iptables allow creation of rules to define packet filtering behavior.

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IPTABLES is slow after adding '-A INPUT -j DROP' to rule list

I am just getting started with iptables and stumbled across something I don't really understand. FYI, I followed the instructions of Ubuntu wiki's IptablesHowTo. The nat and mangle tables are empty, ...
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1answer
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Creating a NAT from loopback to a remote server

My goal is to redirect connections from the local host to a remote server, and be able to change the remote address on the fly, without any client config changes. I can do this now using a nat on the ...
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1answer
2k views

tc on bridge port

I have a 4 port bridge: root@Linux-Switch:~# brctl show bridge name bridge id STP enabled interfaces br0 8000.000024cd2cb0 no eth0 eth1 ...
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1answer
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Enable RTSP in iptables

I'd like to receive a RTSP stream via VLC, but when I try to run sudo -u non_root_user cvlc -vvv -I dummy rtsp://ip:port/x.sdp I get: Unable to determine our source address: This computer has an ...
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1answer
836 views

Is there a way to match an inet and inet6 IP set in a single rule?

Is it possible to have one IPv4 and one IPv6 IP set (ipset(8)) within the same rule? I have several rules that depend on one set of IPv4 addresses and another set of IPv6 addresses respectively, but ...
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1answer
567 views

Using source routing (LSRR) - any ideas?

What I want to do is conceptually very simple, but I can't find any information or help about how to go about doing this. Basically, I want to configure my networking to use source routing (LSRR). ...
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1answer
114 views

Simulate ethernet cable unplugged on a remote machine while staying connected

I am working from home on remote embedded Linux machine "X" via ssh. It has one physical network card. I need to simulate Ethernet cable unplugged condition on the same remote machine "X" , while ...
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dmesg flooded with firewall logs

In my iptables, I have a rule which logs dropped packets: -A INPUT -i eth0 -j LOG --log-prefix "FW: " --log-level 7 -A INPUT -i eth0 -j DROP And in /etc/rsyslog.conf, I have ...
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Undo iptables modification

I ran the following iptables commands to create a blacklist rule but used the wrong port: iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --set --name SSH iptables -A INPUT -p tcp -...
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Why isn't the Iptables persistent service saving my changes?

I followed this tutorial to set up IP rules on ubuntu 12.04. Everything worked fine on setup -- but now I've made changes to the firewall that do not persist upon reboot. I do not understand why that ...
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1answer
192 views

What is the IPv6 equivalent for 127.0.0.0/8

I am trying to set up an IP6tables firewall on Linux and I basically want to start copying my IPv4 configuration. One of my rules simply accepts all traffic to the localhost subnet: iptables -A ...
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487 views

Why do some TCP reset packets show up in my iptables log?

I started to add some basic iptables rules on my Debian Jessie server. My objective is to filter and log network traffic (for security and learning purposes). Disregarding ICMP packets, these are ...
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iptables multiple -d flags not allowed

I am trying to log all my outbound connections to a file using iptables. This is my rule: -A OUTPUT ! -o lo ! --destination 127.0.0.1 -m state --state NEW -j LOG --log-prefix "new_connection " --...
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How can I redirect ports 80 and 443 to 8080 and 8443 with iptables?

I'm looking at the documentation for a Tomcat 6 webapp called DSpace, specifically in regardds to running Running DSpace on Standard Ports (80 for http:// and 443 for https://) I am trying to use "...
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2answers
736 views

Why can I reach a different interface's IP address?

I'm wondering about this, and I can't seem to find an explanation on the internet. I have a linux gateway which has multiple interfaces: eth0: external ip eth1: 172.16.1.1/24 eth2: 172.16.2.1/24 ...
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1answer
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How does iptables recognize packet state?

Consider these two sets of rules: Set A -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -A INPUT -j REJECT -A OUTPUT -j ACCEPT Set B -A INPUT -m conntrack --ctstate ESTABLISHED,...
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1answer
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iptables: multiple exclusions on port forwarding

I have an existing iptables setup that does port forwarding. In this port forwarding scenario there are some instances where I do not want it to port forward. So, for instance I have this defined: ...
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769 views

Can iptables rules manipulate IP sets?

In iptables-extensions(8) the set module is described and it is discussed that it is possible to react to the presence or absence of an IP or more generally a match against an IP set. However, it ...
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How to Block SSH Brute Force via Iptables and How does it work?

I'm planning to add the following rules to iptables to stop ssh brute force attack which are common these days. -A INPUT -i eth0.103 -p tcp -m tcp --dport 4522 -m state --state NEW -m recent --set --...
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1answer
467 views

How to deny access to specific port when destination is NOT a specific host?

I'm trying to DENY access to port 1000 when it is being accessed through any host or IP that is NOT a specific host. I.e. If I try to access the service on sub.domain.com:1000 I should get in. If I ...
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2answers
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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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3answers
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Why must loopback traffic be authorized using iptables to get web access?

I thought the following was necessary was necessary for outgoing HTTP on a desktop (non-server): iptables -A INPUT -p tcp -m multiport --sports 80,443 -m conntrack --ctstate ESTABLISHED -j ACCEPT ...
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4answers
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Can't add large number of rules to iptables

I made a very simple bash script (echo at start, runs commands, echos at end) to add approx 7300 rules to iptables blocking much of China and Russia, however it gets through adding approximately 400 ...
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1answer
743 views

forward all mysql traffic to a ssh tunnel

I have a local application that needs to connect to a remote mysql server at 40.40.40.40:3306 The main firewall blocks all connections but ssh, I can set up a ssh tunnel and connect to the server ...
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1answer
650 views

Can iptables be used to monitor TCP timeouts/resets system-wide?

I'm trying to determine if an application's connection to a database is internal to the application or due to a networking event. This seems like something netfilter would have system-wide visibility ...
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1answer
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iptables: redirect local request with NAT

I'd like to redirect local requests to port which is translated with NAT. I have following rules: iptables -t nat -A PREROUTING -p tcp --dport 9020 -j DNAT --to 10.0.3.11:80 however request coming ...
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2answers
430 views

What tool to execute a command on repeated syslog entries?

Occasionally, one VPS under my control gets bombarded with POP3 login attempts. They all fail, but the huge number of spawned processes and active connections pretty much amount to a DoS attack. When ...
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2answers
249 views

Why were tables built into ipchains?

Why are tables built into ipchains? What was the benefit of adding tables to ipchains? Is there a simple scenario that would illustrate how tables are used to increase performance or offer some other ...
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1answer
62 views

Is it possible to reduce information in iptables log?

I noticed that there are data in the iptables log that I don't need, so I was wondering if it's possible to change some configuration so that the log has less information, thus reducing the log's size....
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2answers
388 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 ...
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2answers
795 views

Redirecting loopback traffic through a router

For some tests purposes, I am running multiple socket-based applications on one machine and want to simulate "real" network conditions between them. I thought the simplest would be to redirect all ...
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1answer
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Proper way to handle FTP over SSL with restrictive firewall rules?

Without SSL, FTP works fine over a stateful Firewall, like netfilter (iptables) + the nf_conntrack_ftp kernel module like this: # modprobe nf_conntrack_ftp # iptables -A INPUT -m conntrack --ctstate ...
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Restrict bandwidth with DD-WRT

I have DD-WRT installed on my router and I would like to be able to restrict the bandwidth both up and down on a certain IP or Mac address. I am happy to get my hands dirty and use console. I am sure ...
4
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1answer
99 views

Identifying source of audit messages in kern.log

I recently installed the auditd package on my Debian machine. I did some testing with auditctl, creating a single rule to watch a directory, proved something, and then removed and purged auditd. ...
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1answer
392 views

IPTables rules for specific processes [duplicate]

I have a lot more experience with the Windows Firewall with advanced functionality than I do with IPTables. With the WFAF, I was able to lock down a program so that it could only connect over specific ...
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2answers
143 views

Did this tutorial block pings to my server?

I am a programmer teaching myself linux admin stuff. I followed this tutorial to setup a firewall on a VPS. As a part of that tutorial, I block all traffic except for web traffic and SSH traffic. I ...
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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:~# ...
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Is it possible to set-up a VPN in such a way that I disconnect from the Internet if it goes down?

How can I set-up a VPN so I loose connection to the Internet if it goes down? I use Ubuntu and have used the network-dialog to use a VPN; but if the VPN goes down, it just switches to the non-VPN (...
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2answers
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Having Linux port remap to itself

I have a scenario: I have 4 server and 3 web inbound requests that I have to allow through a modem/router. the ports are https(ssl)443 ssh22 and http80. All 4 servers want them. I had set up the ...
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1answer
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Force VPN using IPtables?

I want to force the use of VPN using iptables, therefore while VPN is disabled no outgoing traffic shall be allowed (except maybe some DHCP stuff...). Now i guess I could just block everything not ...
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3answers
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IPTables and transparent proxies

I have set up a local, transparent TCP proxy on localhost. I want to redirect ALL TCP traffic to this proxy, so it can handle it and nothing "leaks out," circumventing the proxy. I need to use ...
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1answer
89 views

How to redirect web traffic to specific host with iptables

I want to be able to redirect a host in my Lan to an specific ip address and port. I can achieve one thing which is that only my desired host can access the ip address, but I can't get the user to ...
4
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1answer
173 views

Using tc for traffic quotas?

Is it possible to implement traffic quotas (absolute limits, not rate limits) based on the network classifier cgroup? I see there is the iptables netfilter 'quota' extension, which seems to do ...
4
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1answer
363 views

Debian Wheezy subnet configuration (proxy, MASQUARADing etc.)

I have a "server" with eth1 having a full IP address, DNS, gateway and proxy name connected to the university internet/intranet provider and eth0 IP 192.168.1.2 connected by a gigabit switch with two ...
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2answers
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How can I prevent iptables from counting bytes and packets on empty chains?

Background I occasionally have firewall rules that I need to use for maintenance windows, but don't want active (and therefore consuming CPU cycles or slowing the network interface) the rest of the ...
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1answer
438 views

How do you do NAT port redirection with PF?

In Linux, you can do NAT port redirection with a command like this: iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 8000 What is the equivalent with BSD's PF?
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fail2ban log parsing too slow on Raspberry Pi - options?

I'm running fail2ban on a Raspberry Pi at 950MHz which I cannot overclock further. The Pi is occasionally subject to SYN floods on particular ports. I've set up iptables to throttle the rate of SYNs ...
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iptables port forwarding

I have a CentOS server with Java/J2EE(Tomcat) installed on TCP port 8080. I have two interfaces, eth0 and lo. I need to forward all incoming connection on TCP port 80 to 8080. I tried doing the ...
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1answer
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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 ...
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1answer
169 views

iptables change log

Somehow an iptables rule was added to one of my systems. Does (or can) iptables keep a log about when and (maybe) who made a rule change? If iptables itself can't, is there a wrapper that might do ...