iptables allow creation of rules to define packet filtering behavior.

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15
votes
4answers
43k views

Output traffic on different interfaces based on destination port

My question is basically the same as Only allow certain outbound traffic on certain interfaces. I have two interfaces eth1 (10.0.0.2) and wlan0 (192.168.0.2). My default route is for eth1. Let's say ...
39
votes
8answers
13k views

Block network access of a process?

Is it possible to block the (outgoing) network access of a single process?
10
votes
2answers
5k views

How to restrict internet access for a particular user on the lan using iptables in Linux

Let's say there are two users on the LAN, A and B. How do I restrict user A from internet access using iptables rules and saving the rules so that after reboot, they are still effective. And suppose I ...
14
votes
2answers
7k views

Per process firewall?

I've been reading around but can't seem to find a way to create per-process firewall rules. I know about iptables --uid-owner but that only works for outgoing traffic. I've considered scripting ...
7
votes
6answers
25k views

iptables to block https websites

I wish to block a few websites that also run upon https, like facebook, twitter, and gmail, in my organization. Squid is not supposed to be used here as per the orders from higher management. We can ...
23
votes
3answers
91k views

Iptables to allow incoming FTP

I want to allow incoming FTP traffic. CentOS 5.4: This is my /etc/sysconfig/iptables file. # Generated by iptables-save v1.3.5 on Thu Oct 3 21:23:07 2013 *filter :INPUT ACCEPT [0:0] :FORWARD ...
8
votes
1answer
2k views

Dual network connection

I have a usb cellular modem and a Home LAN connection on my Ubuntu 10.10 box. Both work independently. I want to know how to have both connected at the same time, and be able to specify which ...
11
votes
3answers
18k views

Only allow certain outbound traffic on certain interfaces

I have rather an odd issue. I have a server with two network interfaces eth0 and eth1. Each are connected to a different network. Each network has a internet gateway. The server has various outbound ...
26
votes
5answers
41k views

Viewing all iptables rules

I just wanted to ask if there's a way to view iptables rules in a bit more detail I recently added masquerade to a range of ips iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE ...
6
votes
2answers
9k views

iptables port-mirroring

I need to be able to get a copy of packets received on port 8001 to port 8002. I have tried the following but I get an error that --tee is undefined. sudo iptables -t nat -A PREROUTING -p TCP -s 127....
5
votes
4answers
21k views

Whitelist IP's in CentOS 7

I want to setup CentOS 7 firewall such that, all the incoming requests will be blocked except from the originating IP's that I whitelist. And for the Whitelist IP's all the ports should be accessible. ...
3
votes
1answer
3k views

iptables/pf rule to only allow XY application/user?

I think there is no iptables/pf solution to only allow an XY application on e.g.: outbound tcp port 80, eth0. So if I have a userid: "500" then how could I block any other communications then the ...
12
votes
1answer
10k views

Linux as router with multiple internet providers

Linux as router: I have 3 Internet providers, each with its own modem. Provider1, which is gateway address 192.168.1.1 Connected to linux router eth1/192.168.1.2 Provider2, gateway address 192.168.2....
10
votes
2answers
36k views

iptables --set-mark - Route diferent ports through different interfaces

Short story, 3 interfaces, eth0 (LAN), eth1(ADSL), eth2(4G). eth0 -> eth1: Works (ports 80, 443, 4070) eth0 -> eth2: Doesn't happen This is a graphical representation of the idea: Port 80 & ...
11
votes
1answer
9k views

Configuring OpenVPN to use Firewalld instead of iptables on Centos 7

I need some help configuring OpenVPN on Centos 7 using firewalld. I used iptables on Centos 6.5 and only had to add the following lines to /etc/sysconfig/iptables: -A POSTROUTING -s "10.0.0.0/24" -...
9
votes
4answers
30k views

Set some firewall ports to only accept local network connections?

Basic firewall question: How do I set up the firewall on a system in a LAN so that some ports are only open to connections from the local area network, and not from the outside world? For instance, ...
4
votes
1answer
3k views

multigateway routing for specific src port

I have two gateway to access internet, somehow I want to load balancing it, so far its working, but some connection or service need persistent gateway IP to be used, so the client should never change ...
5
votes
1answer
3k views

How iptables tables and chains are traversed

I know linux has 3 built-in tables and each of them has its own chains as follow: FILTER: PREROUTING, FORWARD, POSTROUTING NAT: PREROUTING, INPUT, OUTPUT, POSTROUTING MANGLE: PREROUTING, INPUT, ...
3
votes
2answers
2k views

How can I Forward a subDomain to a specific port?

My apologies if this has been asked before. I haven't found an adequate solution so... yeah. When a specific domain, "example.com" is accessed, I want it to act normally. In other words, it should go ...
4
votes
1answer
6k views

iptables: how to allow traffic from redirected port

I have a web service running on debian 7 and listening on port 8080. I want to redirect 80 to 8080 for inbound connections and allow only port 80. Here is my iptables configuration: root@localhost:~# ...
3
votes
2answers
650 views

RELATED,ESTABLISHED state in iptables

What do the words 'RELATED' and 'ESTABLISHED' individually signify in RELATED,ESTABLISHED state in iptables?
0
votes
1answer
3k views

viewing firewalld logs via remote login to CentOS 7 server

I have firewalld installed in a remote CentOS server. When I log into the server over the internet as root, I type the following command to access the firewalld logs: journalctl --output=json-...
32
votes
1answer
25k views

What is the difference between -m conntrack --ctstate and -m state --state

I'm reading this howto, and there's something like this: We can allow established sessions to receive traffic: $ sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT ...
29
votes
2answers
22k views

Reply on same interface as incoming?

I have a system with two interfaces. Both interfaces are connected to the internet. One of them is set as the default route; a side effect of this is that if a packet comes in on the non-default-route ...
23
votes
3answers
71k views

How to ensure SSH port is only open to a specific IP address?

This is my /etc/sysconfig/iptables: It has two ports open 80 apache and 22 for ssh. # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. ...
8
votes
2answers
27k views

How can I configure syslog.conf file, to log iptables messages in a separate file?

How can I configure /etc/syslog.conf file in order to save log information about iptables in a specific file. I want to save these information separately, so I can extract what I want easily and ...
20
votes
1answer
11k views

Is it better to set -j REJECT or -j DROP in iptables?

There's an example of iptables rules on archlinux wiki: # Generated by iptables-save v1.4.18 on Sun Mar 17 14:21:12 2013 *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT ACCEPT [0:0] :TCP - [0:0]...
8
votes
3answers
21k views

IPTables - Port to another ip & port (from the inside)

I currently have a NAS box running under port 80. To access the NAS from the outside, I mapped the port 8080 to port 80 on the NAS as follow: iptables -t nat -A PREROUTING -p tcp --dport 8080 -j DNAT ...
13
votes
3answers
45k views

iptables: allow certain ips and block all other connection

How do I allow certain ips and block all other connection in iptables?
15
votes
3answers
2k views

Can I limit a user (and their apps) to one network interface?

As the title really. I've actually got two scenarios to apply this: Multiseat Desktop: two network connections both with internet gateways and two accounts doing bandwidth-intensive tasks on each. I ...
9
votes
2answers
24k views

Port forward to VPN Client?

I've run into a bit of a puzzle and haven't had much luck finding a solution. Right now I am (sadly) connected to the net via Verizon 3G. They filter all incoming traffic so it is impossible for me to ...
9
votes
1answer
5k views

Why doesn't my iptables rule work?

I have two interfaces on my VPS: eth0 and eth0:0. I want to block incoming packets on port 80 on eth0:0 using iptables. I tried this, but it doesn't work: iptables -A INPUT -i "eth0:0" -p tcp --...
7
votes
4answers
10k views

Help configuring a custom log file for iptables

I'm trying to log dropped packages to a custom file instead of /var/log/messages. To achieve this, I have added these two lines at the end of my configuration file: -A INPUT -m limit --limit 5/...
7
votes
2answers
5k views

Terminal commands equivalent to NetworkManager's “Use as Hotspot” option

I'm making a gui application which will control my laptop in order to make it act as a wifi hotspot. I may change distributions so I want to find a solution which will work generally for all ...
7
votes
2answers
10k views

What is the tun network interface for?

I noticed when running ifconfig that there is a network interface called tun0 and it has an ipv4 address. A bit of research shows that it is a tunneling device, but I don't really know how it's used, ...
3
votes
1answer
4k views

Settings when using a bridge

I have a bridge set up between my physical Ethernet interface, eth0, and the virtual interface for OpenVPN, tap0. The bridge has an IP address, and the machine can be contacted on that IP address from ...
9
votes
1answer
216 views

What is the difference between -j DROP and -j STEAL?

I often see that people set STEAL target in iptables rules. It's possible to get this target by installing (on debian) xtables-addons-common and xtables-addons-dkms. I was curious why people prefer ...
7
votes
2answers
6k views

Iptables: matching outgoing traffic with conntrack and owner. Works with strange drops

In my iptables script I have been experimenting with writing as finely grained rules as possible. I limit which users are allowed to use which services, partly for security and partly as a learning ...
5
votes
1answer
6k views

iptables: recent module

I am using the "recent" module to prevent port scanning, such as: -A INPUT -i eth0 -m recent --name PORTSCAN --update --seconds 60 -j DROP -A INPUT -i eth0 -p tcp -m tcp --dport 22 -j ACCEPT -A INPUT ...
4
votes
2answers
385 views

set connection limit via iptables

I want to limit the IP traffic of an application (AceStream Player). The problem is that I get disconnected, if too many IP connections are established. Does anyone know, how to use iptables to limit ...
2
votes
1answer
4k views

system wide SOCKS5 Proxy

I connect to my Server on the internet using ssh -D 3128 user@rootserver.com. If I am right I thereby open a SOCKS v5 Proxy to my Server. Using firefox and FoxyProxy I can now add this to my proxys ...
14
votes
2answers
35k views

Why are some ports reported by nmap filtered and not the others?

I'm scanning a server which should have a pretty simple firewall using iptables: by default everything is DROPped besides RELATED and ESTABLISHED packets. The only type of NEW packets allowed are TCP ...
7
votes
1answer
10k views

Why are incoming packets on a TAP interface seen with tcpdump but not with iptables?

A program injects packets on a Linux TAP interface (these packets are coming from a virtual machine). Specifically, these are DHCP requests (so they're UDP). I can see the packets with tcpdump but not ...
6
votes
2answers
10k views

set packet rate limit via iptables

I have a packet rate limit (max. 10 per seconds) which is set by my internet provider. This is a problem if I want to use the AceStream player, because if I exceed the limit I get disconnected. How ...
4
votes
1answer
4k views

How can I redirect all traffic except local through external proxy with iptables in dd-wrt?

I have a router with dd-wrt. I have a firewall running to direct all traffic through an external proxy. It works great except that it also redirects local Ips and my proxy does not allow Ips, so I can ...
3
votes
2answers
193 views

Why doesn't iptables receive the marked packet?

I was learning the ping command options. In that I found the -m option to set the mark for a packet. The below command sends the packet with marking of 10 to the 192.168.2.65. ping -m 10 192.168.2....
2
votes
0answers
101 views

debugging iptables when tunneling one VPN through another

I seek to tunnel one SSL VPN (F5, running on my debian laptop==client) through another (OpenVPN, running on a debian linode==server), but lose all client networking (including, e.g., ping) after the ...
2
votes
1answer
146 views

Redirect secondary network interface traffic along with port forwarding to tun0 (OpenVPN) using iptables

I have a NAS server which I should do port forwarding for it in order to make its services accessible from internet. However my ISP is blocking ports, so I've managed to buy myself a cheap Ubuntu VPS ...
1
vote
0answers
166 views

Howto configure linux router to allow clients to use maximum bandwidth?

The problem is that I'm always limited on the final client machine to about 1/3 (one third,about 200/300kb) of the internet hotspot bandwidth when testing download speed with wget. I have configured ...
1
vote
0answers
80 views

How to send packets coming from a second router on a particular port back to the router, using iptables not a route

I have a Linux server which runs a particular service listening on a single TCP port. The Linux server connects to the internet using a PPP connection and also acts as router for a local network using ...