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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Match multiple strings in iptables

I have 2 strings, and i wish to queue the packet if it contains both the strings ( something like ("jsh"&&"gjhyg")), i tried following ways, but they don't seem to work: sudo iptables -A ...
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Configure iptables firewall to allow DHCP, DNS, HTTP, SMTP, FTP, IMAP, POP, and Squid ports – deny all other services.

Configure iptables firewall to allow DHCP, DNS, HTTP, SMTP, FTP, IMAP, POP, and Squid ports – deny all other services. 1 pc for router ( place firewall) 1 pc for server ( place web,dhcp,ftp,etc)
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Difference between iptables default policy to `DROP` and inserting a seperate policy in input chain to DROP all connections

I'm trying to DROP all incoming connections to my server, except from particular networks. At the same time I want to keep all outgoing connections from my server to external network (any network over ...
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4answers
550 views

IPtables keeps resetting rules and blocking almost everything

Every time I reset IPtables, the rules keep coming back in about 10 minutes, blocking everything besides port 22 and 80. When I do a "iptables-save", I see this I can't find out where it's coming ...
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69 views

iptables and router port forwarding

I need to access my home computer remotely using ssh. I have port forwarding set up on my router to send me to the appropriate computer on the local network. I have it working but viewing my home ...
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39 views

IP rule table look up does not seem to work

I have a sytem with three network interfaces. Below is the configuration that I'm trying to set up. wlan0 (its actually an WiFi AP interface) - other devices connects via this interface. net1 - ...
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1answer
534 views

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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1answer
87 views

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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171 views

How to block sites like facebook.com, google.com etc. for different users

I use iptables for other sites as: iptables -A OUTPUT -o EXTERNAL_IF -m owner --uid-owner USERNAME -d DESTINATION_WEB -j REJECT It works for most sites except ones having a large range of IPs. What ...
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363 views

ip6tables: how to handle periodically changing prefix?

My ISP provides me with native IPv6 (unfortunately DS-Lite for v4) and I'm using SLAAC for the clients in my local network behind a broadband router. As I don't trust the router (which is configured ...
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210 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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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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1answer
86 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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118 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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199 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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1answer
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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2answers
910 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
685 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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204 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
681 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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871 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: http://wiki.openwrt.org/doc/howto/vpn....
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124 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
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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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773 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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302 views

Restricting access to iOS apps based on time of day [closed]

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 day....
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129 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 1.2.3....
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56 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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63 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!” > /var/www/...
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1answer
551 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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228 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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296 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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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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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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1answer
56 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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102 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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377 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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95 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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280 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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1answer
369 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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927 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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115 views

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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2answers
632 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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1answer
255 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 ...
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527 views

Block All Traffic and Allow from Defined IP only in IPTABLES

I want to create a gateway firewall for my network . I want to block all the internal traffic on gateway and allow it from two computers only . On gateway --> eth0 is network card in gateway PC ...
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OpenWRT and iptables: redirect all traffic from ip1 to ip2

I'm aware of other questions with the same topic, but I couldn't get it to work. I'd like to forward inside my local network all traffic from ip1 to ip2. Only from inside the network, no outside. I ...
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344 views

Bitbucket SSH and iptables

I'm a newbie in iptables to be honest. I have some basic rules. Everything is blocked by default. iptables -t filter -F iptables -t filter -X iptables -t filter -P INPUT DROP iptables -t filter -P ...
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5answers
2k views

How to forward traffic using iptables rules?

I am new to iptables and I have been doing Google searches for a few days now without finding a good solution to this problem. I have computer A with a public ip address (say 192.0.2.1) that can ...
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234 views

Granular routing with iptables and iproute2 over VPN

On a host at my house I have a host for a VPN that I need for a couple of purposes. Living temporarily in Japan, it functions as a NAT for some devices so I can still use my NETFLIX and some other ...
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1answer
622 views

Asterisk server firewall script allows 2-way audio from incoming calls, but not on outgoing?

I'm running an Asterisk PBX on a virtual machine directly connected to the Internet and I really want to prevent script kiddies, l33t h4x0rz and actual hackers access to my server. The basic way I ...
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Equivalent iptables command on OS X 10.9

I want to redirect the tcp traffic temporarily to a custom port. On Linux, I use the following command: iptables -t nat -A OUTPUT -p tcp --dport 1935 -m owner \! --uid-owner root -j REDIRECT and to ...