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Chapter 15 - firewalls


I've collected several questions. Pls help me to fins the answer.I'm usuing CentOS7
1.I've disabled the firewalld (systemctl disable firewalld systemctl stop firewalld). I've configured the iptables with the iptables CMD.It's Ok. What the different the iptables/netfilter and firewalld ? How to do it correctly ? Must firewalld be stopped not to use it together with iptables/nftables? Any compatibility between firewalld and iptables ?
2. Chapter - Distribution Default:
It's possible to find /etc/sysconfig/iptables-config and /etc/sysconfig/ip6 tables-config instead of /etc/sysconfig/iptables. Is it the same file ?
3. How to save all my settings for the iptables not to lost it after rebooting ?
There is no the "service iptable save" command! As backup It's possible to save as the iptables-save > /root/ iptables.backup and iptables-restore < /root/iptables.backup . I think it's better than nothing but how to save it correctly ?
4. What do you mean " service iptables stop" ? You mean SysV , don't you ? I think Systemd is everything. There is no iptables/iptablesd. I cannot find systemctl status iptablesd. this is no here --> "systemctl | grep iptables" Is it possible to check the status with systemctl (not iptables -L)?
5. Where can I find the logs about unsuccessful connection attempts for the iptables ? Can i find statistics/logs If the connections are established ? Must " -j LOG..." be added to all rules where I'd like to see established connections ?
6. Firewalld is compatible with nftables. When about the iptables ? Does iptables compatible with nftables ?



  • AlexeyBY

    Pls let me know some example about the Mangle table ? When must the table be used ?

  • lee42x
    lee42x Posts: 380

    There is no "must use" tables, only common or optional configurations.
    The "mangle" table is generally used for changing the packet, like changing the MTU size or the RTT. Features of the less common tables "mangle","raw" and "security" are not covered in detail in this course.
    Please see "man iptables" for additional information on the tables "mangle","raw" and "security" tables.

  • lee42x
    lee42x Posts: 380

    iptables and firewall-cmd are both configuration programs that can configure netfilter firewalls, they use different configuration files. Firewalld package has a monitoring service called "firewalld" that implements the configuration created by "firewall-cmd" and friends.

    As for the iptables vs iptqbles -config files in /etc/sysconfig, one file describes the iptables commands to netfilter and the other configures the environment for the iptables module. iptables-config is well documeted in the file.

    Sorry, missed a "service" command, it will be purged.
    You can use "iptables-save" and "iptables-restore".

    Use the "LOG" target.

    Yes, firewalld can configure iptables or nftables.
    iptables is not intended to configure nftables.
    nft configures nftables.
    There are of course exceptions and compatibility modes to migrate configurations and commands. Migration & conversion features are out of scope for this chapter.

    Regards Lee

  • AlexeyBY

    As far as I understand there are two ways how to configure the netfilter -- iptables and firewalld. Don't they interfere one with one ? What is the best way to configure netfiler - iptables ? firewalld ? it's better to add some labs about firewalld.

    As for saving configurations of the netfilter which is configure with iptables, I can set iptables-save but the configuration is deleted as soon as OS is rebooted. any other way ?

    As for the "LOG" target, it's additional CMD. If i got wrong and something didn't work Would it possible to find unsuccessful connection attempts ? E.g. would i found anything in my OS about attempts if "iptables -P INPUT DROP " and "iptables -P FORWARD DROP " were set ?

    Thank you

  • coop
    coop Posts: 915

    firewalld is covered in some detail in LFS201, and iptables etc in LFS211 so as to avoid repetition. YOu should have taken LFS201 before LFS211 as a pre-req (or the equivalent of course).

    iptables-save saves the configuration. That is where its name comes from. Iptables-restore restores it. That is why it has restore in the name. It saves the configuration in /etc AFAIK.

    It might be more productive if you put perhaps a little more effort into answering questions yourself before asking on the forum, just because this is not a real time chat and it is not unusual to wait 24 hours or more to get a response. iptables does have quite a bit of stuff in it, and while it is all conceptually not hard there is just a lot of things to absorb. (which is why we hold back on it in LFS201 and do it in LFS211) It will eventually be a diminishing legacy infrastructure, but not yet.

  • AlexeyBY

    Hello coop,
    Hope everything is Ok on your side.
    Have you ever read you labs ? I mean theory and practice too. For example, It is really funny to see that the NFS is tested with loopback( instead of creating a simple topology with two OS. Why cannot I answer questions here. I've lost my money pls lose your time to answer for questions. Pls be informed it's impossible to perform the most of the labs step by step due to your mistakes :) I suggest asking Google to understand topics how to prepare the course.

    I've read the LFS201. I've asked here the best practice how to do it. This course(LFS211) is theoretical which cannot be used at all in production setup.

    As for the configurations , A script must be created to load the iptables-restore after rebooting an OS.

    So be polite the next time before chatting here. Probably you don't know Linux is open source word :)

    Thank you. I'm waiting for your thanks for me because i'm improving your course with my messages here!


  • coop
    coop Posts: 915
    edited October 2020

    sigh. You oscillate between nice and being abusive. You should read your posts before sending and think about what kind of response they are likely to inspire.

    You should understand that thousands of students have taken these courses without the constant kinds of problems you are running into and asking for immediate help. Sure there are mistakes here and there and differences because there are many different Linux distributions and versions even with distributions (Centos 7 vs 8, Ubuntu 20.04 vs 18.04 vs 16.04, Debian, Fedora etc) so a little patience on your side would be appreciated. Statments like "cannot be used at all" are not likely to engender patient and friendly response. or "Pls be informed it's impossible to perform the most of the labs step by step due to your mistakes" when thousands of students have done precisely that -- successfully complete the labs and learn from them.

    I am not going to engage on this further because I am not an expert much less the expert on this course. Remember the live instructor version of this course has a list price of about $3K; you cannot get that instant help in the e-learning course.

  • AlexeyBY

    Ha-ha. relax! Checking NFS with a loopback is funny. why not ))))
    I wanted to pay $3K for LFS422 but...I lose my interest. If you cannot create a good lab for so easy topics how can...



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