*BSD News Article 76961


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From: azrael@chopin.postech.ac.kr (Kim Tae Hyoung)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: tcpdump
Date: 27 Aug 1996 02:38:18 GMT
Organization: POSTECH, Pohang, Korea
Lines: 54
Distribution: world
Message-ID: <4vtn2q$one@news.postech.ac.kr>
References: <4vpifm$9jo@nuscc.nus.sg> <4vrir5$io0@uriah.heep.sax.de> <4vsncn$4ok@usenet.srv.cis.pitt.edu>
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Carl Joel Kuzmich (cjk@omedsrvb.omed.pitt.edu) wrote:

: In article <4vrir5$io0@uriah.heep.sax.de>, j@uriah.heep.sax.de (J
: Wunsch) writes:
: |>csclailf@leonis.nus.sg (Lai L F) wrote:
: |>
: |>> When I try to use tcpdump, I got an error messages as follow:
: |>> 
: |>> tcpdump: /dev/bpf0: Device not configured
: |>> 
: |>> How do I configure this device??
: |>
: |>pseudo-device bpfilter 4
: |>
: |>-- 
: |>cheers, J"org
: |>
: |>joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC:
: |>JW11-RIPE
: |>Never trust an operating system you don't have sources for. ;-)
: |>
: |>

: Why "4" and not "8" or some other value???

Well.. I think it's not serious.
"4" is from 'LINT' file, maybe.

see following text from handbook
------------------------------------------
pseudo-device bpfilter number

    Berkeley packet filter. This pseudo-device allows network interfaces to be 
	placed in promiscuous mode, capturing every packet on a broadcast network 
	(e.g. an ethernet).  These packets can be captured to disk and/or examined 
	with the tcpdump(1) program. Note that implementation of this capability can 
	seriously compromise your overall network security. The number after bpfilter 
                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^
	is the number of interfaces that can be examined simultaneously. Optional, 
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	not recommended except for those who are fully aware of the potential 
	pitfalls. Not all network cards support this capability.
------------------------------------------

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