CentOS 5 :: Possible To Stop Anything Being Added To Iptables?

Mar 3, 2009

I seem to be having an issue with iptables, every so often the server starts loosing packets and then goes off completley, if I manage to login to ssh I can stop iptables and this resolves the problem, however it keeps doing this. Is it possible to stop anything being added to iptables?

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Networking :: IPtables Resets Counter When Rules Added

May 19, 2011

Whenever I add a rule to iptables, all of the policy counters reset. The counters for each individual rule remain intact, however, the main counter resets. Here's what I mean:

[root] ~ # iptables -vL
Chain INPUT (policy ACCEPT 65M packets, 83G bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 50M packets, 30G bytes)
pkts bytes target prot opt in out source destination .....

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CentOS 5 :: Custom Iptables: Remove The Existing Iptables First?

Apr 28, 2009

To expand: I'm trying to set up a box with l7-filter, and I need to patch and compile iptables as part of the process. I ./configured it with the prefix= argument so it would install into /sbin instead of /usr/sbin, and I did a yum remove iptables before installing it so as not to get in the way of the original iptables, but I'm wondering if this is really necessary - it's kind of annoying, because removing the original iptables removes the init.d script, deregisters the service, etc. If I don't, is it possible that iptables might get overwritten in a system update or something, or will yum see that I've got a custom/newer version in there and leave it be?

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Fedora :: Can Make Libvirtd Stop Tempering With Iptables

May 6, 2010

I'm using fedora12 with KVM. I'm also using iptables for filtering and nat. Problem is when I start libvirtd, it overwrites my current iptables and iptables config file (/etc/sysconfig/iptables).

Ok it leaves an old copy in /etc/sysconfig/iptables.old, but the main problem is that it removes also all my custom settings from filter and my full nat. I would like the keep control on my iptables and like to manage them on my own. But I cant find an option in the libvirtd config files and/or the libvirtd startup scripts to prevent libvirt from changing my iptables. how I can make libvirtd stop tempering with my iptables?

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Networking :: Stop IPTables To Resolve Source Address?

Oct 25, 2010

Here is a glimpse of my IPTABLES
I see in the column of sources the addresses being resolved to domain names is there a way I can stop this?

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CentOS 5 Hardware :: Added HDD Does Not Show More Space Overall

Oct 10, 2009

I have a CentOS V5.3 system with a single 30GB HDD having about 21 GB of free space. I added a 40 GB HDD with a single ext3 partition. After reboot, the free space still reads as 21 GB. I ran the LVM GUI, and added the volume to the LVM group 00; no change to the free space after reboot. I ran the LVM again, removed the volume from the group and created a new group for the volume; still no change after reboot. I am clearly missing a key operation.

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CentOS 5 :: Samba PDC Not Allowing Computer To Be Added

Jul 29, 2010

Samba 3.5 Centos 5.5

I am trying to attempt to set up a samba ldap PDC server.

When I try and connect a computer to the network I get error 'Username could not be found'

I have included smbldap.conf ##smbldap.conf
slapd.conf ##slapd.conf
the smb.conf ##smb.conf
the results of slapcat ##slapcat
the eriror log for log.roor ##log.root

The error I marked as interesting ##interesting , shows that it can't create the user or maybe something else. But up until that time there didn't seem to be a problem.



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CentOS 5 Hardware :: Added HDD - Server Fails To Restart

Apr 27, 2010

I have a issue that could get me fired, so I would appreciate your input. My knowledge about linux is limited
The company I work for has a Dell Poweredge 6850 that keeps pretty much everything (databases, websites, etc). The server had a Virtual Drive created from 2 Physical Drives. Since the HDD space was getting low, we got a new drive, inserted it, formatted and rebooted the system. But the system now refuses to start, giving an FAILED message, something related to EXT2 partition that cannot be read at /dev/hda1

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CentOS 5 :: RSYNC: Listing Files Added & Changed?

Oct 21, 2010

I'm using rsync to create a mirror of the data files on our main server every day. I've looked at the man page, and can't see it; can I get a listing of the files that have been changed on or added to the mirror when it's completed? Can it just log what it's doing to a file?

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CentOS 5 Hardware :: 5.3 - 4Gb RAM Added - Boot Fails - Can't See Login Screen

Jul 9, 2009

I have a Dell precision 380 (system specs can be found here: [URL]. My system is set-up in dual boot configuration with Windows Xp x64 on one side of my HD and CentOS 5.3 (64bit) on the other. My system came with 2Gb (2 x 1Gb) of RAM and I recently wanted to upgrade. I bought 2 x 2Gb ELIXER DDR2 667Mhz RAM. I carefully added the new sticks to my motherboard, booted up windows via bios which noticed the new RAM was present. All seemed well.

However, on rebooting the system and entering the CentOS boot phase, after the boot phase (eg starting program... [ok] etc) but before the login screen my screen goes black / blank. My system has an ATI FireGL v3100 graphics card, I checked out the technical info on this and it should be ok on 64 bit linux. (See: [URL])


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CentOS 5 :: Added Gnome And X To Command Line Only Install - How To Make X Start At Boot

Nov 5, 2009

I've got an install of CentOS 5.3 in a VM which was installed without X or Gnome.I've added X (yum groupinstall 'X Window System') and Gnome (yum groupinstall 'GNOME Desktop Environment) and can now run startx no problem.However on boot I get a command line login rather than the graphical login screen one normally gets if Gnome is included at install time.What do I need to do to get the graphical login after boot?

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CentOS 5 Server :: VsFTP Iptables Wont Start Get Error - CentOS 5.5

May 11, 2011

i am currently trying to install vsFTP onto my new linux server and btw i just started using linux today this is my first time using linux so i got the ftp installed good it got downloaded and everything then i went to open a port for my server for vsFTP i used this comand to open it "-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT" then i closed it by pressing ESC then :wq! and it brought me back to my comand line again so now when i try to start the ip table thing with the comand "service iptables start" then when i execute that comand putty respondes with this "Applying iptables firewall rules: iptables-restore: line 1 failed [FAILED]"

The install Guide im using: [URL]

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CentOS 5 :: Configure Iptables Except Using Terminal?

Mar 19, 2009

can i configurfe iptables except using terminal ? like 32-bit interface application

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CentOS 5 :: Iptables-1.3.5-5.3 Missing Libipt_time.so?

Oct 22, 2009

I have just done the upgrade to CentOS 5.4, but it seems that the iptables library libipt_time.so is no longer provided in /lib/iptables in the distribution. The currently installed version is iptables-1.3.5-5.3

I am getting this error message: iptables v1.3.5: Couldn't load match `time':/lib/iptables/libipt_time.so: cannot open shared object file: No such file or directory

Have the -m time components been moved to another library or removed from iptables? How do I stop iptables from trying to load this non-existent library?

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CentOS 5 Networking :: Iptables U32 Does Not Work

Apr 7, 2010

When I try something like, I get:

iptables -A FORWARD -p udp -m length --length 39 -m u32 --u32 '27&0x8f=7' --u32 '31=0x527c4833' -j DROP
iptables: No chain/target/match by that name.

So I re-compiled the kernel enabling WAN Router, and all the subsections. Downloaded latest iptables, removed the RPM one, installed the iptables from source.. Guess what, same error!

PS: iptables -m u32 -h works, it displays a page of info.

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CentOS 5 :: Setting Up Iptables For Symmetric NAT?

Apr 14, 2011

I am having difficulties setting up Symmetric NAT through iptables and I hope you can help me with this issue. First things first: "A symmetric NAT is one where all requests from the same internal IP address and port, to a specific destination IP address and port, are mapped to the same external IP address and port.If the same host sends a packet with the same source address and port, but to a different destination, a different mapping is used. Furthermore, only the external host that receives a packet can send a UDP packet back to the internal host."

Need: I am working on a SIP application and SIP apps face a problem with NATed networks. STUN is a solution to such a problem and my SIP application has an embedded STUN client functionality. Scenario and Technical Details:


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Security :: Iptables Not Opening Port On Centos?

Dec 24, 2010

I'm trying to open port 119. I already have a few ports open. I've used webmin to open both incoming and outgoing ports. iptables --list --numeric gives me:

ACCEPT tcp -- tcp dpt:10000


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CentOS 5 Networking :: Iptables Empty After Reboot?

Aug 5, 2009

I have a strange problem with IpTables.after a server reboot, the complete rule-list of iptables is empty. After a manually start, all my old rules are there again.I checked chkconfig if autostart of iptables is enabled:chkconfig --list iptablesiptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off

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CentOS 5 Networking :: Firewall Insanity Iptables And Apf Don't Seem To Like Each Other?

Aug 13, 2009

I'm at my wits end at this point.

CentOS 5
APF 9.7
Webmin 1.4.80 (yes i can be a gui noob at times)

I'm currently running a dedicated server that hosts a couple of sites and runs a game server or two. I was using iptables on its own for a while, but recently I'm a target of all sorts of attacks (typically aimed directly at the gameserver on port 7777. UDP flood attacks, etc). I'm also seeing an spike in foreign spam, SSH brutes, and a few people in Turkey thought it would be cute to download files over and over and over I have decided to start banning entire countries, using the subnets listed here [URL]... I'm trying to block Central and South america (189,190,200,201.x.x.x), China, Ukraine, Turkey, Iran, Spain and Italy. I do this because a majority of the traffic from those areas are usually up to no good.

I installed APF so I could easily add these ranges in deny_hosts.rules and be done with it. I added the ranges, which turned out to be too many, and the system tanked. I decreased the amount of ranges to just 4:

Restarted APF and it loaded fine. Do an apf --list and iptables --list and it shows those 4 ranges as blocked. The only issue...I have people from 190.x and 200.x connecting to the gameserver and PLAYING. Its as if the firewall isnt there. Also, adding those ranges to /etc/hosts.deny (or whatever) doesn't block them either.

I add one of my own ips and I get blocked instantly. WTF?? I look in the iptables for webmin, and it shows an empty firewall. I do iptables --list and it shows the ranges I added in APF. I'm looking at building (or whatever its called) an fresh iptables with the geoip module added in. [URL]...

I've never done anything like this, and I don't want to kill the box. I also don't want to spend the effort if 1) something is wrong with my system to begin with and 2) the geoip module doesn't work. geoip module aside....how exactly should i configure the firewall? Empty iptables completely and then rely on APF for everything? Oh and heres another tidbit: I tried this before 2 years ago and it used to be that anything I put in APF would show when i looked at iptables using the webmin module. Thats no longer the case now. That was also on CentOS 4 when it did that. I don't know if moving to 5 is whats preventing it now.

In a nutshell, I'm new at this and I'm being inundated with terrible people trying to do terrible things and I'm ready to just give up. Can someone just give me a quick rundown on:

1) how to test that my firewall is actually firewalling

2) how I should configure the/a firewall on this CentOS5. Not too specific, I just want to know if I should empty iptables then load apf, should i not bother with APF (i like it when it works), is there a specific order of doing things?

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CentOS 5 Networking :: Iptables Not Loading Some Modules?

Jan 23, 2010

The problem I am having is that iptables won't load the required modules for my firewall rules.

iptables -F
iptables -P INPUT DROP
iptables -P FORWARD DROP


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CentOS 5 Networking :: Iptables For Transparent Proxy?

Mar 11, 2010

I have big problem with correct settings of iptables as a router. My network topology (UTM Hardware router)>eth0 with apache ftp and transparent squid 8080)--->eth1 with dhcp)


I have problem with hanging connections through squid which are very slow or connection failed. Sometimes i received DNS timeout error from squid stable 2.6 21


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CentOS 5 :: Can't Initialize Iptables Table `tproxy'

Mar 26, 2010

# iptables -t tproxy -n -L iptables v1.3.5: can't initialize iptables table `tproxy': Table does not exist (do you need to insmod?) Perhaps iptables or your kernel needs to be upgraded. Does exist a tproxy module for CentOS's kernel (2.6.18) ?

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CentOS 5 Networking :: Error When Redirect Through Iptables?

Mar 30, 2010

I'm trying to redirect the requests from port 80 to ports 8080 and 8081 through iptables because I've got two services which need accept requests from the same port(80):

iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8080-8081

The problem is that the second port (8081) never gets a request, just the first one.

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CentOS 5 Networking :: Adding Iptables -F To Boot?

Sep 5, 2010

How I add this " iptables -F " to my Servers boot I already asked this from my Provider, but it seams he forget each time I ask.

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CentOS 5 Networking :: Large Iptables Rule Set?

Jan 10, 2011

Loaded up Centos 5.5 final. Configured iptables to block regions of the world based on networks. An example would be:


My /etc/sysconfig/iptables file contains about 10k entries like this. If I use this, the machine lags hardcore network wise.

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CentOS 5 Networking :: Iptables DOS Temporarily Block IP?

May 5, 2011

I have the requirement that if our website receives 20 or more requests within 60 seconds, to block the offending IP address for 5 minutes, then allow them access again. My only certain mechanism to do this is iptables. I wrote the following series of commands:

iptables -N RATE_CHECK
iptables -N DOSAttack
iptables -N RemoveBlock


I am limited in my testing, but the little I have been able to test seems to be having no effect. will the above commands have the desired effect.

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Security :: CentOS 5.5 Upgrade - IPTables SSH Auto Blocking

Jun 6, 2011

I have a fiberoptic broadband 20MB synchronous pipe at my home. Over summer at my place of employment its pretty much dead for 3 months so when I'm not busy I play around on my home server. I have my 20mb pipe going directly into my wrt54gl, from there I have a wired connection going to my server (Centos 5.3 recently upgraded to 5.5 through updates.) It serves as a file server(Samba, SSH). My wrt54gl handles natting port 22 to my server. I have my wireless AP setup to hand out leases from .2-.20 and my server has a static of .100. Dyndns.org handles my name resolution via their free account method.

I have a Mac Pro, iMac, Macbook, and a Toshiba Laptop with 64bit 7 running off wireless along with our cell phones, and my XBOX 360 also is wired directly for the gaming speed. I use all of the computers around my home to access the samba shares via unc path for file sharing and or working on projects. I had originally planned to upgrade the wrt54gl with a cisco e3200 or an e3000 but unfortunately I've come to find out dyndns and the e lines of cisco wireless AP's dont work with dyndns and get banned. So I would have to install the daemon on my server and put it as a directly connected server to my WAN link and install a second ethernet card and pass traffic through my server for the rest of my home which I am not going to do.

All of the previous sentence because it would update dyndns with a 192.168.x.x address since its not directly connected. I use a combination of putty.exe and vnc viewer to tunnel 5900 through port 22 to my server. So from anywhere I am at I can access my screen securely and then rdp or vnc to the desktop of my local LAN computers. This allows me to only have port 22 open. I've been looking at my ssh logs and noticed I have been getting hit alot with ssh scans. I want to implement an iptables firewall on my linux machine just for the purpose of further securing port 22. I dont necessarily need natting on the iptables firewall but all I need is ssh in and out, web in, and samba out to local ip's only.

For SSH this is what I want. I want to allow SSH from any IP but if it tries to login more than 3 times in one minute I want to block that IP for a full minute before it can try 3 more attempts. I also would like log to a file but have been having issues getting that to work as well. That way when I review logs and I see that an ip tries three times and then waits a minute and tries three more, etc... I can permanently block that ip or range of ip's by adding it to the iptables script. Here is my current iptables script and it doesnt seem to be working for me. I have played with this and read for almost two weeks and still cannot get it to work correctly.

# In order to use this iptables firewall script you must have iptables installed. You also must be using a 2.4.x series Kernel, with iptables suppport compiled into it, which is standard for most newer linux distributions.
# If you need help compiling iptables into your kernel, please see our kernel Compile/Upgrade Guide located at [URL]
# Once the script has been edited with all your relevant information (IP's Network Interfaces, etc..) simply make the script executable and run it as root.
# chmod 700 fw_rules.sh
# ./fw_rules.sh .....

# Our final trap. Everything on INPUT goes to the dropwall
# So we don't get silent drops.
$IPT -A INPUT -j dropwall

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CentOS 5 Networking :: IPTables Service Failed To Start

May 9, 2009

I have CentOS 5.2 just installed and massively updated with yum -update command. Than I tried to configure firewall. After changes via system_config_securitylevel_tui (open ssh, http, ftp, and 3306:TCP ports) iptables service can't start with message

> /sbin/service iptables start
Flushing firewall rules: [OK]
Setting chains to policy ACCEPT: mangle filter nat [OK]
Unloading iptables modules: [OK]
Applying iptables firewall rules: iptables-restore v1.3.5: Couldn't load match `TCP':/lib64/iptables/libipt_TCP.so: cannot open shared object file: No such file or directory
Error occurred at line: 18
Try `iptables-restore -h' or 'iptables-restore --help' for more information.

I erased the iptables service and installed it again with yum. How can I make this service work?

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CentOS 5 Networking :: View The Packets Saved By Iptables?

Jun 26, 2009

if am using --log-prefix "BANDWIDTH_OUT:" --log-level 7 to capture packets, I think is there a way to view these?

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CentOS 5 Networking :: IPtables Module Load Fail

Apr 10, 2010

I'm encountering a known problem with IPtables. I set up rules and apply them, restarting firewall, then I get this message:

Flushing firewall rules: [ OK ]
Setting chains to policy ACCEPT: raw nat mangle filter [ OK ]
Applying iptables firewall rules: [ OK ]
Loading iptables additional modules: ip_conntrack_ftp ip_conntrack_netbios_ns [FAILED]

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