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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Meaning of Bridge-Check in iptables flowchart

In the famous iptables flow-chart what does bridge-check exactly stands for ? I couldn't find any documentation. The only clue I found was while scanning the MikroTik RouterOS documentation ( ...
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Is it possible to know a user logged in on Ubuntu instantly?

In fact, I am trying to restrict access to some websites for different users. I asked the question: Restrict access to some websites for different users. The given answer is ok; but as the owner ...
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271 views

How to redirect all data through a proxy on Tomato?

My proxy is Squid as an external machine. My router is a WRT54GL with tomato. On the router, I wrote this for the firewall script. It nicely connects to the proxy, but when try to visit any page it ...
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1answer
50 views

How to apply ipfw rules to domains that resolves to multiple IPs?

Suppose I wanted to use ipfw to throttle uploads to youtube. The uploads are made to upload.youtube.com but this domain resolves into multiple different IPs (which also appear to change over time). ...
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179 views

not all packets forwarded by pptp VPN server

I have the following setup: +------+ +---------+ ppp0---------+ |router| | A +-----+---+-----+ B | | R | ...
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1answer
69 views

Route traffic to a destination to another destination using iptables

How to route traffic to a destination to another destination and receive response using iptables I have two vps on cloud. Lets say VPS-A and VPS-B. If a request to 8.8.8.8 generated from VPN-A, I ...
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50 views

Forward traffic from specific ip addresses to another port iptables

I can't figure out the syntax to forward TCP traffic from specific ip addresses to another port using ip tables. Lets say I want any TCP traffic from 1.2.3.4 to port 80 to be forwarded to port 81. ...
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100 views

Site to Site VPN - Openswan and CISCO A2A

Below is the diagram that the VPN connection between Openswan server and CISCO A2A. client A and B are remote hosts with static ips. client X and Y are behind the Cisco firewall. I can see ...
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2k views

Blocking access to a specific url

I have a lightweight linux device which I would like to block from accessing one specific URL. Instead of making the request to the external URL, I would like to return the contents of a local file. ...
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1answer
2k 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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2answers
271 views

Iptables, allow common ports, block the rest

I want to allow people to connect to ports 22, 80, and 443. Also I want to be able to do DNS lookups from my server. Here's what I'm trying: iptables -A INPUT -m tcp -p tcp --dport 1 -j ACCEPT ...
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1answer
283 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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20 views

Block all outgoing ports from iptables.

I have a windows xp machine running specific application which can be access by single port (27500). there is nothing else i want to access on this machine. If i block all outgoing ports from this ...
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1answer
96 views

iptables does not seem to be applying SNAT to packets sent on a raw socket

I'm writing packets from a user space program to my wireless interface wlan0. I've set up a SNAT rule with iptables as follows iptables -t nat -A POSTROUTING -o wlan0 -j SNAT --to 192.168.1.3 And ...
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1answer
599 views

CentOS 7.x iptables

I have manually edited the /etc/sysconfig/iptables file in my CentOs 7.x installation , I have two entries and two processes running at the respective ports. I am able to telnet/access port 2181 but ...
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1answer
352 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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1answer
83 views

Open ports in Ubuntu 13.10 server

Im setting up a realtime gameserver fps-game, and then i need to configure ports. Just to mention, i will setup multiple servers for this game on the same ip address, which means i must open multiple ...
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1answer
110 views

IPSet with IP6Tables ERROR

Can someone please solve my headache and tell me how to fix this? [root@www ~]# ip6tables -I INPUT -m set --match-set blacklist6 src -J DROP ip6tables v1.4.7: Couldn't load match ...
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1answer
3k views

Port forwarding with IPTABLES and VBox

I have a small problem with getting a proper configuration of iptables under Ubuntu. But before, let me describe the network configuration: I am using xDSL line terminated with modem+router+DHCP ...
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51 views

How to IP redirect all requests to public ip back to router

Using OpenWrt Backfire 10.03.1 on Linksys WRT54GL. Till today my ISP's modem used to loopback all traffic with self-destination IP back to itself. (for example if my WAN IP is 8.8.8.8 and I perform ...
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2answers
622 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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1answer
140 views

Restricting access to iOS apps based on time of day

I'm looking to set up something on my iPhone and iPad that works like SelfControl on my Mac. I get distracted by Facebook, and would like to restrict my access to it except during certain times of ...
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1answer
76 views

Port Forwarding with the real IP-address

How to implement port forwarding, so that would be displayed on the host real IP and non-IP machine, as it comes with SNAT DNET with IPTABLES The scheme is about the The machine-HETE with IP ...
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37 views

CentOS - ipTables

I have some questions about ipTables. Is it possible to open all ports between 2000 and 6000 and then have 2245, 5435,5434 closed? Is it possible to open some ports from a ip address? Eg. The only ...
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1answer
55 views

Need help converting some linux commands to OSX

I want to convert some linux commands into OSX. (Mavericks 10.9.4) root@bt:/# /etc/init.d/apache2 start (will "sudo apachectl start" do the same?) root@bt:/# echo “some Site Goes Here!” > ...
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388 views

squid proxy slow response

We are using the squid proxy in our setup and implemented as transparent proxy with user authentication. Before couple of days, while we are trying to setup the iptables the squid started performing ...
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146 views

Why doesn't SpeedTest.net Upload work in Windows when using a Debian-router?

There is a FTTx connection. I connect ISP cable to the WindowsXP pc, setup PPPoE. SpeedTest.net shows normal Upload / Download. Now I connect ISP cable to router with Debian 7.5 installed, set up ...
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167 views

How to correctly configure iptables on a laptop?

I have run these commands (tried switching the order too) because I want to set up a firewall on my laptop so that nobody can connect to it (except of course in response to a connection I've made): ...
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125 views

Iptables error :libipt_cgroup.so doesn't exist while using net_cls.classid in net_cls cgroup subsystem

In kernel document doc/cgroup/net_cls.txt, it introduces the function of net_cls.classid, and show an example of netfilter (iptables) using this tag to perform actions. the command of iptables is: ...
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768 views

udp client sending ICMP “port unreachable” when receiveing messages from the server

(Note: I moved this question from StackOverflow, because it's to be considered off-topic there, better fits here, and still unsolved) I have a udp client using luasocket, basically doing this (with a ...
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3answers
1k views

iptables LOG actio writes to STDOUT

when I use LOG action in some chane of iptables rules, I get the output both in STDOUT or STDERR of the xm console and in /var/log/messages. Is there way to make iptables to write only to log ...
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48 views

Should my server ever need to directly communicate with the NAT gateway?

What I mean by ``directly communicate'' Does it ever need to receive packets with the gateway's IP address as the source IP address, or send packets with the gateway's IP address as the destination ...
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56 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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23 views

Redirect external request thru VPN

I'm using Centos 5.4 and I'm trying to use the XMPP outside the company. But, the XMPP only works with the VPN. VPN connects and the XMPP become 10.0.2.49:5222 I tried to use iptables using this: ...
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175 views

iptables configuration on Windows Azure (CentOS 6.5) for endpoint load-balanced set

I created 2 VMs (CentOS6.5) on Windows Azure for Postgresql database and HA cluster, everything works fine except when I set iptables service on, the endpoint load-balanced set is down. for security ...
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91 views

Openvpn iroute traffic to internal network

I have a simple scenario like follows : 3 openvpn clients and an openvpn server , openvpn clients are (C1 , C2 and C3 ) openvpn server is (S1) behind the 3 clients ( C1 a network of 192.168.1.0/24) ...
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420 views

mirroring traffic with iptables doesn't work

i want to mirror specific traffic to ip 192.168.200.1 i use this solution : Mirror Port via iptables but when i enter following command, error occurs: iptables –I PREROUTING -t mangle -j ROUTE --gw ...
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Packets From Inside Not Being Forwared To Outside

I'm trying to forward internal packets to outside without success. iptables -t nat -A PREROUTING -i eth0 -p icmp -d "internal IP" -j DNAT --to-destination "external IP" iptables -t nat -A PREROUTING ...
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How can I check if an iptables rule already exists?

I need to add a rule to iptables to block connections to a tcp port from the Internet. Since my script may be called multiple times and there is not a script to delete the rule, I want to check if ...
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73 views

Redirect ports with iptables

I need to do redirect port 443 on all interfaces to 8080 on one interface using iptables on a box with 2 NICs. I also need to block pretty much anything else on those interfaces. Here is my iptables ...
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74 views

rails ssl setup on Amazon EC2

Environment Amazon EC2 CentOS Rails 4.0.4 SSL certificates installed Chef My Rails config In my environment .rb (staging.rb and production.rb) I added this config.force_ssl = true Started ...
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172 views

Allow internet access to intranet only users using Nginx on Ubuntu

I need to allow some users who only have access to the intranet to access one specific internet site. I'm doing this by using Nginx as a reverse proxy. To test this, I would like to block all internet ...
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64 views

How do I “socksify” IPv6 TCP connections?

For IPv4, one can use REDIRECT iptables target and redsocks/tcpsocks. How to do the same for IPv6? I've tried ip6tables -t mangle -A PREROUTING -d 2600:: -p tcp --dport 80 -j TPROXY --on-port 4455, ...
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211 views

Block all outgoing traffic for a User running Wine apps

Good day, I'm using a lot of WINE apps under Linux which work just fine, but one thing I am specifically looking for right now is to block their access to the internet (outgoing), with exception of ...
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167 views

block network access to a domain (ubuntu)

I have a few ubuntu servers in various geographies. I want to block all outgoing connections from all ubuntu machines (all processes) to several domains, e.g. www.server.com. I know iptables can block ...
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823 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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3answers
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outgoing ssh fails from only one machine on lan to outside network

I have multiple servers in my LAN (which I'll refer to as Box1), and they are all able to make outgoing SSH connections, except one that stopped recently, which I'll refer to as Box2 (actually, I'm ...
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216 views

Wifi sharing over eth0

There are a lot of tutorials how to share network connection with your usb wifi adapter and I tried lots of them but it is still not working. Can you please help me with my problem. Here is my network ...
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127 views

iptables error “FIX ME! implement getprotobyname() bionic/libc/bionic/stubs.c”

When I do this rule, the error shows up iptables -A INPUT -p tcp -m tcp -m multiport ! --dports 80,443 -j DROP I've also found some solutions. getprotobyname() just converts protocol names like tcp ...
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131 views

Cant connect to eth0 after wlan0 sharing with iptables

I wanted my Ubuntu server to act as a wifi hotspot. So I set up hostapd to allow wifi connections. I then setup dnsmasq to provide the DHCP settings. I then added the following iptables rules, so ...