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

NAME
     enc - Encapsulating Interface

SYNOPSIS
     pseudo-device enc 1

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 incom-
     ing packets after they have been similarly processed, via tcpdump(1).

     There is only one enc interface, named ``enc0'', regardless of the argu-
     ment given on the pseudo-device line in the kernel configuration file.

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(1),  bpf(4),  inet(4),  ipsec(4),  netintro(4),  ipf(5),  vpn(8)

BUGS
     The PROMISC flag is not cleared on the enc0 interface after tcpdump is
     stopped.

OpenBSD 2.6                     October 7, 1999                              1
