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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How to drop IP packets received on the default route interface when no other than default route is found?

I am setting up a router based on a linux kernel. As expected, ipv4 packets received on the interface used by default route are sent back to the same interface in case no other route is found. Is ...
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2k views

Iptables drop forward packets to specific host

I am having trouble isolating a specific host from others on my lan. What I am trying to do is only allow communication between 192.168.0.2. and 192.168.0.8 as well as not allow any other host to ...
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134 views

Can iptables be used to convert a single-homed host into a NAT server?

I have an Internet-enabled machine, HostA, with one NIC. I have another machine, HostB, with one NIC that is not Internet-enabled. I would like HostB to be able to share HostA's Internet-connection. ...
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108 views

Linux gateway / DNAT: restrict to certain interfaces

I have various machines with a number of network interfaces: eth0: a local LAN eth1: sometimes used for the connection to the Internet gateway ppp0: Modem uplink as an alternative to eth1 tun0: ...
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2answers
35 views

Problems in creating rules in iptable

Hello to all :) I need a little help with creating a rules. Im starting to learn iptables and firewalls but I have some questions. I need to allow HTTP communication only from PcA to PcB./ My code is: ...
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933 views

How does iptables masquerading allow to access a different local subnet?

My Linksys router (IP 192.168.1.1 inside a /24 subnet) is connected to my ADSL modem (IP 10.0.0.138 inside a /24 subnet) to establish an internet connection via PPPoE. To be able to access the modem's ...
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672 views

How to allow access to only specific IPs with Parallels VZ built-in firewall?

How can I use Parallels Virtuozzo's built-in firewall utility (called psa-firewall under the hood apparently actually psa-firewall seems to be a seperate Plesk interface - either way, it's basically a ...
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335 views

Iptables: Allow Internal LAN to access INTERNET

I have an internal network behind my router on eth0, and I have my router connected to the internet thorugh wlan0. I can't access the internet from inside the lan, how can I fix this? wlan0: ...
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UDP packet and firewall

I notice when I send udp packets from computer A to computer B, B can receive the upd packets correctly but if I send udp packets from computer B to computer A the udp packets are not received A and ...
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186 views

IPTables masquerading stops working

In a classical SOHO setup I am running a Debian box as router/firewall. For an unknown time now I have an issue, where the MASQUERADING on the output connection (PPPoE) stops working for one of the ...
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412 views

Iptables: allow specific ips on specific port

I am trying to allow a few IPs on port 80 and disallow all other from access port 80. Can someone suggest the iptables rules needed for this to occur?
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2k views

DNS resolving broken after installation of bind due to iptables

I successfully configured my web server (Apache, PHP etc.) and blocked the ports I don't need using iptables, which was working perfectly fine. Today, I installed BIND and configured it, which also ...
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531 views

Port 6667 can't be reached outside of localhost

I've got IRCD-Hybrid installed with the following listen config: /* listen {}: contain information about the ports ircd listens on (OLD P:) */ listen { /* port: the specific port to listen ...
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657 views

how to telnet redirect ip and host using iptables

I try to telnet from PC 3 To PC 1 and it's redirect to PC 2 PC 1 : 192.168.0.1 PC 2 : 192.168.0.2 PC 3 : 192.168.0.3 i have command like this in PC 1: iptables -t nat -A PREROUTING -p tcp -d ...
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181 views

1:1 NAT IP address using iptables

Suppose I have 2 internal networks: 1.1.1.0/24 and 1.1.2.0/24 I would like to NAT a specific IP address from one network to the other, in which the new address would be obtained via DHCP. For ...
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273 views

CSF Unresolved issue

I began receiving service failures for CSF/LFD once the limit was reached in iptables preventing the service from working properly. I flushed all iptables rules, and redid by rules using CIDR rather ...
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124 views

iptables rule cannot be added

Is there anything wrong with these rules? They cannot be added to iptables, no error but they just don't show up in iptables -vnL iptables -I FORWARD 1 -s 1.2.3.4 -p udp -m connlimit ...
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940 views

Iptables - having trouble opening port 443

I am attempting to set up https, but I am having difficulty opening that port. Nmap scan report for localhost (127.0.0.1) Host is up (0.000073s latency). PORT STATE SERVICE 443/tcp closed https ...
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503 views

Router 2wire, Slackware desktop in DMZ mode, iptables policy aginst ping, but still pingable

I'm in DMZ mode, so I'm firewalling myself, stealthy all ok, but I get faulty test results from Shields Up that there are pings. Yesterday I couldn't make a connection to game servers work, because ...
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911 views

DHCP Client Can't Find DHCP Server

I currently have 3 machines: CentOS (router) eth1 - 18.0.168.1 eth2 - 145.165.34.1 Windows Server 2008 (server) 18.0.168.2 DHCP scope - 145.165.34.10 - 145.165.34.20 Windows 7 (client) Supposed ...
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424 views

How to setup IPtables to allow capture network traffic from a virtualbox VM configured with NAT

I would like to have a VirtualBox virtual machine that can't get online. I want to be able to monitor all network traffic attempts from the Linux host. So, if the virtual machine attempts to make a ...
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207 views

Using my previous desktop computer as custom ubuntu router, will throughput be high?

I'm going to be redoing my home network soon and am thinking of using a dedicated ubuntu machine to use as the router/firewall as well as being a web server, nas (media file server), dns, wifi, and ...
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73 views

Regulate outgoing ip traffic on a VM

I am making a virtual network setup for my high school cybersecurity team to practice. I am connecting all the VMs together through a VPN and then people who are practicing will VPN in and ssh/remote ...
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122 views

Mark packets across computers?

I use Transmission on Ubuntu and I'm having this issue, which basically says that QoS is broken because there is no way to limit which outgoing ports uses. I was thinking of doing a dirty and ugly ...
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488 views

filtering Internet traffic and caching on another machine using a dd-wrt router

In my home network, I have a spare machine which I would like to configure to filter Internet traffic (block ads) as well as cache content. I would like to tell my DD-WRT router to pass all Internet ...
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881 views

How to drop traffic before it hits existing iptables conntrack rule?

I am running an application that injects iptables connection tracking rules into the kernel so the machine can forward incoming UDP traffic to its destination as fast as possible. Some of the ...
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84 views

Chaining subnet fails

Is it possible to do the following: Machine1 Kubuntu 8.04 desktop wired internet Cable modem Machine2 eepc701 Xubuntu 1O.04 wired machine1 cross ethernet cable Machine3 nokia n900 wireless to ...
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791 views

iptables + vpnc + Cisco IP Phone 7941

I have a Linux gateway with kernel 2.6.39 connected to a Cisco ASA 5500 with vpnc. I'm using iptables with masquerading and forwarding to give the LAN access to the tun0 device connected to the VPN. ...
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iptables ACCEPT policy

In Redhat EL 6, iptables INPUT policy is ACCEPT but INPUT chain has REJECT entry in the end. /etc/syconfig/iptables is as below: *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] ...
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3k views

iptables openvpn forward selectively from eth to tun

Simple for those who know, indecipherable for those who don't... I'm running openVPN on (hypothetical) 66.66.66.66, I want to FORWARD incoming traffic, arriving on interface eth0 to interface tun0. ...
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588 views

Removing/Disabling Firewall on Linux CentOs seem to happen temporarily

I tried following the instructions in this link to disable and remove iptables firewall using commands: # service iptables save # service iptables stop # chkconfig iptables off # iptables -F # ...
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452 views

Firewalling all incoming traffic with custom rules

How do you automatically block all incoming traffic by creating custom rule for every connection (in real time) using iptables? To clarify - the situation is that my linux box is being DDOSed via ...
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402 views

Linux box acting as wireless access point to share the internet connection

A linux machine is connected to internet over two interfaces ppp0 and ppp1 using two modems. Also this machine acts as wireless access point through an interface say, eth0 with ip address 192.168.1.1 ...
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623 views

Quotas with iptables

pkts bytes target prot opt in out source destination 12770 2385K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 quota: 2000000 bytes 0 ...
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666 views

Ubuntu 9.04, Firestarter complaints even behind the NAT router

I'm behind a router. In router config, I blocked: all (inbound and outbound) UDP inbound ICMP Local iptables are configures with Firestarter wizard: block all incoming connections allow all ...
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93 views

Network problems that might be related to NAT

I have an odd setup where there is a router(Router 2) routing between network network 1 and network 2. One router(Router 1) with nat for internet access that routes between internet and network 1. ...
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438 views

Create iptables rules

I want to make the following rules in iptables: Open port 80, 5432 and 22 to all IP addresses Open port 27017 only to these IP addresses x.x.x.0/24 In all the cases I want both tcp and udp ...
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153 views

no websites loading using iptables nat

I'm using a 3G modem whilst o2 tranfer over adsl. trouble is no websites load but I can resolve domains. I enabled masquerade on the PPP0 ( modem) interface. added the server as default route for all ...
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248 views

Fedora iptables error

I recently installed Fedora 13 and receive this Boot message: iptables: Applying firewall rules: iptables-restore: line 14 failed I am new to Linux and need help in figuring out how to fix ...
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950 views

iptables and NetworkManager on Ubuntu

I want to use iptables configuration on my Ubuntu 10.0.4 desktop, however I read that Network Manager and iptables have some conflicts. Should I uninstall NetworkManager? If yes, how? ...
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3answers
113 views

how do i set up this firewall?

i use fedora 13, and i have firewall turned off now. but i want to allow all incoming connections and outgoing connections except to a port P. i want to allow connection to port P only from certain ...
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332 views

how do I forward *only* http proxy across vlans?

My router has two bridges, br0 and br1. I'm sharing wifi access, and the guest subnet will be 192.168.2.x. The home subnet will be 192.168.1.x. I want all traffic destined for port 80 from the ...
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2answers
247 views

How to set iptables?

I want to allow traffic only for httpd(nginx), port 2710 and ssh. I've tried the following, but it didn't work and apparently all httpd, traffic was blocked and I couldn't access ssh as well. There ...
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1answer
867 views

Iptables prerouting and IP forwarding

I have a linux machine used as gateway for a Win XP machine. Both are in Virtual machine for testing purpose. Now I want to trick the Win XP user (me) with the forwarding of an IP address: I want to ...
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Iptables: allow wget

for some reason the following rules block wget. iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp --dport 80 -j ACCEPT iptables -A INPUT -p tcp ...
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IpTables: rule to allowing outgoing traffic

I need rule to allowing outgoing traffic from intranet addresses 192.168.X.X to foreign addresses 123.123.123.0-63 and by using tcp Protocol. Sorry for bad english Thanks
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270 views

Bind incoming packets to 1 interface and outgoing packets to 2nd interface?

I am have a Linux machine with 2 network interface cards, I need to use one for incoming packets, other for outgoing packets.
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144 views

Configure IPTables [duplicate]

We have RHEL 5.0 squid proxy in our office. Our LAN is 172.20.12.0 /24 n/w. Proxy ip is 172.20.12.4 /24 . I want to share Internet through proxy. Most importantly: Suppose I have flushed the ...
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697 views

LInux squid proxy

We have RHEL 5.0 squid proxy in our office. Our LAN is 172.20.12.0 /24 n/w. proxy ip is 172.20.12.4 /24 . I want to share internet through proxy. Most importantly: I want to give full access to ...
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1answer
174 views

DD-WRT Wifidog - Redirect isn't working

I have flashed a ASUS AC-RT56U router with DD-WRT version V24-preSP 2201412-22-2014-r25697. Now I want to make it into a hotspot with wifidog TO PLACE IN A SMALL BUSINESS (FITNESS CENTRE) I have ...