Red Hat / Fedora :: Properly Define Iptables To Accept Traffic Only From Specified Hosts?
Nov 8, 2010
I have an log monitoring application that is listening on port 514 to receive events only from certain hosts.In order to control this,I've tried set up iptables to define those hosts that are allowed to this application. Here is an example of the script that contain the commands:
iptables.sh -> Code: iptables -I INPUT -p tcp -s 192.168.0.10/24 --dport 514 -j ACCEPT
iptables -I INPUT -p tcp -s 192.168.0.15/24 --dport 514 -j ACCEPT
...
[code]....
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Oct 25, 2009
What commands do you use to set the INPUT, OUTPUT, and FORWARD chains in iptables to ACCEPT?
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Jul 16, 2009
How come FC11 is set by default to reset the IPTables firewall to ACCEPT across the board each restart?
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Apr 26, 2009
I've tried both the firewall interface that comes with Fedora and Firestarter, neither can configure as I want. So I think I'm going to have to do it by hand. In this laptop I have one 10/100 Nic and one wifi connection, at times either of them can be connected to the network. How can I configure IPtables so that any traffic is allowed out, nothing is allowed in (other than std stateful firewall replies), no icmp and that the fw logs any attempts to connect to the laptop?
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Oct 13, 2010
I've got a Slackware 12.2 system that I'm trying to get to accept traffic on a given port, let's say 34521. When I use canyouseeme.org, to see if that port is responding, it is not.
I've put in an iptables entry to accept traffic on that port, is there anything else I need to do?
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Mar 4, 2011
Why does ping see audit.median.hu as 127.0.0.0, and why does host -t a audit.median.hu see it as 193.68.35.149? audit.median.hu is just an example site [hosts ads, etc.]
I just have a caching nameserver on my Fedora PC:
I configured my DNS server addresses in the Network-Manager Applet: 127.0.0.1, 8.8.8.8
Even with Wireshark, I can see it:
So the big question: Why don't the host command or my web browser recognize that I have modified audit.median.hus IP address?
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Dec 25, 2008
in my iptables script I define the environment like this:
Code:
# ENVIRONMENT
# Private interface
IF_PRV=eth1
[code].....
if I give the IF_PUB interface the DYNAMIC IPaddress assigned by my ISP how can I define it in IP_PUB and also the NET_PUB so I can then use it for the firewall rules.
exemple rule:
Quote:
iptables -t nat -A POSTROUTING -s $NET_PRV -o $IF_PUB -j SNAT --to $IP_PUB
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Jan 26, 2010
I have a service, which calls other services. I need to verify that my service is hitting the right end points of the other service, since the end points of the other dependent service are specified in configs, and are different for different stages - development vs production. Is there any tool which can tell me what end points are being contacted from my host?
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Oct 29, 2010
my iptables Policy is Drop..my server ports is open just for httpd,ssh .Is there any rule which can allow all connection from a specific program for ex. i want to scan an ip Address ports.as you know nmap connect to every known port to see if that is open or not so, if i want to allow nmap to connect, i need to include all ports for that, or i can allow connection from localhost to outside in all ports .my server is very secure . i dont want other programs (probably a backdoor) use those ports to connect outside i want to know is there any ability in iptables which can rule connections by name of program like "Allow any Connection from /usr/bin/nmap to everywhere " ?
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Apr 19, 2010
I'm building a simple(?) socket server using threads to serve up a few requests. The spec is such that I have to listen to three ports at once, so I decided to use pthread to create three separate threads that would wait for connections, then spawn new threads to handle them.
The problem is that when I do this, for some reason the program never enters the wait loop and instead terminates (All three threads did get created since the messages get printed properly.) It gets to the line which prints "???", but not the line after the accept() call.I don't see an open port when I check for one either so I'm 99% sure they're terminating.Basically I have a main() method which has three calls to pthread_create, which should result in three threads being run that all wait for connections (listenOnPort). After each thread creation I print some info to make sure it's actually being created.
By the way, when I just run listenOnPortwithout threading, the server appears to enter the loop correctly and seems to be waiting for requests. It's only when I run the functions as threads that the problem seems to happen.The source is attached below. Any help will be appreciated. Much of the code is borrowed from a website (I can't post it because I am new here.) You need not worry about the handler_ methods because those are just methods that are run by the threads themselves.
Also--the original source was in C and I changed it to C++. Should I just use C?
server.h Code: /*
* server.h
[code]....
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Mar 17, 2010
i used the angry ip scan software and found alot of the public ip addresses on our network are accessable from outside when they are not suppose to, For eg printers/ pcs etc. to make a start on locking down the network i was wondering if anybody knew th iptables command to add a rule which blocked all incoming traffic to specific ip adresses on the network and to a range of ip addresses.
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Jun 3, 2011
I have installed ubuntu on Vmware.I work in Lan environment and I have 2 local linux servers in my office.I have installed nagios on ubuntu.but nagios doesnt show other hosts in office.How to do I add other hosts in the office in nagios so that I can monitor network properly?
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Jan 23, 2011
I did some playing around changing up the configuration of my server and now cannot pass traffic through to port 22. I have since restored everything back to the way it was but am still not able to ssh into the server.
nmap only shows port 80 and 5222 open. Both ports that I want open. However I am unable to get 22 to pass.
iptables -nL shows
http://www.theprepared.com/images/tech/iptables_nL.PNG
netstat -an |grep 22 shows
http://www.theprepared.com/images/tech/netstat.PNG
I've tried clearing the routing table with the following which did no good.
ip route flush table main
Can somone point me in the right direction?
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Feb 11, 2011
I set up iptables but it is blocking my SSH set up. I did allow it by opening port 22 but it did not work. Here is my config:
Code:
iptables -F
iptables -P OUTPUT ACCEPT
iptables -P INPUT DROP
iptables -P FORWARD DROP
### this should allow SSH traffic
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
How do you allow SSH through the iptables firewall?
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Jul 6, 2010
I do $ sudo iptables -A INPUT -p TCP -i eht0 --destination-port 80 -j ACCEPT
and then $ sudo ufw enable but I still get no internet traffic. What is wrong? Shouldn't opening port 80 to TCP allow the packets though my firewall?
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Jun 28, 2011
I'm having problems configuring my virtual hosts file properly The site [URL]... opens on http and https The site 10.0.1.3/myapp/ works
I am trying to redirect all traffic from [URL].... to [URL].... while maintaining access to [URL]....
[Code]....
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Feb 25, 2010
I'm looking to use Linux (Ubuntu 9.10) as a network bridge between two subnets. I can configure iptables to permit all traffic on eth0 (subnet 1) to pass to eth1 (subnet 2) but before transmitting that traffic I want to perform further analysis. Is it possible within iptables or via a third-party product such a pyroman, to write a "hook" that then directs that traffic to another application installed on the same host?
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Aug 20, 2010
I have an Untangle Box - which for those that don't know is a modified Debian Lenny used as a router, proxy, filter and much more - It has three physical interfaces on it eht0 (incoming traffic), eth1 (Outgoing to LAN after traffic filtered), and eth2 (Called a DMZ NIC, as Untangle can be used as a router). There is also a tun0 interface setup by Untangle for VPN (Not using the Openvpn in Untangle because I need bridged a bridged VPN and this is not an option in Untangles offering), a br0.eth setup by untangle to bridge eth0 and eth1 for traffic flow through as it is inline from router to switch and not acting as the router itself, and a br0 interface that I have setup by bridge script bridging eth2 and tap0 to run OpenVPN as a bridged VPN.
The routes on the machine are as follow:
Code:
untangle:~# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.100.0 * 255.255.255.0 U 0 0 0 br.eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 br0
192.0.2.0 * 255.255.255.0 U 0 0 0 dummy0
192.0.2.0 * 255.255.255.0 U 0 0 0 utun
untangle:~#
I don't see a default route listed here, however, I do have Internet connectivity on the Untangle box itself. I also know that by script to bridge the tap0 and eth2 interfaces adds a default route through the gateway on the network that eth2 is connected to. So the lack of a default route is somewhat puzzling to me, I do have the gateway set through the web based admin interface Untangle offers.
The iptables rules are as follow:
Code:
untangle:~# iptables --list-rules
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-N alpaca-firewall .....
There was an addition output rule in the alpaca-nat-firewall rule that said DROP outgoing interface eth2, I removed that rule with no change. I can ping out from the Untangle server to the eth2 LAN, I can access resources in the eth2 subnet. But I cannot get any reply from the server from anything either in that subnet or not. If I run iftop I can see the incoming traffic form my ping but the Server sends out no reply. I think this is a firewall issue. I can access the server by connecting to the IP assigned to the eth0/br0.eth interface which is in my main LAN. I am also attaching a crude diagram of the previous setup and the new setup (Previous setup used a different server for my bridged VPN).
Is there a rule I can add to ensure that traffic coming in on an interface goes out the same interface? Do I have a rule blocking incoming traffic to eth2/br0? Do I have one blocking sending out on eth2/br0? Do I have a default rule that is killing the traffic on eth2/br0 and I need to add an accept rule for traffic coming in on eth2/br0? I tried adding an accept rule for traffic coming in on br0, but it didn't work. I tried an output rule, but that didn't work, but I may have been bungling these rules as I do not fully understand the syntax and function and body of an iptables rule. The exact original iptables information before I modified anything can be viewed at [URL].
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Feb 21, 2011
I need to set OUTPUT to DROP, and add the outgoing traffic one by one, but I couldn't do it. My current config is as follows:
Code:
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
:RH-Firewall-1-OUTPUT - [0:0]
-A INPUT -j RH-Firewall-1-OUTPUT
#previously ESTABLISHED,RELATED comm is ok
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
#80 is ok from all
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
If I change OUTPUT to DROP in :OUTPUT ACCEPT [0:0], I don't get any response from a server running in that box. I am using RHEL 5.5. Now, asking Red Hat is not an option: I have the license but I don't have support license.
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Aug 11, 2011
I am trying to configure iptables for only HTTP and HTTPS traffic. I start by blocking all traffic, which works, via:
Code:
iptables -F
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP
I then try to allow HTTP and HTTPS on eth0 with these commands, which does not work:
Code:
iptables -A INPUT -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT
Code:
iptables -A INPUT -i eth0 -p tcp --dport 443 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 443 -m state --state ESTABLISHED -j ACCEPT After these commands I should be able to access the internet. Does anyone know why this is not working?
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Jan 13, 2010
We host a web server in which we are hoping to implement some form of traffic redirection based on source IP address, and I am wondering whether the squid proxy built on iptables would be capable of managing this task? Essentially we are trying to redirect traffic from specific set of source IP ranges to a "Your IP has been restricted" type of page at a different IP/FQDN.
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Apr 4, 2010
a good IPTABLES protocol to reject all incoming ssh trafiic except for a single IP or IP range?
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Sep 20, 2010
I have a strange iptables issues. I have just built a new Debian install and starting adding some real basic rules (see below) the problem seems to be that the localhost itself can't get any returning traffic. That is, it seems to be allowed outgoing traffic but not the connected, returning traffic. Ordinarily allowing Established Connections would resolve this, see the rule below, but it hasn't. Why this doesn't work. Removing the last DROP in the INPUT chains obviously makes the traffic work!
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -j ACCEPT -p tcp --dport 22
iptables -A INPUT -j ACCEPT -s x.x.x.x
iptables -A INPUT -j ACCEPT -s x.x.x.x
iptables -A INPUT -j ACCEPT -s x.x.x.x -p tcp --dport 80
iptables -A INPUT -j ACCEPT -s x.x.x.x -p tcp --dport 8080
iptables -I INPUT 1 -i lo -j ACCEPT
iptables -A INPUT -j DROP
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Jan 11, 2010
I'm using Ubuntu server 9.10 with 2 NICS (Internet-router-eth0, eth1-LAN). I use iptables to generate rules for 20 computers, but when I execute the script, ALL TRAFFIC DROPS, including the server. What am I doing wrong?
Code:
#!/bin/sh
#eth0 192.168.0.50 - connected to Internet
#eth1 192.168.1.51 - connected to LAN
#192.168.1.52 - workstation1
#set default policies
iptables -P INPUT DROP
[Code]...
iptables -A FORWARD -i eth1 -o eth0 -p tcp --dport 80 -s 192.168.1.52 -j ACCEPT. The reason I'm doing this is, I just want to open necessary ports in the server and restrict LAN usage.
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Jan 6, 2011
I need to configure iptables to block incoming traffic (except specific ports), but allows all outgoing traffic.
I am able to block incoming traffic, but doing so also prevents outgoing traffic (tested by telnet [URL] 80)
The following was used:
iptables -A INPUT -p tcp --dport ssh -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -I INPUT 1 -i lo -j ACCEPT
iptables -A INPUT -j DROP
Also, even allowing NOT SYN requests still prevents outgoing traffic.
iptables -I INPUT 1 -p tcp ! --syn -j ACCEPT
Another point:
# modinfo ipt_state
modinfo: could not open /lib/modules/2.6.18-028stab070.14/modules.dep
How to install ipt_state module on ubuntu?
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May 3, 2011
I'm currently using a homemade Python script to parse script kiddie IP addresses from logfiles.To this point, I've simply been DROPping any requests from these IPs using iptables.I thought it might be fun to redirect their traffic back to them, but as I am not an expert at iptables, I was wondering if I should use FORWARD or PREROUTING.
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Jun 19, 2011
how to redirect network traffic to a new IP address using IPtables. I am using Baffalo router and the rtos used is DD-WRT. Basically, I want it so that any connection going through my router to a specific IP (say, 192.168.11.5) will be redirected to another IP (say, 192.168.11.7) so any outgoing connections made by a program that is attempting to connect to192.168.11.5 will instead connect to 192.168.11.7.
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Jul 31, 2010
I was just wondering if using a non-smp kernel would be ok on a older p4 system with no x. I am wondering due to some functionality in IPTABLES that is broken in the SMP kernels ( -m owner --sid.pid,cmd-owner).
Could someone that is running a NON-SMP kernel advise as to whether the support for -m owner --cmd-owner is working in iptables with those kernels? Also, could someone advise me if running a NON-SMP kernel is even advisable? The machine will not have x.
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Jun 1, 2010
Im running a web server on port80, but i want traffic coming from ip 212.333.111.222 on port 80 to be fowarded to port 9020 on the same server that my web server is rinning at that is my sshd port
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Mar 25, 2010
I am new to iptables. We have two Squid proxy servers running in "non-transparent mode" (172.16.0.1 and 172.16.0.2). Currently users have to configure the proxy server they want to use by configuring them in their browsers. Recently I saw an example for redirecting web traffic to a single transparent proxy server.
-A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128
-A PREROUTING -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 3128
Can anyone modify this rule to accommodate my current setup of two proxy servers running in non-transparent mode. i.e Redirect web traffic to the 172.16.0.1-172.16.0.2 ip range.
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