When I type:
ethereal -i ath0 -L
(-i required, as ath0 is not default)
I get:
Data link types (use option -y to set):
  DLT 1 (Ethernet)
  DLT 127 (IEEE 802.11 plus BSD WLAN header)
  DLT 105 (IEEE 802.11 Wireless LAN)

I should also mention that a kernel panic can occur when using monitor
mode if transmit rates have not been pre-set. See PR kern/29442.
Also kismet is a good program for monitoring wireless. Their currently
is no NetBSD package for this. I have patched kismet for NetBSD, but the
method I used is not in a format that can be submitted to the kismet
people. I used the FreeBSD portions as a base, and then added the
features that the FreeBSD version did not have, such as current channel
display, signal level, acpi battery monitor.

On Thu, 10 Mar 2005 14:09:31 -0600
"John Maier" <jmaier@midamerica.net> wrote:

> i'm not sure what you mean by 'prime it' because when type:
> 
> >ethereal -L
> Data link types (use option -y to set):
>   DLT 1 (Ethernet)