iptables allow creation of rules to define packet filtering behavior.

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1answer
47 views

My iptables works the opposite from what I wanted

I have this set of iptables rules ... $ sudo iptables -n -L Chain INPUT (policy ACCEPT) target prot opt source destination LOG all -- 0.0.0.0/0 0.0.0.0/0 ...
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1answer
724 views

iptables - add rule for interface before it comes up

Right now I'm using /etc/rc.local to add some iptables rules on my Linux router on boot however some of the rules aren't added. I assume this is because the interface hasn't come up yet. This is what ...
2
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1answer
379 views

Masquerade not working sometimes

I have an issue with private network traffic not being masqueraded in very specific circumstances. The network is a group of VMware guests using the 10.1.0.0/18 network. The problematic host is ...
2
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1answer
221 views

Forward a host's network traffic to another host with the exception of SSH traffic

I am trying to redirect all the network traffic received in a old host to a different host. For that I created two new rules with iptables on the old host: echo 1 > /proc/sys/net/ipv4/ip_forward ...
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1answer
257 views

Randomizing the source port for new connections

Generally whenever source port is selected by a network application, it is selected in a sequential manner among the free ports like 32000, 32001 and so on. I want to randomize the source port ...
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1answer
198 views

Internet sharing with iptables: choosing which connection to share

I have a computer with two network devices (eth0 and wlan0), both connected to the internet (two different connections/isp). I'm trying to share the connection of wlan0 to another computer connected ...
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2answers
7k views

Block specific application with iptables [duplicate]

I have to harden a Linux desktop as an assignment in my college. But I got stuck at a specific problem: I have to control the outgoing traffic with iptables. It should be possible to prevent a ...
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1answer
3k views

Linux Fedora 19 - iptables failed to start

I've been trying to start the iptables firewall service, but it keeps failing. What's going wrong? # systemctl status iptables.service iptables.service - IPv4 firewall with iptables Loaded: loaded ...
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1answer
298 views

What are the pros and cons to editing iptables configuration file vs adding rules via the iptables command

I am working with a product on CentOS that occasionally needs to automatically add and remove rules from the iptables configuration. For example, during an update, we want to explicitly refuse ...
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2answers
5k views

Open a port in my CentOS

I'm trying top open a port on my CentOS machine: I edit the /etc/sysconfig/iptables file and add my rule: -A INPUT -p TCP -m state --state NEW -m tcp --dport 143 -j ACCEPT Then I restart the ...
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1answer
2k views

Local port forwarding automatically configured on boot?

I have software which needs to run as a non-root user, but needs to listen on port 80 and 443. With iptables, this isn't all that difficult: sudo iptables -t nat -A PREROUTING -i eth0 -p tcp ...
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1answer
387 views

Allow application specific access in iptables using guid

I would like to get Skype working with iptables and don't want to allow a huge range of ports thus I thought a solution might be iptables -A OUTPUT -m owner --gid-owner skypeGrp -j ACCEPT iptables ...
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1answer
139 views

Using iptables to block for specific services

I am using ipset in conjunction with iptables to create a list of IPs I want to block. I did this: ipset -N blocking iphash ipset -A blocking 124.205.11.230 // and repeated this line for all IPs I ...
2
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1answer
302 views

Linux nat/iptables configuration for a chain of peer-to-peer links

I have an experimental setup, of 4 Linux (CentOS) machines: All 4 machines are internally connected using different networks and can ping eachother directly connected interfaces. However only PC4 ...
2
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1answer
314 views

PPTP server with NIC aliases

I have set up a VPN on a VPS Server using PPTP. I have one NIC with two aliases. eth0 eth0:1 eth0:2 The 3 interfaces have public addresses. eth0 is a French IP, eth0:1 is UK, and eth0:2 is ...
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1answer
1k views

Need to access port on LAN through IPTABLES firewall on static IP interface

I have a Linux firewall with 3 NIC's. Eth1 is my LAN's default gateway and has IP address 10.1.2.250 and is connected to my LAN with IP range 10.1.2.0/24. Eth2 has IP address of 10.0.0.6 and gateway ...
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2answers
2k views

Checking the type of NAT

I have read that there are many types of NATs available like symmetric NAT, full-cone NAT, etc. If I am behind a NAT, is there any way to find out the type of NAT behind which I am currently working ...
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2answers
1k views

use iptables to allow incoming connections to some computer on port XYZ?

This is what I have: iptables -i em1 -A INPUT -j ACCEPT -p tcp --dport 9001 -v. If I want to accept incoming connections on port 9001 at this (127.0.0.1, or on the network 192.168.1.143) address, ...
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1answer
2k views

Limit the max connections per IP using OpenWRT?

Would the following iptables command on an OpenWRT router assure that no one client has more than 50 active connections? $ iptables -I FORWARD -m connlimit --connlimit-above 50 -j REJECT ...
2
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1answer
237 views

Bash script and Database

I have an iptables firewall in Linux bridge (RHEL5). I want to extract information like IP address, port number, port type, date and time, etc. from log messages using a Bash script, and then want to ...
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1answer
35 views

What is the purpose of -m, --match in an Iptables rule?

Many Iptables rules contain this -m or --match option, for example -I INPUT -p tcp -m state --state NEW -m limit --limit 30/minute --limit-burst 5 -j ACCEPT -A INPUT -p udp -m conntrack --ctstate NEW ...
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2answers
70 views

traffic routing with DNS

I have 2 gateway machines. 1 debian (main - 192.168.1.1), 1 centos (backup 192.168.1.2). There are 2 networks, 1 LAN and 1 WAN, going through "main" and from there over ISP1 "backup" is on LAN and it ...
2
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1answer
58 views

route some traffic in subnet to other gateway

I want to route traffic destined for 192.168.5.0/24 to a gateway of 10.1.10.24, but all other traffic to a gateway of 10.1.10.1. I tried: ip route add 192.168.5.0/24 via 10.1.10.24 but it seems to ...
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1answer
161 views

Routing problem from internal eth1 interface to an external ppp0 interface

I'm trying to connect two LANs using a ppp link. I had a basic network topology diagram but it didn't come out well. This can be seen here. Routing Problem ================ 172.20.0.0/16 ...
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2answers
424 views

how to check if iptable rule is working

I am new to iptables and networking in general, so I am experimenting with it. I am learning how to close ports; in particular I am trying to close a specific port on the host machine, so another ...
2
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1answer
118 views

On a router, what decides if a packet should be forwarded or directed into the router itself?

I'm trying to learn how packet routing works on a linux-based router (OpenWRT in my case) a bit better for setting up a few projects/just-learning. Referencing the below chart, I'll break this into ...
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1answer
391 views

Iptables can't forward from/to internal LAN with proxmox

I have an host with proxmox with single public ip and some virtual machine installed whit webservers and multiple doimains, the first VM is a proxy with haproxy that forward the request to other VM ...
2
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1answer
276 views

How do I apply iptables SNAT to packets bound for localhost (INPUT chain)?

I'm setting up a host that has two routes to the public internet: one via my run-of-the-mill home gateway router, the other via a gateway router on a semi-private network (AMPRNet on 44.0.0.0/8). Most ...
2
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1answer
144 views

iptables, what is truly open?

We have an RSA appliance, I've reviewed the firewall rules on this appliance to determine what ports are enabled. To me, it looks like its wide open; but the vendor states that I am wrong about this, ...
2
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1answer
672 views

How to completely block a website like Facebook?

I'm trying to block Facebook access from my home system (Ubuntu). I could add facebook.com to /etc/hosts, but that would only prevent accessing facebook.com. There are many other ways I could use ...
2
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1answer
71 views

Is iptables -p proto -m proto redundant?

I keep seeing "-p tcp -m tcp" all over the place, but it looks redundant. Why the '-m' if the '-p' already matches the protocol?
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2answers
314 views

Delay when iptables icmp rules take effect

I have setup my iptables to disable all incoming connection, i.e. :INPUT DROP [0:65535] When the iptables has been started, I run the following command to enable ping: /usr/sbin/iptables -A INPUT ...
2
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1answer
3k views

iptables based redirect captive portal style

What is a iptables set of rules that will force hosts connected to a access point, that try to access any website (port 80 of any ip or hostname) to be redirected to another device on the network ...
2
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2answers
454 views

Does IP tables need to be configured or is a stand alone firewall sufficient?

I have two desktops and a laptop running Arch Linux. I have not setup any iptable rules on any of the machines, and I am curious if I should. One desktop is only used in my home network and is ...
2
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1answer
818 views

Webserver establishing new outgoing connections from port 443

I've been trying to configure the firewall on a webserver running Apache using iptables commands. I took the approach of blocking all outgoing connections, except for those that are required. ...
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2answers
9k views

iptables: rules for tftp server

I have a tftp server which listens on standard UDP port 69. I have added following rule to my iptables to block everything except UDP 69. -A INPUT -i eth0 -s 192.168.1.0/24 -p udp -m udp --dport 69 ...
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2answers
143 views

ipset accounting information

I know that iptables keeps accounting information for ip traffic blocked or passed. However, it appears that when using ipsets with iptables, the accounting information is aggregated for the entire ...
2
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1answer
310 views

Mark packets between machines (client and router)?

Can I mark a packet on the client's OUTPUT chain and add an iproute policy on the router to route them via a specific gateway? This what I tried to do, but it isn't working. My client's mangle table ...
2
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1answer
53 views

IPTABLES chain need help for restriction

I have two network cards eth0:- 172.16.91.70 (External Zone) eth1:- 172.16.85.70 (Internal Zone) I have clients in my Internal Zone which can access the external network. The ping goes fine and can ...
2
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1answer
1k views

Port Forwarding using iptables on Open-Mesh

A quick overview for those who are unfamiliar with Open-Mesh: The system uses small wireless access points that automagically build their own mesh network. As long as one of the access points is ...
2
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1answer
425 views

iptables string not dropping packet from tcp streams while using conntrack and string

I'm facing an unusual issue where specific TCP steams are not getting dropped by iptables; instead it's like iptables is just removing those specific packets. We're getting the following traffic: ...
2
votes
1answer
5k views

How to setup iptables rules to allow skype

Here are my iptables rules to allow Squid to connect to a web server: # Accept internally-requested input iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT #http,https traffic only ...
2
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1answer
1k views

Why is a echo-request ping packet 84 bytes in the log of iptables?

When I log the length of a echo-request packet, iptables -A OUTPUT -p icmp -m icmp --icmp-type 8 -j LOG I saw the length was LEN=84, but in wireshark, the captured packet size was 0x60, why does it ...
2
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1answer
1k views

Allow IP packet forwarding from LAN to modem via router

In short: I'd like to be able to telnet to my modem from my PC via my router. There is a simple home router on 192.168.33.1. It is running OpenWrt. It has the following interfaces defined: br-lan ...
2
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1answer
896 views

How to config iptables for pppoe?

When I create the only rule disabling all input, iptables -P INPUT DROP I can not connect anything. So it looks like I should allow some incoming activity to get PPPoE working correctly. What rules ...
2
votes
1answer
108 views

Is there a way to redirect requests from foo.com to a VM on that server?

I saw a tutorial about redirecting client requests to a specific port to a VM inside the server using IPTables. Is there a way to redirect client requests for foo.com to a VM using only IPTables? or ...
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2answers
2k views

TOR Transparent Proxy - How does to the TCP redirecting work

I used an iptables ruleset based on the sample ruleset from https://trac.torproject.org/projects/tor/wiki/doc/TransparentProxy, Section Linux, Local Redirection Through Tor, to set up Tor as a ...
2
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1answer
729 views

iptables rule for limiting bandwidth in given time

Under Linux/iptables how can I limit the bandwidth in given time? ex.: don't limit the connection speed from 22h to 06h, but limit it from 06h to 22h, ex.: the max speed would be only 1Mbit/second! ...
2
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1answer
1k views

tun0+ iptables rule

I'm trying to figure out what that + sign means in a rule such as this: -A FORWARD -i tun0+ -j ACCEPT I'm pretty positive it relates to vpn. I noticed a /dev/net/tun interface and a tun0 in ...
2
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1answer
562 views

How would I go about getting UPnP working on a Slackware server/firewall?

I'm a long time fan of Slackware and I've always had a machine serving as my main server/firewall with the latest version installed. I have it now but I'm struggling to find information on how to ...