In message <20041206223330.GL13128@styx.org>, ww@styx.org writes:
>On Mon, Dec 06, 2004 at 01:53:43PM -0800, Matt Thomas wrote:
>> 
>> Actually, multiple loopback devices can be useful for tcpdump or
>> just keeping statistics.  It'd be nice if you set a loopback device
>> as a null interface.  (ifconfig lo1 media null)  Then you have an
>> easy to collect counters.  (you could do the same with a reject mode).
>
>Might be nice to have a ciscoish distinction between loopback
>and null interfaces: null0 is a bitbucket, lo0 is not.
>

I've written if_null, and use it daily -- multiple instances, so I can 
run tcpdump separately on each -- but I need to check if it needs to be 
updated before I commit it.

		--Steve Bellovin, http://www.research.att.com/~smb