• 255.255.255.255

    From rmbandes@gmail.com@21:1/5 to herrman...@gmail.com on Thu Apr 27 06:58:17 2017
    On Tuesday, September 27, 2016 at 5:19:30 PM UTC-4, herrman...@gmail.com wrote:
    I am working on getting some diskless Sun machines running again.

    At one point in booting, the host broadcasts to a server using 255.255.255.255.
    Specifically, this is contacting the bootparamd server.

    Compiling bootparamd on either FreeBSD or Linux, it does not
    receive such requests. Compiling on OS X, it does.

    I have rarp, tftp, and nfsd running on FreeBSD just fine, but
    can only complete the boot with bootparamd on OS X.

    In more detail, it works like this:

    Client broadcasts (not using IP) to an RARP server,
    to ask for its IP address.

    RARP server unicasts the reply (again, not IP).

    Client unicasts using UDP to a tftp server, using the
    server address of the replying RARP server. Using
    TFTP, it downloads the boot program.

    Boot program runs, and uses RARP to again ask for
    its IP address. (It isn't passed through from above.)

    Client broadcasts to UDP/IP address 255.255.255.255
    for a bootparamd server.

    Using the callbootd test program, I can verify that the
    server responds to unicast requests on both FreeBSD
    and Linux.

    I use the same C source, and same /etc/bootparams file
    on all hosts, though with changes in #include file names
    that are system specific. (Such as the directory for rpc.h.)

    Are all hosts supposed to accept UDP broadcasts to 255.255.255.255?

    thanks,

    -- glen

    All hosts should accept incoming IPv4 packets with a destination address of 255.255.255.255, the Limited Broadcast Address, if they receive it. Packets sent to this address will not pass through routers, so if there is a router between the sender and
    your intended recipient, the recipient isn't receiving it. You can verify this with tcpdump.

    Ron

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