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Re: Smurfing

  • From: David J. Schmidt
  • Date: Mon Feb 16 00:57:06 1998

On Fri, 13 Feb 1998, Randy Bush wrote:

> >  o All router administrators on the immediately reachable
> >    Internet needs to turn off directed broadcasts on their router
> >    interfaces.  It's conceivable that "a significant portion of
> >    all" would do as well, but the magnitude of this problem
> >    boggles the mind.  First of all, we'd need to distribute the
> >    appropriate amount of clue to all the corners of the net where
> >    this needs to happen.  Maybe, just maybe, we'll get there
> >    sometime (I'm an optimist!).
> why should this not have become the default mode for all vendor diustributed
> router code?
> randy

While I would argue that directed broadcasts should be off by default, I
recently read RFC 1812 (Requirements for IP Version 4 routers) and found
the following in section 

 (d) { <Network-prefix>, -1 }

         Directed Broadcast - a broadcast directed to the specified
         network prefix.  It MUST NOT be used as a source address.  A
         router MAY originate Network Directed Broadcast packets.  A
         router MUST receive Network Directed Broadcast packets; however
         a router MAY have a configuration option to prevent reception
         of these packets.  Such an option MUST default to allowing

Until the RFC gets modified router vendors will probably allow reception
of directed broadcasts by default to remain compliant with RFC 1812.

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