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Hello, i got advice to Only allow RELATED,ESTABLISHED TCP/UDP connections for other ports such as 53 (DNS). so i want to ask what command i need to use to do ...
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  1. #1
    Linux User postcd's Avatar
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    How to allow only RELATED,ESTABLISHED TCP/UDP connections


    Hello,

    i got advice to Only allow RELATED,ESTABLISHED TCP/UDP connections for other ports such as 53 (DNS).

    so i want to ask what command i need to use to do this for port 53 on linux with iptables?
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  2. #2
    Linux Guru Rubberman's Avatar
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    What you are trying to accomplish is not clear. Please try to explain further what your aims are.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
    Linux User postcd's Avatar
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    How to allow only RELATED,ESTABLISHED TCP/UDP connections for port 53?
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  4. #4
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    I presume you're asking about iptables and not wanting to rewrite the kernel? It does make it easier for people to be helpful if you're more explicit in your ask.

    DNS is a bad example to choose - it don't think it has RELATED ports. For the protocols that do iptables uses helper modules. I'm not an iptables expert but here's some info that might help: Netfilter Helpers

  5. #5
    Linux Guru Lazydog's Avatar
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    RELATED,ESTABLISHED only refer to TCP connections. UDP is a connection-less protocol. That being said it would be very helpful to know what your end goal is here as Rubberman had asked. This will get you what you exactly need to do to accomplish the task you are trying to complete with the least amount of down time.

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    Robert

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