (dtp:domain, bootps) ? From my research I understand that bootps is bootstrap and dpt is destination port but ...
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IPTables and SIP Proxy-Authorization Header

Is it possible for iptables to check SIP packets for Proxy-Authorization headers, and if there's more than one header in a SIP packet, modify the packet so only the latest Proxy-Authorization header ...
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51 views

port forward from host to libvirt guest virtual machine that is bridged to the host nic

I am having no luck getting access from the outside to a http server running on my network in a Debian virtual machine that was created through libvirt. This what my network looks like: PC1: running ...
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49 views

Forwarding some ports and websites from “eth0” to “wlan0” with IPTables

I have eth0 and wlan0 devices in my work laptop. eth0 access the company's network and it comes with the whole firewall rules and so on. So I’m unable to use Skype, Google Hangouts and other things I ...