ifconfig fails to report promisc mode. This more probably is a linux
kernel thingy as far as I can tell, because ifstatus also will not
show promisc mode.
Sorry for the lack of information, but i'm kinda bogged down :)
/usr/sbin/tcpdump -n -w blah &
no PROMISC flag shows.
This is a tcpdump bugture/featlet. Changing component.
Fixed (by updating tcpdump man page) in tcpdump-3.4-22.