I wants supose that hlapex or l2phx are not working in that server, because if the answer is yes, is working, there is no sense in find other sniffer.
But, if is not working, you can find in google a sniffer with decoders included.
I was proving one a time ago (i don´t remember the name) that had a decoder to be used in the l2 packets.
Google is the light in the tunel.-