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Karma Yogi
Asked: 2023-11-15 14:38:54 +0800 CST

Does ip6tables support tcp-flags?

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I have below command

ip6tables -A INPUT -m ipv6header --header hop,dst,route,frag,auth,esp,none,prot --tcp-flags ACK SYN

But getting error as ip6tables v1.8.4 (legacy): unknown option "--tcp-flags"

I have tried --tcp-flags option with iptables, It works fine. But in ip6tables, it gives error

ip6tables

2 Answers

  1. Best Answer

    quote from man ip6tables

    These extensions are loaded if '--protocol tcp' is specified. It provides the following options:

    add the argument --protocol tcp.

    ip6tables -A INPUT -m ipv6header --header hop,dst,route,frag,auth,esp,none,prot \
    --protocol tcp --tcp-flags ACK SYN
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  2. According to the man page, --tcp-flags is part of an extension that is loaded if --protocol tcp is specified. Your command line does not seem to specify --protocol tcp, hence the extension is not present and the option is not available.

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