Networking :: Preventing Internal Network Traffic With Firewall
Jul 3, 2010
Does anyone know if it is possible to filter/block network traffic between internal hosts on a lan?
Eg. : Linux firewall/router ( 192.168.0.1) - LAN Default G/W - all internal > external traffic gets filtered.
How would you filter tcp/ICMP/UDP traffic from internal host a ( 192.168.0.2 ) to host b ( 192.168.0.3)
All the internal hosts have the linux f/w as the default gateway, and are all on the same /24 subnet.
I would like to know if I can filter traffic between internal hosts.
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Jul 28, 2010
I have just installed CentOS and it is working fine!I made a masquerade with the document there: I didn't used the script, because right now, I do not completely understand it, and obviously I am not modifying anything by leaving it like that.I was using Mandriva before and I am used to graphical tools My questions are:I add the following lines in my iptables:
[root@localhost ~]# service iptables stop
[root@localhost ~]# iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
[root@localhost ~]# service iptables save
[code]....
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Sep 29, 2010
I need to set up my centOS computer as a firewall in my home network. Ive got 2 interfaces, eth0 and eth1. I want to allow and forward all traffic on eth0 and block all traffic on eth1 except ssh, ping(icmp) and DNS. How do I do this? Ive tried some editing in /etc/sysconfig/iptables but no luck.
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Jan 4, 2010
I have Ubuntu 8.04 as virtual host. On this host I have installed VirtualBox virtualization software. I have installed Windows XP as virtual machine and installed HTTP server.I would like temporally disable all network connections to host and virtual machine.So on Ubuntu host I have set firewall settings:
Code:
sudo iptables -F (to flush - delete all firewall settings)
sudo iptables -P INPUT DROP (to disable all input traffic)
[code]....
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Jun 10, 2009
I am looking for a solution for our LAN traffic monitoring and would like to use some opensource linux application. I have a linux box with two NIC cards and what I thought is the following: Our setup is as follows. Internet comes in through the router and into the firewall. From the firewall it goes into our switch and distributed among the workstations.
I have no access to the router or the firewall as they are centrally configured. I would like to place a device into the loop through which I could monitor the LAN traffic.
Can I put a linux box between the firewall and the switch and have all packets going through registered and logged? I have a proxy server (non transparent) and that captures some but not all. I would like to get all packets registered without interfering with the LAN etc.
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Feb 16, 2010
I have a DELL running CentOS 5.4 with 2 active NICs, one with an external IP address (eth0) on 123.456.78.9 and another that is connected to our internal network (eth1), 192.168.2.x. When I reboot the server, everything works glowingly. External traffic is correctly routed over the external interface (eth0) and internal traffic over the internal interface (eth1). After some random amount of time, a couple of hours and sometimes a couple of days, all traffic starts getting routed over our internal network, so DNS requests fail, internet pages don't load, smtp connections fail, etc.
I'm assuming that everything that's not headed for our .1, .2 or VPN internal networks would go out the external interface. And why this works for a period of time and then stops working is beyond me. And when external traffic starts going over the internal interface, I just reboot and it starts working like it's supposed to again.
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May 2, 2010
I have a ubuntu computer set up as bridge between gateway and lan, with the lan connected to eth0 and gateway on eth1.
I'm trying to get it to basically block everything incoming except for the ports i specify, but also allow outgoing traffic. I've found, tried, modified som examples i found on the web, but still it wont block incoming traffic (ie, im still able to reach my webserver)
These are the rules, and i can't figure out why it wont block:
Code:
#!/bin/bash
iptables -F
iptables -X
iptables -I INPUT -i eth1 -j DROP
[Code].....
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Nov 21, 2010
My Ubuntu Box has 3 interfaces. eth0 (Internal 192.168.1.0/24)eth1 (External ISP DHCP)eth2 (External ISP Static IP)I need the outgoing traffic to internet for 1 of the internal pc (192.168.1.10) to only go only go through eth2
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May 13, 2010
I could no handle/circumvent on the past week, despite of the several "googling" and documents reading. I will try to mention all needed bits... I'm managing a network with the following structure:
eth0: internal net
eth1: DMZ
eth2: 10 mbit/sec sync line with eight public /29 IP's + a /30 interconnection network. All public IP's must use the interconnection's network gateway.
eth3: ADSL with ppoe with fixed IP (ppp0).
Now, a few extra info:
- All internal traffic is routed through ppp0 except when it's destined for DMZ and public IP's range.
- DMZ traffic is routed either through ppp0 or eth2. This is done by source IP.
- eth2 has on IP from the interconnection network, and six public IP's are also defined on eth2. Command: "ip addr add ...."
[code].....
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Sep 4, 2009
I wanted to know if i can install mrtg on a client computer in network and measure the network's router traffic.i know that it can be installed on the server.
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Feb 8, 2010
i have a linux server runnig oracle applications. i need to access this server from putty using ssh through internet. i did by registering my static ip with the dnydns.org and i am able to connect to the server. but now there is no security to authenticate any user as any one knowing the password can login to it.
i thought of configuring the firewall of linux server but the client ip`s are not static and they change continiously. so thought of keeping one more pc between the server and the router which will do the work of authenticating. but i am confuse as how to configure it to allow the packets coming from the internet after authenticating and to by pass the packets generated from internal LAN?
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Jul 29, 2009
I have a (virtual) server with 3 NIC's: 1 external (inet), 1 local and 1 DMZ. This server is my gateway.
I would like my internal network, where every server has a static 192.168.0.x IP, to access the internet via the gateway.
That means the traffic has to pass from the 'local' NIC to the 'external' NIC, connected to the internet.
Which setting do I change to accomplish this ?
Please check the sceenshot (attachment) for my current setup
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Aug 8, 2010
I get all my traffic from my router, as this computer seldom moves. So is there a use for a firewall?I am not sure, because when I scan my IP address with nmap, no matter what the changes I make in the firewall, it is always the same scan...cannot fingerprint OS...and all closed ports.The all closed ports thing only changes when i torrent, then i get a wide open port.
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Jan 16, 2011
I noticed a huge data transfer to my computer. I wasn't downloading anything big, I have just opened Firefox, Thunderbird etc. It stopped after a minute but I'd like to know, what that was - this wasn't the first time something like this happened. I promptly started Wireshark and captured a few packets, all of them look like this:
[code]...
I tried to look at [URL]... but that webpage does not work. what the traffic might be caused by? Couldn't anyone hacked my pc?
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Jan 20, 2011
Is there an easy way to monitor network traffic? I want to make sure my kids are surfing safe...
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Jan 31, 2010
I need software that measure the QoS of network traffic , Any recommend program?
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Feb 8, 2010
I am manually capturing and injecting Ethernet traffic (using lib_net/lib_pcap libraries) for an application. At the moment , both capturing and injecting are done on the same physical interface (e.g. eth0). The problem is that all the traffic that I inject, are captured again by my application causing an unwanted feedback of injected traffic. This caused that I had to implement traffic filtering when capturing traffic, which is consuming resources and eventually will become too complicated to support.
I have tried using virtual interfaces to separate the capturing and injecting streams, but that also presented the same problem as all the traffic from eth0 is forwarded to both eth0:1 and eth0:2. If possible I would like both streams to go through 1 physical device, using more PDs will be the last resort. I am also looking at using TUN/TAP devices to try and separate the two streams, maybe writing a user-space program that lies between the physical device and the TUN/TAP devices to do the routing of traffic.
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Jan 31, 2010
I need software that measure the QoS of network traffic , Any recommend program??
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Dec 8, 2008
Via a network traffic monitoring tool I see that my laptop is generating lots of outgoing (EDIT : incoming !!) network traffic. Although no download program is running or any other program of which I know that could be generating this much traffic. Something strange is going on and I need to know how I can find out which program( s ) are generating network traffic.
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Oct 18, 2009
how to configure my network for web traffic.Here is my setup:I have the following virtual machines, (all guest are running on CentOS 5.3);
firewall: Smoothwall 3.0, (hardware, not virtual)
guest # 1: Apache http server
guest # 2: Qmail server
guest # 3: Proftp server
I want all of these services on different machines for security reasons, (mainly the ftp server) how do I route the traffic from the firewall to the different machines? I have been looking at setting up a reverse proxy, however, everything that I have read says that a reverse proxy will not handle the smtp/pop3 traffic. Can I just use a DNS server to route the traffic?
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Aug 24, 2010
I wish to prevent some programs from "phoning home", and to allow other programs to access only specific web servers.Is there any way to interactively allow or decline outbound communication from individual programs on Ubuntu?
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Jun 4, 2010
I greet you at the same time ask me to help with a problem I have and I could not solve. Within the requirements I have is to connect a network that is connected by VPN to my LAN.The detail is I could have connection to the network by adding a network card (eth3) on the firewall and connect to the VPN router (DLINK) cable network, but I can not reach the other estin that are in the VPN.
It should be noted if I add a station within the network: 10.30.1.X/24 has no problems connecting with the other destinations.Physically this router is inside my 10.30.1.X DATA CENTER another wan.
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Oct 6, 2009
I am not too knowledgeable on networks, however I think this should be possible.I have a computer at work, which is connected to the work network. I have files stored on the central server here and also my local computer.
At this place, computer support say "We do not offer this service". However they also say "The simplest way to do what you are asking is to install an ssh server on your actual workstation".I have done this, and it the openssh server is working because I can test from my workstation by doing ssh user@hostname and it works.What I want to do however, is to connect from outside the network. Firstly, is this possible, and secondly, what is the syntax for ssh in order to do it.
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Sep 27, 2010
what I want to achieve is just to be able to say to who ever is killing our relatively fast connect that they aren't the only person using the network. Everyone just says "I hardly download anything." which is obviously untruthful as normally I can download at 1.5 MB/s but now loading even google.com takes way too long (same with pinging and all other sites). Once I do this, I can determine whether or not I need to call my ISP and do the long 'on hold' dance and "have you tried rebooting the router" BS.
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Apr 4, 2011
I am running Ubuntu 10.10, upgraded a few weeks ago from 10.04. I noted from the system monitor that the system was generating a lot of network traffic, on the order of 10Mbps if the information is correct (using system monitor and iftop). From the process table, it appears that smbd is accumulating a lot of CPU time, which sort of makes sense as I use Samba for printing from a Windows 7 laptop. But the traffic seems to be making a round trip as I just rebooted the system and it reports in about 10 minutes of uptime 1.2GB was send and 1.2GB was received. Laptop is used for work, it is sitting idle for the last 30 minutes (VPN connection, etc); no backup or other interaction with the Ubuntu system.
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Dec 28, 2010
How could I configure Ubuntu to be setup as follows...
Wireless Client ----> Wireless Router ----> Home Server ----> Internet
What is needed to make all of the wireless traffic go to my internet connection port. I will be having two ethernet cables plugged into the system one from the wireless router and one to my internet router.
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Aug 9, 2010
In my "computer room" I have an ATT U-Verse TV decoder box and my computer connected to a Netgear Switch. The third port on the switch connects to the ATT router. I've just noticed that when I power on the U-Verse TV box I start getting a lot (200-250 KiB/s) of received packets on my Debian Lenny machine as shown in the System Monitor app. I don't show any outgoing traffic in response. That explains why the lights on the switch are blinking at the same rate for both devices. So, what, if anything, is this telling me? Is this normal, or is the ATT router spamming my Linux machine for some reason? Is this a potential problem?
Added: Or is this just telling me that the NetGear FS-105 is not actually an ethernet switch?
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Jan 29, 2010
I have a server on my router on the DMZ. All outside traffic goes to it. This server has Apache running and the domain mysite.com resolves to the the DMZ web server. I have a second server on the LAN that also has apache running. I want to set up another domain, myothersite.com to resolve to the second server on the LAN. Since the main server is on DMZ I have the DNS A records for myothersite.com pointing to the public IP that the DMZ is on.
How do I get myothersite.com to resolve to the second webserver on the LAN? What configuration do I need to do on my DMZ server so it routes traffic for myothersite.com to the other server on teh LAN? Do I use BIND DNS? If so please advise on how to set that up. BIND DNS seems confusing and I having trouble knowing how to configuring it. Is there another option besides BIND?
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Apr 3, 2011
I have installed the graphic user interface for IPtables and enabled this firewall. However, I find it a bit strange. What is the difference between rejecting and denying the traffic? If I want to configure IPtables as two-way, how can I define which of my apps can connect to the internet and which can't? If this firewall is enabled, does it really run in the background, protecting the user,or does it run only when its GUI is opened?
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Mar 25, 2011
I suspect this is an initial configuration bug. All firewall logs seem to be going to all
three files. That causes a lot of clutter in the log files, and makes it difficult to see whether there are any serious problems being logged.
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