ENC(4)                    OpenBSD Programmer's Manual                   ENC(4)

NAME
     enc - Encapsulating Interface

SYNOPSIS
     pseudo-device enc 4

DESCRIPTION
     The enc interface is a software loopback mechanism that allows hosts or
     firewalls to filter ipsec(4) traffic using ipf(5). The vpn(8) manpage
     shows an example of such a setup.

     The other use of the enc interface is to allow an administrator to see
     outgoing packets before they have been processed by ipsec(4), or incoming
     packets after they have been similarly processed, via tcpdump(8).

     The ``enc0'' interface inherits all IPsec traffic.  Thus all IPsec traf-
     fic can be filtered based on ``enc0'', and all IPsec traffic could be
     seen by invoking tcpdump(8) on the ``enc0'' interface.

EXAMPLES
     To see all outgoing packets before they have been processed via ipsec(4),
     or all incoming packets after they have been similarly processed:

     #> ifconfig enc0 up
     #> tcpdump -i enc0

SEE ALSO
     tcpdump(8), bpf(4), inet(4), ipsec(4), netintro(4), ipf(5), vpn(8)

OpenBSD 2.9                     October 7, 1999                              1
