North American Network Operators Group

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Re: Smurfing

  • From: Dean Anderson
  • Date: Fri Feb 13 18:59:17 1998

At 5:52 PM -0500 2/13/98, 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 routers used by regular companies on their intranets generally need
to propogate directed broadcasts so that protocols and software that use
directed broadcasts in a subnetted environment will work properly. Its only
at the borders of other companies (such as ISP's) that directed broadcasts
have to be turned off.

Even ISP's that use things like HPOV SNMP host discovery internally need to
permit internal directed broadcasts.  But they shouldn't go outside your
network, and you probably don't want them coming in from the outside to
your internal network.

It would be a bad default, since the less experienced net-admin at a
private company might not understand why broadcasts don't work, whilst the
more sophisticated net-admins supposedly found at ISP's and NSP's know
about these things, and usually have some tools to quickly configure
routers in cookie-cutter fashion, making the defaults unnecessary ;-)


           Plain Aviation, Inc                  [email protected]