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186726Re: Possible SPAM mitigation trick

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  • Wietse Venema
    Nov 22, 2005
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      Nathanael Hoyle:
      > >>The IP is a network boundary address. i.e., if it were a class C
      > >>network (/24). the address would be x.x.x.0, rather than 1-254 or
      > >>broadcast (255). Because this IP refers to the *network* rather than a
      > >>host therein, it cannot actually be assigned to a host. This means I
      > >
      > >
      > > Oh yes it can.
      > >
      > > Your broadcast address is meaningful only for hosts on your subnet.
      > >
      > > Your broadcast address has no meaning for hosts on other subnets.
      > >
      > > Assign your broadcast address to an MX host record, and clients will
      > > experience TCP timeout waits just as if they connect to a host that
      > > is turned off.
      > >
      > > Wietse
      >
      > If you would please note, I used the bottom end network boundary, not
      > the top-end broadcast address. To my understanding, this would be
      > accurate in describing broadcast address behavior, but not network
      > boundary address behavier. Would this in fact still apply for, for
      > intance the .0 address in a class C?

      It does not matter.

      The all-bits-0 (old broadcast) and all-bits-1 broadcast address
      have meaning only for hosts on your own subnet.

      The all-bits-0 (old broadcast) and all-bits-1 broadcast address
      have no meaning for hosts on other subnets.

      Assigning either of these to an MX host record means that clients
      will experience TCP timeout waits just as if they connect to a host
      that is turned off.

      Wietse
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