From owner-freebsd-doc  Wed Sep 10 12:41:02 1997
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Date: Wed, 10 Sep 1997 12:40:51 -0700 (PDT)
From: David Holloway <daveh@berzerkeley.com>
To: freebsd-doc@freebsd.org
Subject: iijppp which -alias option
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Update with better information

/usr/sbin/ppp -alias

addresses this situation, http://www.freebsd.org/FAQ/FAQ125.html#125

equivalent to linux use of ip-masquerading.
(terminology may be in debate here but the job is done)