A firewall is a program that controls the incoming and outgoing network traffic on a system. Use this tag for all questions related to firewall configuration and operation.

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Installing pfSense firewall on an SSD

I was looking at creating a home firewall running pfSense (as I could not get IPCop to boot properly on my hardware). Doing a little research, however, I have some concerns with installing it onto an ...
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1answer
82 views

Dovecot/Postfix mail server replies to [SYN] with [RST, ACK] when user attempts to connect (POP3). Likely iptables?

Currently I'm trying to troubleshoot an e-mail server that will allow users to send e-mail, but not log in to the server (POP3) or receive e-mail using their Outlook clients. Previously this was ...
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1answer
1k views

Outgoing firewall application similar to Little Snitch for Mac

Is there a Linux application similar to Little Snitch? Little Snitch is an outgoing firewall that temporarily blocks outgoing network requests until the user decides whether to allow the connection or ...
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1answer
216 views

IPFW Port Forwarding

This is my situation: I want to connect to an OpenVPN server from my office (we're using a proxy, only ports 80 and 443 are allowed). Server IP address is: 176.31.250.232:843 My static IP address ...
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1answer
58 views

blocking all but specific ips from specific services in CentOS 7

In a CentOS 7 web server that needs to remain totally closed to the public, I need to block all ip addresses and then only allow specified ip addresses to access specified services. How can I ...
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iptables: using “conntrack” and “recent” modules to block unsolicited packets

When I only allow RELATED and ESTABLISHED packets, and DROP everything else, my firewall rules work perfectly and I have no problems: ### VARIANT A -A INPUT -i wlan0 -m conntrack --ctstate ...
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301 views

OpenVPN and routing problem on OpenWRT

My home topology: router1 (192.168.1.1) - D-Link dsl2540u server with static IP available from Internet (ADSL via ppoe). 4 LAN ports. router2 (192.168.1.2) - D-Link DIR-300 with OpenWRT. Plays ...
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0answers
99 views

Why doesn't ufw enforce firewall rules for traffic coming from Virtualbox VM

I've been running Linux Mint 17 on my laptop for a while and thought I had it locked down to not allow any incoming traffic through "Firewall Configuration" (ufw GUI)—I have also validated this from ...
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34 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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0answers
72 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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516 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 ...
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144 views

FreeBSD pf firewall, new connections severly delayed when nating

I have a newly setup fbsd 9.1 with pf, which itself doesn't experience any slowness when for example downloading a debian iso from my local debian repo (ftp.se.debian.org). Any machine behind it, ...
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0answers
762 views

openwrt firewall - block a set of ip addresses from internet access

I'm running OpenWRT Attitude Adjustment r33556 / LuCI Trunk (trunk+svn9325) on my WNDR3800. I would like to configure my firewall to: Only allow a specific range of IP addresses to access internet, ...
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263 views

Port Forwarding Between 2 Internet Machines

Here's my scenario: Setup There are 3 machines: A: on the internet : has ip (a.a.a.a), has port pa open B: my server / gateway : has ip (b.b.b.b), has port pb open C: on the internet : has ip ...
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0answers
841 views

pfsense long ping to google

I have a pfsense box set up. What happens is I set a rule so I can't hit the admin interface 192.168.3.1 from the box. With the rule enabled --- www.l.google.com ping statistics --- 2 packets ...
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51 views

How to setup reverse FTP in RHEL?

Researched: http://www.thecave.info/export-proxy-username-password-linux/ http://stackoverflow.com/questions/5334110/text-based-ftp-client-settings-behind-a-proxy ...
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25 views

firewall-cmd forward rules for interface with multiple ips

I'm looking for a way with firewall-cmd or another command to do the following. An incoming public interface has multiple ip addresses bound to it. How can I forward ports only for one of the ip ...
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53 views

Linux Bridge Network with Static IP Addresses and Firewall

any and all help is appreciated. I am trying to set up my Network Map Can you give me advice in setting up my interface file? If I set a static IP on my PLC on the same gateway, I shouldn't need to ...
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18 views

Initial iptable rule and knockd operation in vps

Today I launched a vps with Debian 7 x64 and started playing around with it. I installed xampp as well as knock daemon to get my hands dirty. So, all I wanted to do was to actually block all requests ...
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55 views

iptables: can't open tcp port

I'm running a Raspberry PI B+: Linux pi 3.12.28+ #709 PREEMPT Mon Sep 8 15:28:00 BST 2014 armv6l GNU/Linux The Raspberry is connect via lan (dhcp. ip: 192.168.78.29) to the local network. I'm trying ...
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114 views

Iptables and --tcp-flags

If I have the following rule in the nat-table in the prerouting chain: 0 0 REDIRECT tcp -- eth5 any anywhere anywhere tcp flags:FIN,SYN,RST,ACK/SYN redir ports ...
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Are there any loopholes in IP restricting sshd?

Say that i want to only allow username/password logins on my private network, but restrict all external sources on to key/cert login. I would do something like this: RSAAuthentication yes ...
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204 views

Configure firewalld for OpenVPN (server-bridge) in Fedora 20

I've installed an OpenVPN server on Fedora 20 (server-bridge), but I cannot get it to work. I'm almost sure that It's a firewall issue. I'm trying to connect from an OSX client, but I can connect ...
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2k views

Redhat / Centos 7 Firewalld best practice for pptp or L2TP/IPsec rules

Having a quick look at Centos 7, and though I'd spin up a VPN daemon or 3, but immediately discovered the usual packages aren't yet in the core repositories, so had to dig around and found the ...
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58 views

How to debug the network issue in case of blocked database connections

I am trying to understand if my analysis of the below information is correct. For all the 3 scenarios listed here, port 80, port 3306 and port 22 are open in the server's firewall. Also, for all the 3 ...
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99 views

How do I control ip routing in the new firewalld?

I have the following scenario: Our fedora server is connected to the internet on eth0 and has a second nic, wlan0 acting as an access point. The purpose of the access point is to provide a connection ...
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220 views

iptables server behind NAT accessible from outside as well as inside the nat

I have 2 machines with a KVM running on each machine - so two kvms with the below networking Host 1: 192.168.10.100 (eth2) 10.10.100.1 (virbr1) KVM 1 (NAT with Host 1): 10.10.100.128 (eth0 ...
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103 views

Linux firewall distro that can configure a vpn connection as a WAN interface?

I'd like to setup linux as a router w/firewall between My machine and the internet. The linux box should connect to a VPN account using OpenVPN on boot (managed to get that done). Then the firewall ...
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141 views

pfsense: No more processes

Sometimes my pfsense (1.2.3-RELEASE) goes crazy: every nat rules go down the web interface reply me with many errors (Warning: shell_exec(): Unable to execute...) my ssh daemon refuse to open a new ...
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545 views

iptables and physdev match confusion

I'd like to be able to prevent a network bridge from generating certain types of traffic from some of its interfaces. If I understand iptables correctly, packets generate by a device appear on the ...
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131 views

cntlm: the request was denied

I have configured CNTLM server between users and Windows TMG firewall. CNTLM configured with "allow all" - no any ACL or something like it: Gateway yes # # Useful in Gateway mode to allow/restrict ...
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37 views

How to send packets coming from a second router on a particular port back to the router, using iptables not a route

I have a Linux server which runs a particular service listening on a single TCP port. The Linux server connects to the internet using a PPP connection and also acts as router for a local network using ...
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53 views

Shorewall “ERROR: Ordinary users may not start the /etc/shorewall configuration” in Cygwin

I am using Cygwin on Windows 7 and I have installed Shorewall 4.5.21.5. When I try to start shorewall in Cygwin, it gives me error: $ shorewall start ERROR: Ordinary users may not start the ...
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311 views

destination IP mangle table

I have machine with 2 interfaces: eth1 connected to internet (ip xx.xx.xx.xx) eth0 connected to my laptop (ip yy.yy.yy.yy) I add those lines to the firewall file in order to manage the bandwidth ...
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159 views

Firewall config prevents hibernate connecting to postgres in CentOS6.3

I have an operating environment in CentOS 6.3 that has tomcat7 and postgres9.2 installed. There is just one web application deployed in tomcat that tries to establish a connection from localhost to ...
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181 views

Full network logging via linux firewall ( iptables )?

How truly enable full network logging via iptables? There is an option --log-prefix to add a tag to log entries. But the log entries don't show all complete packets. What a grand way to enable full ...
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87 views

how to list blocked connections events by the firewall?

So, I used firestarter that had logged blocked connections events with some useful details (but it is not being updated and I found somewhat unsafe as any moment we could click to deactivate the ...
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100 views

Firewalld SELinux

Is there any way to better explanation firewall-cmd than the one given in Fedora18 wiki. I am trying to convert iptables to FirewallD in cmd line without GUI but cannot find a decent example or ...
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143 views

Perform Cisco's DNS Doctoring on FreeBSD

How to perform a change in the DNS response from a DNS server to be a different IP address than the DNS server actually answered for a given name? ...
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0answers
143 views

What other rules should I use to allow PPTP outbound connection?

I already allowed outbound connection to TCP/UDP port number 1723, but PPTP connection still fail to establish, If I allow all outbound connection, the tunnel will just go fine.
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kernel security and IDS Firewall + AV together or not?

I try to hardening my server. For doing so, I got a general question: Should I install kernel security patches like selinux and an Anti-Virus with Intrusion Detection Firewall? Does it make sense to ...
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21 views

How to send all packets passing my firewall device to logging server?

I want to send all packets that pass my firewall device to logging server to inspect contents of passing packets on my logging server. It seems like my device doesn't support that feature explicitly ...
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0answers
45 views

how to make firewall changes permanent via firewall-cmd?

I am trying to open some ports in CentOS 7. I am able to open a port with the following command: firewall-cmd --direct --add-rule ipv4 filter IN_public_allow 0 -m tcp -p tcp --dport 7199 -j ACCEPT ...
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28 views

OpenVPN on Ubuntu VM

I am trying to create a VLAN Network from my home network for a web-dev platform. I am running Ubuntu servers in VirtualBox on a Windows 7 machine. I am running an Ubuntu DHCP/OpenVPN/Shorewall ...
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139 views

Network firewall on CentOS, host cannot be resolved?

I have a centos machine and I am trying install some dependencies using yum. When I do this I keep getting a message saying the host cannot be resolved. I was told the previous person that used the ...
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Port randomly closing (iptables)

I'm running CentOS 6.5 on a VPS and one of the services I have running is murmur/mumble (A voip application). The issue I'm having is that the port clients connect on will be open when I initially ...
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How to disable domain service at port 53 on WAN side in OpenWRT?

nmap on the WAN IP shows PORT STATE SERVICE 53/tcp open domain after basic configuration on a fresh OpenWRT (version Chaos Calmer) system. But the service should not be visible from WAN, but ...
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How can I use 0.0.0.0/0 in ipset hash:net,port?

Right now, if I do ipset a ansible_allowed 0.0.0.0/0,tcp:22 I get ipset v6.19: The value of the CIDR parameter of the IP address is invalid and instead I have to add 0.0.0.0/1,tcp:22 ...
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196 views

Unable to SSH into Puppy Linux, even though SSHD is running

I installed OpenSSH client and server on my Puppy Linux computer. That computer is behind a router. I tried to ssh into it over the internet (outside the router) but it times out. Also doesn't work if ...
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169 views

What is wrong with these iptables' rules?

The following is what I got after googling: iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT #allow loopback access iptables -A OUTPUT -d 255.255.255.255 -j ACCEPT #make sure you ...