North American Network Operators Group

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Re: Smurfing

  • From: Craig A. Huegen
  • Date: Fri Feb 13 19:06:14 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? 

Because the routing RFC[1] states:

---
   A router MAY have an option to disable receiving network-prefix-
   directed broadcasts on an interface and MUST have an option to
   disable forwarding network-prefix-directed broadcasts.  These options
   MUST default to permit receiving and forwarding network-prefix-
   directed broadcasts.
---

"network-prefix-directed broadcasts" are the ones spoken of here.

A router *MUST* have an option to turn them off and *MUST* default to
forwarding them.  The "MAY" stated here (to clarify) means that the router
MAY choose not to respond to another host pinging a broadcast address.

[1] RFC-1812, "Requirements for IP Version 4 Routers"; F. Baker; June
    1995.

/cah