Security :: Can't Zero Out Counters In Iptables

Feb 25, 2010

I have a problem with iptables, when I execute


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OpenSUSE Network :: Ifconfig Eth0 RX Dropped Counters Since 11.4

Jun 1, 2011

I have been noticing a trend on boxes running 11.4 getting RX dropped packets where prior to 11.4 they did not get them. Basically every box running 11.4 now logs dropped RX packets. Have tried changing cables, and in one case replaced the NIC with a different brand (and driver) nic. Also played with receive buffers and yet the counters still increment. In addition to OpenSUSE, I run several operating systems to include Centos, Scientific Linux, Debian, OpenIndiana, HP-UX, VMS and so forth. So far this anomaly has only shown up on machines running OpenSUSE 11.4. Any one else noticing this on your OS 11.4 machines? If so, were you able to resolve?


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Software :: Clearing /Proc/Interrupts Counters Without Rebooting System

Dec 7, 2010

I have a question regarding the /proc/interrupts file. Let's say for example I had a server with 2xQuad-Core processors (so we have CPU0 to CPU7 ), and with 5 network interfaces. SMP affinity to all 5 interfaces was set to "ff", so all interfaces have done interrupts on all the processors. he network interfaces interrupts counters should look like this:

24: 32650776 32670506 50315017 32677739 32672119 32677935 32656299 32667496 IO-APIC-fasteoi eth2
27: 35233448 35285546 35317201 52657622 35315835 35339998 35221092 35246597 IO-APIC-fasteoi eth3
55: 37573056 35870363 35874607 35858010 37728061 35880275 35882340 35882127 PCI-MSI-edge eth1
56: 35861392 35863516 35865123 35865342 35864604 40515822 35861250 35863585 PCI-MSI-edge eth0
58: 30173318 30109146 30002990 30016870 30084937 30034759 46517278 30139103 PCI-MSI-edge eth4

Now let's say I've set the affinity to each of the network interfaces, so that it balances one per processor, so we have 5 processors working only for the network interfaces each processor with it's own eth. Now let's assume that the network interfaces generate very few interrupts, and that they show up every 5-6 seconds, so watching cat /proc/interrupts doesn't exactly underline the modifications unless you look with a ruler. Is there a way to reset the counters on /proc/interrupts so that they all start at 0, without rebooting the system?

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Server :: Cygwin Scp File Copy Counters Stop Increment / Decrement

May 31, 2011

I'm running cygwin 1.7.7 on a win2k3R2 Standard edition server. I have a RHEL 4.7 linux host I'm scp'ing files from to the windows system using a simple cygwin scp command from what appears to be OpenSSH_5.5p1 on the cygwin host. When I run the simple scp command on the cygwin host, the counters initially display and increment/decrement, albeit what is at a much slower rate than is actually taking place. After the percent complete reaches a little less than 10%, all the counters from the cygwin console window cease to increment/decrement.

However, when I cd to the directory on the cygwin host where the file is being scp'ed to, the file is continuing to be transferred and a much higher rate than the counters seem to show. Finally, when the file transfer is complete by directly seeing the byte count as equal between the hosts, the scp counters will suddenly jump to 100% complete. This is not the case with my linux to linux scp's. The counters increment/decrement as expected and transfers are about what I'd expect over the same network infrastructure. This appears to be a cygwin ssh/scp implementation issue. I've posited this question to cygwin with no response as yet. The only reference I've been able to find on the 'net refers to buffering causing file transfers to appear to complete later than the transfer really does..........

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Fedora Security :: Allow DNS In Iptables

Feb 1, 2009

I have been struggling with this for a very long time now. I have installed Fedora Core 9 on my computer. I have set it up as a caching-nameserver and this is working.

Then I wanted to secure my server with iptables, and I have so far made this script:

# Load the connection tracker kernel module
modprobe ip_conntrack
iptables -F
iptables -P INPUT DROP
iptables -P FORWARD DROP


I can reach the dns server with ping. When trying Nslookup it says that it got SERVFAIL from trying next server, and then it times out.

My resolv.conf file lists:

nameserver DNS-server

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Fedora Security :: Can't Get FTP Through Iptables

Dec 14, 2009

Im pulling my hair out trying to get ftp to work through iptables.Im using vsftpd

Table: filter
Chain INPUT (policy DROP)
num target prot opt source destination
1 ACCEPT all --


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Security :: Configure IPtables To Only Allow VNC Over SSH

Apr 4, 2010

I am trying to figure out how I can configure IPtables to only allow VNC traffic to an internal server over SSH.

My configuration is WAN < --- > Gateway (Ubuntu 9.10 Server) < --- > Internal Server (that I want to control with VNC over SSH)

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Security :: How To Keep Safe PC Using Iptables

Dec 5, 2010

I am using Fedora on my desktop pc. I want to know how can i protact my PC from outside world. What firewall policy should i implement in iptables to keep it more secure.

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Security :: Incorporate Into Iptables

Jan 5, 2010

I'm following an openvpn installtion how to and it says to add this to the iptables:

# External Interface for VPN
# VPN Interface
### OpenVPN

Any thoughts as the whole formatting is separate and has the addition of FORWARD rules, etc. I need the VPN running on the .199 address

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Security :: Iptables :everything Works Except Ftp

Jun 3, 2010

i set up a dmz to have a internet web server and ftp server, and ssh only from local network, so i wrote a iptables script to load during boot :


The problem is that everything works fine ( i have the same rules for other services such as samba, nfs, mysql on another server) BUT ftp there is no way to make it work. not even locally.when i try to connect, i log in, but while listing the directory i get MLSD ... and it hangs like this for a moment, then i get error message "connection time out" , "impossible to list directory". if i turn off the iptables script no problem,ftp works fine.. but why all services work and ftp no?

how do i have to modify the rules? what is strange also is that if i set as OUTPUT policy "accept", the server seems to be offline."host unknown" error message. I was thinking the rule INPUT is fine cause at least i can login, but the dir list is not going out, so gotta modify output rules. or state?

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Security :: IPTables - How To Set Default Allow

Mar 19, 2010

I've started a new job and have inherited a couple of RHEL4 64-bit servers. The firewall on them is currently disabled. I'm struggling to get them up and running as iptables is not the most user-friendly application. This lead me to downloading and trying a GUI front-end: Guarddog. Great app! But it doesn't have the default behavior I'm looking for. Here is what I need:

Default behavior: Firewall should be wide open, allowing ALL ports/IP's/TCP/UDP in and out of the server.
Blacklist: Oracle TCP port 1521 needs to be blocked in/out of the server.

This will help get us passed our company's security vulnerability scan. (We aren't able to patch/upgrade Oracle at this time because we'd lose vedor support with a legacy app). I will use these settings as a starting point, and then once I learn more and get more comfortable with iptables (or a GUI app) then I can fine tune things to make them more secure. As far as I know (correct me if I'm wrong) once I get a script I just copy it into /etc/rc.firewall and it will load when iptables starts.

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Security :: Iptables To Block Ip From Ftp?

Mar 6, 2010

Is this how I would do that?

iptables -A INPUT -p tcp --destination-port 21 -d ! -j DROP

This should block all incoming connections on port 21 from, correct? Thus preventing that IP from logging into my FTP.

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Fedora Security :: Iptables - Block Everything From Getting In My Pc

Mar 17, 2009

What i wanted to do was block everything from getting in my pc but still be able to surf the web and still use instant messenger.

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Ubuntu Security :: How To Reset The Iptables

Jan 14, 2010

i ran this


iptables -N rate-limit
iptables -A rate-limit -p tcp -m conntrack --ctstate NEW -m limit --limit 3/min --limit-burst 3 -j RETURN
iptables -A rate-limit -j DROP
iptables -I INPUT 1 -p tcp --dport 22 -j rate-limit

i am no longer able to ssh in to the machine , how can i reset iptables and firestarted back to default?

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Ubuntu Security :: Use Address Not Ip In Iptables?

Jul 24, 2010

i need to open this address, is there a way to use address not ip in iptables?

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Ubuntu Security :: Iptables Configured By UFW ?

Sep 17, 2010

I've recently moved from Firestarter to UFW/GUFW, and I wonder if someone could confirm if my iptables configuration is secure.

When I enter sudo iptables -L i get:


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Ubuntu Security :: Iptables Allow Via Spesific NIC?

Dec 29, 2010

eth1 has connection to the net via gateway ..eth0 on the same machine has users on a intranet and needs access to the internet, i need to allow internet connection and prevent packets which logically originate from the internet getting into the intranet

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Ubuntu Security :: How To Clear Iptables

Apr 21, 2011

Installing a router, and I need to completely "wipe" iptables (flush I mean) on both computers, and I think I run ufw/gufw on both, so that would need to be uninstalled. The router is very secure, has NAT, etc, etc, and I'd rather setup all that side of things in one point, rather than on each computer.

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Ubuntu Security :: Both Ufw And Iptables Running Together?

May 23, 2011

Can I have both ufw and iptables running together? My server is currently using ufw, if I add an iptables rule will it have any effect?

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Networking :: Configuring IPtables Security Of CPU

Mar 3, 2009

I new in Linux, I have a Centos5 since sunday and well I have to configure the iptables security of this cpu, I read a lot of examples of iptables in the internet and also another Thread from here but Really a don't know what to do, I saw lots of codes but first of all I don't know where I have to write that and my teacher don't want to help me in this homework. I tried to write the codes in applications --> accessories --> Terminal

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Security :: Setting Up IPTables For Kubuntu 10.4?

Feb 21, 2011

After discovering that the firewall was wide open I decided to finally study the iptables docs and learn how to add rules. Now, I've not yet finished reading guides and documentation but I'd like some advice before I set the default policy on the input chain to deny. I have added a permissive rule for the loopback adapter so that programs that use it do not become mute suddenly. I will also use netstat to see what ports to open for each program that connects to the internet. I'm not that interested in what ports to open but how to find what ports to open.

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Security :: Anyway To NOT Log Dropped Ports 137 / 138 In Iptables?

Mar 30, 2011

We do NOT support samba on our Unbuntu servers but still zillions of windows machines are constantly trying to connect on the SMB ports. I've added a rule that drops access to destination ports 137-138 and that seems to work. But it creates many many log entries documenting that the packet has been dropped. I've been researching and cannot come up with a way to suppress logging for these drops.

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Security :: Blocking Web Content With Iptables?

Aug 8, 2010

Is possible blocking web with content for adults with iptables?

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Security :: Use Of Iptables And Books For Indepth?

Jan 30, 2010

proper use of iptables and tell me good books for indepth study

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Security :: Cannot See Source On First SSH Entry In IPTables

Jul 23, 2010

Now I managed to get iptables to work with my OpenVZ configurations and everything seems to work as it should. However when I run iptables -L I can only see source for the second SSH rule, why isn't the first ones source/IP shown? Also if you have any comments about the setup feel free. I'm running SSH, Apache and local MySQL

The is simply to hide my IP's
iptables -P INPUT ACCEPT
iptables -P FORWARD DROP

iptables -F
iptables -F INPUT
iptables -F OUTPUT
iptables -F FORWARD
iptables -F -t mangle
iptables -X

iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -d -j REJECT
iptables -A INPUT -p tcp --dport 22 -s -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -s -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -m state --state INVALID -j REJECT
iptables -A INPUT -j REJECT
iptables -A INPUT -j DROP

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Security :: Detect Nmap With Iptables?

Apr 27, 2011

i have a problem with iptables when i use nmap to scan ports then ports shown.this is my rules on my firewall.Quote:

:OUTPUT ACCEPT [1002:40080]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT


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Security :: How To Disable The Iptables Permanently

Mar 5, 2011

I am using Fedora. I want to disable Linux iptables permanently. Normally when I reboot my pc the iptable service is on. how can I disable even I turn reboot the pc.

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Security :: How To Set Iptables For IPSec Tunnel?

Jan 7, 2010

I want to setup firewall protection with iptables to support IPSec tunnels. That is, the firewall will drop anything from any host if it is not from an established IPSec tunnel. And it will accept anything (any protocols) if it's from an IPSec tunnel.

That is, I need also to open up ping to make ping work. But if I open up icmp, I cannot prevent pings from hosts that's outside my IPSec tunnels. This defeats my purpose.So if my purpose is to allow "anything" within the tunnel and disallow/drop anything outside the IPSec tunnels, how should I setup the iptables rules?

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Security :: Iptables 192.168.1.x Server Can't Ping By 192.168.0.x

Jun 1, 2011

i have set firewall for centos of server like this.

it has a gateway of

iptables -P INPUT DROP
iptables -A INPUT --in-interface lo -j ACCEPT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -p tcp --destination-port 22 -m mac --mac-source 00:0F:EB:91:00:01 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 80 -m mac --mac-source 00:0F:EB:91:00:01 -j ACCEPT

the mac source is my laptop's mac address. But when i try to ping from my laptop of (my gateway is but share the same server that has 3 network gateway including gateway for the centos)it failed. what i should do to enable this ping.i also cannot connect to the centos server unless i change my ip to 192.168.1.x and same gateway as centos.can someone suggest what should i modify my firewall to enable connection to centos server from my laptop? is that related to nat and forward chain in firewall of centos?

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Security :: IPTables And SSH Rate Limiting

May 20, 2011

I'd like to discourage the SSH bots that try to log into my system (CentOSv5), and among other things, I've changed my SSH port to someting other than 22. As well, I've been playing around with the idea of some iptables rules (note port 22 is used here as example):
# Allow SSH with a rate limit
iptables -A INPUT -i ppp0 -p tcp --syn --dport 22 -m hashlimit --hashlimit 15/hour --hashlimit-burst 3 --hashlimit-htable-expire 600000 --hashlimit-mode srcip --hashlimit-name ssh -j ACCEPT
iptables -A INPUT -i ppp0 -p tcp --syn --dport 22 -j LOG --log-prefix "[DROPPED SSH]: "
iptables -A INPUT -i ppp0 -p tcp --syn --dport 22 -j DROP
I am *NOT* an iptables expert. What do you all think about the above code snip?

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