Not set DF bit in IP header - Linux

This is a discussion on Not set DF bit in IP header - Linux ; Hi, We are finding that Linux will set DF bit in IP header by default. Does anybody know how to make Linux to not set DF bit in Linux by default? Thanks! CY....

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Thread: Not set DF bit in IP header

  1. Not set DF bit in IP header

    Hi,

    We are finding that Linux will set DF bit in IP header by default.
    Does anybody know how to make Linux to not set DF bit in Linux by
    default? Thanks!

    CY.

  2. Re: Not set DF bit in IP header

    "cyril.li@gmail.com" writes:
    > We are finding that Linux will set DF bit in IP header by default.


    That's called 'path MTU discovery', defined in RFC1191 (this text is
    meanwhile nearly eighteen years old and one would assume that everyone
    dabbling in transport-level network programming had at least heard of
    it ...).

    > Does anybody know how to make Linux to not set DF bit in Linux by
    > default?


    Either system-wide by writing a 1 to /proc/sys/net/ipv4/ip_no_pmtu_disc
    or per-socket by using the SOL_IP socket option IP_MTU_DISCOVER (=>
    ip(7)).


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