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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Why is the TCP open but not the UDP?

I'm setting up a game server and I have a bunch of ports forwarded already (all in use). So I'm putting one into /etc/ppp/firewall-masq, which is full of iptables rules. The game server is served by a ...
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Preserve NAT mappings across reboot

My Linux router is able to reboot and reconnect all network interfaces pretty fast (~10 seconds, thanks to systemd and a SSD disk), and comes up with the same IP addresses. Unfortunately the reboot ...
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46 views

Trouble with last DROP rule in iptables

Let's say I want four ports to be opened for any incoming packets so I made this ruleset: #> iptables -L -v Chain INPUT (policy ACCEPT 20 packets, 1190 bytes) pkts bytes target prot opt in ...
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iptables do not block all traffic i want to mysql port

Need to block all incoming traffic to port 3306 but two ranges. The thing is I can connect from other ranges anyway!. Think my drop rule is ok. Why is this? ]# iptables-save # Generated by ...
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40 views

Port bridge with iptables

is there a way to achieve the same thing than bidirectional socat functionality with nc mkfifo backpipe nc localhost 42042 0<backpipe | nc localhost 1042 1>backpipe But only by using iptables ...
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136 views

Make application use specific network interface

I have an openvpn connection and I need it to work only for one application, this app uses an specific local port. I used route-nopull on my openvpn config file and then: ip route add default via ...
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42 views

Filtered port with virtual server setup on a NAT

I have a Symphony SY602 ADSL router and I want configure a dynamic DNS to access my system remotely. I made a NAT virtual server in routers configuration and this is what I configured: Server Name ...
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112 views

enable internet on openvpn tun - azure linux

I am trying to do this with OpenVPN TUN on an Azure Linux instance: -=Android Client=- --> -=VPS=- --> -=Internet=- Client connects but no internet access. Iptables commands iptables -t nat ...
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43 views

Why does iptables port aliasing work with only a single rule?

I have a service running on a particular port, but in order to make it accessible via a more memorable port as well as the normal port, I added an iptables rule that acts as a port alias: iptables -A ...
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2k views

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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16 views

Linux: Can user applications generate icmp messages?

I am using TOR and setting up a transparant proxy depending on users. I had trouble to constrain ICMP messages on UID. But I found an explanation for that on server fault. For the sake of privacy: is ...
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102 views

Open firewall port on Mac OS X

I need to open port 8181 on my Mac OS X. On Linux, I would do: iptables -t filter -A INPUT -p tcp --dport 1664 -j ACCEPT iptables -t filter -A OUTPUT -p tcp --dport 1664 -j ACCEPT How do I do this ...
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29 views

Can't connect to Monet DB hosted in RHEL5

I'm not a sysadmin, much less a RHEL sysadmin, but for some reason I have to make a few config changes in a couple RHEL servers. I have to set up a couple services in different RHEL servers and they ...
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1k views

Bandwidth limit by Port on iptables

What iptables function would I use to bandwidth-limit all traffic on port 566 to 2KB/s? I'm confused about exactly how to do this.
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428 views

Intermittent disconnections when using OpenVPN over SSH tunnel; possible iptables issue?

I've recently set up a Debian Wheezy server with OpenVPN to help out some friends in areas where internet censorship is a problem (including the blocking of VPN traffic in general). To overcome this, ...
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38 views

MASQUERADING a veth

I want to bind an application to a wifi interface that might loose connection and receive a new DHCPed IP on reconnect. The problem is that the application can only be binded to an IP address and not ...
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39 views

Why am I getting “FATAL: Ident authentication failed for user ”root“” after changing rails server to port 81

I was running my rails app on the default port of 3000. I opened port 300 with: sudo iptables -A OUTPUT -o eth0 -p tcp --sport 3000 -m state --state ESTABLISHED -j ACCEPT and sudo iptables -A ...
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43 views

How do I share my wlan0 internet connection to eth0 using command line and config files?

I understand how it is done using the GUI (1, 2, 3), but I need to do this manually using Linux tools/commands (iptables, eatables ...). What are the configuration steps and commands to use, ...
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35 views

SSH tunnel data from hostapd server to remote server

I've set up a small raspberry pi with hostapd to be a wireless access point. I'd like to have all connections from it ssh tunneled to a server in another country. I'm not overly sure how I'd do this, ...
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61 views

Route all packets on port 80 from inside a vm to kali linux on another vm

I'm trying to route all packets on port 80 to kali linux so that I can ssl strip them but I cannot see to setup the iptables correctly to force all the packets to go to my other Vm. [ Virtual Machine ...
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89 views

iptables on debian blocking git pull, http api requests etc

I am using IPTables on an API server to block all incoming traffic except for SSH, HTTP and HTTPS. I need to have full access on the loopback interface to run beanstalkd amongst other things, and need ...
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278 views

How to force Google safesearch on entire network

I've a problem filtering web searches on Google domains. Currently I've a linux openVPN Server running with openDNS "family block". I can block a lot of websites with dangerous content and it's ok. ...
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76 views

No internet through OpenVPN

I am having trouble with my OpenVPN setup. I have a Linode box with an OpenVPN server installed on it and I managed to get Tunnelblick to establish a vpn connection from my mac. I followed this guide ...
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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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71 views

Why my iptables configuration for port-knocking does not work?

I implemented the following iptables rules on my test server for a course. The firewall shuts down and I cannot access port 22. However, after knocking on the ports 1111, 2222 and 3333 in that order - ...
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160 views

Segregating/Separating a device (ATT 3G Microcell) from internal network without using DMZ

I would like to put the ATT 3G Microcell in an isolated network from a network that has the rest of my devices, by which I mean I want the ATT 3G Microcell to only be able to access the Internet, but ...
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118 views

Iptables rules to only whitelist SIP providers

I have an Asterisk box sitting behind an ADSL router/modem. There are no other services on the Asterisk box, just telephony. I am getting a lot of traffic which I think are SIP probes. I've ...
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4k views

iptables gives me the error “can't initialize iptables NAT”

I am trying to use iptables and it is giving me the following error root@vikkyhacks:~# iptables -t NAT -L iptables v1.4.18: can't initialize iptables table `NAT': Table does not exist (do you need to ...
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iptable definitions for routing and defence

I'm attempting to configure a firewall on my laptop that allows for routing. The main trick is, I don't want to allow for connections to be made that do not fall under the ESTABLISHED,RELATED ...
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6k views

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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69 views

Port mirroring without TEE

I have a home router running OpenWRT 12.09.1. The package list for this version does not have iptables-mod-tee. I am familiar that I could set up a port mirroring using: #-A POSTROUTING -t mangle -o ...
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40 views

Trying to configure iptables on Slackware 10

I am trying to configure iptables on a Slackware 10 machine. This Slackware version is required in my class - so I cannot upgrade it. After compiling it, I want to configure iptables - however, it ...
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128 views

Conntrack gets incorrect forwarding rules for outgoing protocol 41

I'm trying to forward protocol 41 (ipv6-in-ipv4) for an HE tunnel through a WRT54G running Tomato 1.28. Tomato 1.28 is running a 2.4 kernel that knows absolutely nothing about protocol 41, except that ...
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183 views

allow incoming ssh with openvpn client

I have set up an OpenVPN client on my home router. The moment the tunnel goes up, I can no longer ping my router from the internet using its WAN_IP. I would like to allow certain incoming connections ...
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1answer
90 views

Using IPtables to redirect IP address range to port range

I'm trying to set up an IPtables rule that will forward all packets to a /22 range to a single IP and port for debugging purposes. Based on the question here Using iptables to redirect ip address I ...
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2k views

unable to connect to localhost:80 after installing nginx

I just installed nginx by doing sudo yum install nginx and I'm unable to connect to it on port 80. I tried stopping iptables by doing sudo service iptables start and was still unable to connect. I'm ...
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98 views

Iptables redirecting

I have set up a Personal hotspot using Hostapd. But this hotspot is not connected to the internet but I do have Apache installed on it. What I am trying to achieve is to redirect all the clients (that ...
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1answer
53 views

When writing an iptables save file by hand, how does one calculate the packet-counter and byte-counter values?

I am attempting to write a 22MB iptables rule-set file, the very kind that is generated with the iptables-save command, except endlessly long. Understandably, this takes a prohibitive amount of time. ...
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864 views

What do these numbers mean in the output of iptable-save?

In the output of iptables-save # Generated by iptables-save v1.3.8 on Sun Mar 14 19:42:45 2010 *filter :INPUT ACCEPT [328764:37367248] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [324693:28884726] COMMIT # ...
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How can I efficiently filter Dos packets? [duplicate]

I have recently been the victim of some Dos attacks. The facts : I received a very high amount of packets saturating my connection and preventing me from accessing the Internet during one hour ...
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152 views

Iptables to forward HTTPS traffic to remote HTTPS proxy

My goal is to use Iptables to take all traffic going to my server on port 443 and forward it to a remote HTTPS proxy server. So basically if I was to use my ip of 192.168.1.142:443 as a SSL proxy it ...
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Open ports for Age of empires in ubuntu router using iptables

The purpose of this question is to learn how to correctly use iptables. As I am currently living in the dormitories in the University and I am using a small netbook as a router to provide wifi in my ...
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1answer
2k views

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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30 views

Special type of DMZ?

So I have a standard modem-router setup all great to go, my Modem gives an IP Address from my provider via DHCP according to my Mac address. All is good. However, I now want to expose a new virtual ...
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61 views

Set block time with iptables

I have the following rules in ufw, for iptables: -A ufw-user-input -p tcp --dport 80 -m state --state NEW -m recent --set -A ufw-user-input -p tcp --dport 80 -m state --state NEW -m recent --update ...
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131 views

Will an inbound iptables rule in ddwrt on port 443 break https?

I want to run a vnc repeater service on my home ddwrt router. Due to the possibility of friends/family asking for support in unknown network environments, I'd like the host-repeater application to run ...
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3k views

Limit incoming connections using iptables per IP

I need to limit access to some port per IP. Let's say 5 connections per minute - not more. I've seen iptables recent, connlimit and limit, but all of them are not fitting exactly what I need. ...
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45 views

Iptables intercepting traffic

I have 3 servers on the network (Server 1: 10.0.0.1, Proxy server: 10.0.0.2, Server 3: 10.0.0.3) and I would like to intercept the traffic going through the proxy server from Server 1 to Server 3. ...
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85 views

Iptables redirection to squid proxy server

I'm trying to setup filtering through a squid proxy however I'm having trouble getting my router to send all traffic to the proxy using iptables. I've currently got it setup such that there is the ...
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243 views

Is it possible to force DNS for certain devices with iptables?

I'm trying to use iptables to force DNS for certain devices (Shibby Tomato on Asus RT-N66U). I haven't found anything online describing such a configuration. The closest I could find was this: # For ...