> Have you loaded the firmware first?

No, I somehow missed to look at ipwctl(8).  Thanks, I'll try it.

> My /etc/ifconfig.ipw0 has:
>	!/usr/sbin/ipwctl -f /usr/pkg/libdata/if_ipw/ipw2100-1.2.fw
> (from the ipw-firmware-1.0 package)
> 
> You will need different firmware for BSS vs IBSS mode;
> see /usr/pkg/libdata/if_ipw/README for more details.