iptables allow creation of rules to define packet filtering behavior.

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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 ...
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1answer
2k 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 ...
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2answers
321 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 ...
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1answer
699 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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7k 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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124 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 ...
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1answer
237 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 ...
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51 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 ...
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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 ...
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1answer
400 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: ...
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1answer
4k 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 ...
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1answer
1k views

How do I route different users over different OpenVPN tunnels in Linux?

The setup: I have multiple, static-key OpenVPN client/server configurations, labeled "client1", "client2", and "client3" with server/client IPs 10.10.1.1/10.10.1.2, 10.10.2.1/10.10.2.2, and ...
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819 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 ...
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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 ...
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1answer
784 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 ...
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1answer
107 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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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 ...
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1answer
663 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! ...
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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 ...
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1answer
14 views

Per user routing on wifi

I'm using vpn but i want to have one user that could access network not through vpn but using my real ip address. The problem is that all solutions i found by quick google'ing, for example this ...
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1answer
32 views

Iptables rule to drop packets to and from local network

I want to set a virtual machine on laptop, but I don't trust the guest system fully, so I would like to block it's access to local network (to network 192.168.0.1/16 or 10.0.0.1/8 or ... the other one ...
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How to unwrap a tunneled packet in iptables/netfilter and process the tunneled packet

I have a specific question regarding the Linux netfilter/iptables interaction. Let's say I have an IP packet P1 inside of another IP packet P2 (that is, P1 is tunneled). Now, the question is as ...
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42 views

Two ISP and redirecting traffic

I have a gateway with two ISP connected to eth0 and eth2. There is also a eth1 with local network. I'm trying to group some services in one interface and some in the second: incoming traffic 1 ...
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1answer
65 views

NAT box with multiple internal and external interfaces

Similar questions have been asked before but my setup is a little different and the solutions to those questions are not working. A have a CentOS 6 server running iptables with 5 interfaces: eth0: ...
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83 views

How to explain strange kernel messages?

I have a server running on Debian Wheezy 3.2.68-1+deb7u1 x86_64. Lately strange records in /var/log/messages appeared. First messages of this log starts just after server reboot. 6.222.18 LEN=44 ...
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Privoxy - Annoying Error Used IPTables

I'm running privoxy off a machine that also has hostapd installed, I am trying to run all http traffic from hostapd through privoxy i have already tried this: iptables -t nat -A PREROUTING -p tcp ...
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120 views

ip rule not acting on fwmark

I'm trying to use iptables to load balance web traffic over multiple DSL lines by marking the packets and routing based on the mark. I'm working with CentOS 6.6, Kernel 2.6.32-504.16.2.el6.x86_64, ...
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1answer
42 views

package from IP arrives at certain port => open portrange to IP for x seconds

I have been toiling with an issue on iptables: I am trying to make a portrange open to a specific IP for x seconds/minutes as a result of a single packet being sent to a specific port. Not exactly ...
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51 views

Why is traffic matching the public zone instead of the desired zone?

Trying to self-train on firewalld I set up apache and configured the zones as follows: [root@localhost ~]# firewall-cmd --get-active-zones work sources: 192.168.122.1 public interfaces: ens3 ...
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169 views

Routing traffic for specific user to specific interface

I have a Linux box with these interfaces: eth0 Link encap:Ethernet HWaddr 14:da:e9:ef:75:7d inet addr:176.9.85.182 Bcast:176.9.85.191 Mask:255.255.255.224 tun0 Link encap:UNSPEC ...
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424 views

restrict IP traffic between VLAN sub-interfaces

I have a router/firewall-PC with two VLAN sub-interfaces eth2.100 and eth2.200: I would like to allow communication between networks 192.168.100.0/24 and 192.168.300.0/24(PC3 network). In addition, ...
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77 views

Dropping packets before mangle POSTROUTING

In iptables on Linux 3.10, why do packets which have been DROPed by the FORWARD chain of the standard table still appear in the POSTROUTING chain of the mangle table? -- I'm trying to use the standard ...
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1answer
264 views

How to use both syn proxy and connlimit rules with iptables?

I want to write both syn proxy and connlimit rules. I want to send packets to syn proxy first because of performance issue. Here is rule sample. I use bridge interfaces but I dont think it is ...
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65 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 ...
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47 views

Strange cron behaviour

I have a script that reads a list of IPs from a file, compares with the existing ones in a chain, and adds recently added IPs in the file into that chain. Running the script manually (e.g., ./script) ...
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1answer
55 views

(S/D)NAT over NF hooks

Could someone help on explaining the advantage of iptables NAT over the netfilter hooks. Say suppose, instead of using NAT if we create custom kernel module to bind handler with netfilter for PRE/POST ...
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1answer
33 views

Make a request through vpn interface

I want to be able to make request through a specific network interface, like this: ping -I eth0.1 google.be ping -I eth0.2 google.be This example works on my multihomed OpenWRT router. I now want ...
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46 views

VPN tunnel to two services on two servers?

I've got 2 CentOS 6.5 servers, each running one service: server A: 10.140.54.1/27 running service MySQL port 3306 server B: 10.140.54.2/27 running service httpd port 443 Server B's httpd service ...
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305 views

how to open up socks/SSH on different network interfaces?

iptables -A PREROUTING -i usb0 -t mangle -p tcp --dport 8080 -j MARK --set-mark 1 iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain ...
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369 views

Forward multicast between two LAN segments (Chromecast)

I've found some rules but most are inconclusive. Chromecast uses DIAL and discovers via multicast from what I've understood.. I have an Ethernet-connected computer which I would like to route via my ...
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801 views

How do I route bittorrent through a second interface?

I've managed to configure openvpn on my DD-WRT router such that the tunnel is up and working, but that it doesn't mess with routes at all (the default configuration wants all traffic to go through ...
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231 views

iptables rule to transfer UDP through a SSH tunnel

The problem I have two programs that runs on two distant computers and communicate through a specific protocol. All I know is that this protocol only communicates through UDP and uses the ports 1101 ...
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40 views

Extra overhead in MASQUERADE target

There's a part in iptables manual concerning SNAT and MASQUERADE targets. I know the key difference between the two, but I don't fully get the following sentence: It is still possible to use the ...
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50 views

How can I configure iptables for per application setup?

I am working on a project where we are building lots of micro-services. Each service is neatly packaged as an RPM. Ideally I'd like for us to have iptables enabled on all of our machines and it would ...
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97 views

Transparent Proxy

I am setting up attempting to set up a transparent proxy on CentOS using Squid. So far I have managed to filter the content and get it working perfectly. The only issue I am having is getting a form ...
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129 views

Defining IPv6 chains in ip6tables-restore/iptables-restore files, is it possible?

The format for the files generated by iptables-save/ip6tables-save and loadable through iptables-restore/ip6tables-restore stipulates that one can prepend -4 or -6 respectively so as to maintain the ...
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1answer
1k views

How does connlimit in iptables supposed to work?

I wanted to set a limit to the number of concurrent connections allowed on my web server. I tried the following rules on an iptables (v1.4.19.1) kernel 3.14.4-200.fc20.x86_64 with a default DROP ...
2
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1answer
73 views

iptables drop length and TTL condition doesn't work

With iptables utility on Linux host need to create mini firewall. I need to drop all incoming connections with package length greater than 722 AND TTL greater than 22. Need exactly AND. Drop only if ...
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1answer
685 views

Bad built-in chain name with iptables-restore

I saved my iptable settings on a Ubuntu 11.4 system using iptables-save >filename I then replaced the Ubuntu system with CentOS 6.5 and tried to restore iptables using iptables-restore ...
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760 views

Corosync & Pacemaker IPTables Rules

When using Corosync with two rings via multi-cast addresses 226.94.1.1 (Port 5405) & 226.94.1.2 (Port 5406) what iptables rules are required to allow two nodes to communicate optimally without ...