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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What are the iptables rules to permit ntp?

My server's clock is wrong because the firewall doesn't permit ntp traffic. What are the iptables rules required to allow the ntp client to get out and back? Any suggestions how to implement those ...
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With Linux iptables, is it possible to log the process/command name that initiates an outbound connection?

I would like to keep track of the processes that initiate outbound connections on a Linux desktop. The best I can come up with is this: iptables -A OUTPUT -m state --state NEW -j LOG --log-uid This ...
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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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pfctl port forwarding in Mac osx?

-A PREROUTING -s 10.0.10.0/24 -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 8080 -A PREROUTING -s 10.0.10.0/24 -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8080 -A POSTROUTING -s 10.0.10.0/24 -o ...
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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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No idea what is listening on port 80 in OS X

I'm on OSX Mountain Lion 10.8.3, and I've freshly rebooted my Mac. I want to start a service (like Apache on port 80), but there is already something going on with port 80: telnet localhost 80 ...
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iptables vs route

What's the difference between these two tools? Can anybody tell me what the main workflow of networking behind Linux (in relation to IPv4 packet filtering, NAT and IP routing table) is?
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How to negate a range in iptables?

I've seen people use the exclamation mark (!) in multiple examples, but when I try to use it I get an error. The rule I'm trying: -A OUTPUT -m owner --gid-owner 1006 -d ! 192.168.1.0/24 -j DROP The ...
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Mirror Port via iptables

I have a dedicated Linux (Debian 7.5) root server, with a number of guests set up. The guests are KVM instances, and get network access via bridge-utils (NAT, internal IPs, use the host as a gateway). ...
8
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SSH to Vmware virtual machine with NAT network [duplicate]

right now I am able to ssh to host over internet and ssh from host to the virtual machine. What I want to do is ssh directly to the Guest machine from outside. I tried to do this using iptables: ...
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Setup routing and iptables for new VPN connection to redirect **only** ports 80 and 443

I have a new VPN connection (using openvpn) to allow me to route around some ISP restrictions. Whilst it is working fine, it is taking all the traffic over the vpn. This is causing me issues for ...
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What does an empty iptables mean?

I’m using CentOS and when type in the following iptables command: iptables -L -v The output is as follows: Chain INPUT (policy ACCEPT 19614 packets, 2312K bytes) pkts bytes target prot opt in ...
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Sharing transparently proxied Internet connection with PS3

I am trying to play a Japanese karaoke game on a PS3 but the latency is just horrendous and downloading songs takes forever. One recommendation I got was to turn my laptop into a SOCKS proxy by ...
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How to configure a firewall on Centos using Vagrant and Chef

I've created a server box using Vagrant and Chef and everything is up and running correctly. However, when the box is installed from scratch the default iptables rules are in place and so I need to ...
6
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Disable or block outgoing email

To do web site testing, how can I disable or block the Centos server to not send out emails. Now, if I run in command line mail xxx@gmail.com I can send out emails. This is not good for website ...
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CentOS 6 - iptables preventing web access via port 80

I'm setting up a new web server with CentOS 6.2 and am not able to connect via the web. Everything looks set up correctly in httpd.conf and Apache is running, so I'm assuming it's an iptables issue. ...
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How to deliberately introduce a delay for incoming UDP packets

I want each packet (that match iptables rule) to be delayed by some fixed time interval. How to to this? Preudocode: iptables -A INPUT -p udp <more conditions> -j DELAY --delay 50000 # delay ...
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Open up firewall automatically to anybody who has successfully connected via SSH

I have a server which runs a few services. However, for security reasons, I configured the server so that nothing, except for SSH, is accessible from outside. What I'd like to do instead, though, is ...
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Deny all incoming connections with iptables?

I want to make some simple iptables rules to deny all incoming connections and allow outgoing. How can I do that?
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How to block sites with iptables

I would like to block sites using iptables. How do I go about this, and how do I ensure that the iptables rules are saved?
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IPv4, IPv6 and IPTables

I have just recently learned that even if I block all traffic to my webserver using iptables it is still vulnerable to external attacks via IPv6. In my understanding, this renders iptables-only ...
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Program to block an IP temporarily with iptables

Is there a program on Debian to block an IP address temporarily just by launching a command (specifying the IP and the duration)? With iptables/ip6tables alone I can create a rule, but I would then ...
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Blocking Skype using snort and iptables

I am trying to block Skype using snort and iptables. I read a lot of papers and blocked the port, keywords and patterns which Skype uses. But it is still not blocked. My question is: if Skype uses ...
5
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Rackspace Firewall/Gateway Setup

I have rackspace account and wish to have this sort of setup: Firewall/Gateway eth0 - Public IP (56.X.X.X) eth1 - Private IP (10.X.X.X) Ubuntu 10.10. Accepts connections from the internet and ...
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How do I configure DD-WRT to forward IPSec traffic to an internal server to support a road warrior configuration?

I use dd-wrt as my home router setup and that's been working fine. Now I wanted to figure out a way to be able to use my iPad to set up a IPSec tunnel to my home network while I'm on the road. PPTP ...
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How to configure port forwarding for an IP camera

I need to configure port forwarding for my IP camera so that I can access it from internet. UPNP is not supported on my gateway. My network configuration is the following: Gateway (Ubuntu Server 12) ...
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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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Does tcpdump bypass iptables?

I mistakenly setup open resolver DNS server, which was soon used for bunch of DDoS attacks originating somewhere from / to russia. For that reason I completely blocked port 53 on both DNS servers for ...
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Using iptables to redirect ip address

I have the requirement on a Linux system where the Linux device is using RSYNC to sync data to another Linux machine. This is working fine at the moment, however I need to move one of the machines to ...
4
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1answer
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IPTables module ip_tables not found for root

We got a custom build Linux distribution from a vendor, which is not shipped with iptables enabled. root@xxxx:~# iptables -L modprobe: FATAL: Module ip_tables not found. iptables v1.4.21: can't ...
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How to transparently tunnel a port from IPv4 to a remote IPv6 device?

At home, I am connected with an IPv6 address and additionally, my provider provides a NAT-like setup through which I receive a public IPv4 address that I share with other customers (the reason being ...
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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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dhclient unicast DHCPREQUEST excessive logs

I am using centos 7 with dhclient 4.2.5: $ uname -a Linux hostname 3.10.0-229.el7.x86_64 #1 SMP Fri Mar 6 11:36:42 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux $ dhclient -V Internet Systems Consortium ...
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iptables for transparent TCP proxy

Here's my situation. I have an iPad, a TiVo, and an dd-wrt router on my network, along with a machine that I'd like to use to sniff/decrypt draffic between the iPad and the TiVo. The iPad has an app ...
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Block a user from accessing internet on Linux

How do I block a user from accessing the internet under Linux? I'm trying the following: iptables -A OUTPUT -p tcp --dport 80,443 -m owner --uid-owner $USERNAME -j DROP Is that the right syntax or ...
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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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Access Apache server running in Fedora guest VirtualBox from host

I have trouble accessing Apache server from host. I’ve Fedora 15 VM VirtualBox installed on Windows 7. Within this VM I have Apache server running and working fine within the guest. Not sure what ...
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Load balancing with multiple gateways

I have to different ISPs, each on each own network. The main connects via ethernet and the secondary via wifi. The two networks have no relation at all. I just connect to them simultaneously. The ...
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How to use iptables to forward all data from an IP to a Virtual Machine

OK, in an attempt to get some response, a TL;DR version. I know that the following command: iptables -A PREROUTING -t nat -i eth0 --dport 80 --source 1.1.1.1 -j REDIRECT --to-port 8080 ... will ...
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Ubuntu 11.04 server iptables port forwarding

I'm pretty new to iptables. My server has two Ethernet cards (eth0, eth1) and an ADSL router that is in bridge mode connected to the eth0 which created ppp0 when dialed. I'm trying to forward ...
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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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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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Route outgoing VPN traffic through local transparent proxy

I have a Digital Ocean droplet (similar to an Amazon EC2 instance) running Ubuntu Server 12.04.3 x64 with both strongswan 5.1.1 (built from source) and squid 3.4.2 (also built from source) installed. ...
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How to block all ports except 80,443 with iptables? [duplicate]

Blocking all ports(in and out) is easy but it's hard with the word "except". I don't know any rules that satisfies the condition. PS: I know this question is nothing new. But in fact, I didn't find ...
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iptables - add rules not as root

One of our servers is being hit daily by a large number of spam bots. They're not able to post any spam, but they still try and end up slowing down the server for real users. To counter this, I have ...
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tc / iproute2, how to list the configuration

This is my first time using traffic shaping and I am wondering how I can list the rules I applied like you can with iptables? Walter
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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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Remove port aliases in iptables

How can I make iptables show me port numbers instead of aliases for well known port numbers (eg. http for 80, https for 443 etc.). Is there a way to make it show just port numbers at all times?
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bridge does not forwarding packets centos

I am using CentOS 6.5 64 and use xen to create a virtual machine (CentOS) ifconfig [root@CentOS ~]# ifconfig eth0 Link encap:Ethernet HWaddr 08:00:27:54:B3:FA inet6 addr: ...
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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