[geeks] Seeking network direction.

[Joshua Boyd]

I'm trying to understand somethings about how ethernet works.  I  
would be happy for either answers, or pointers to free resources  
containing the answers would be even better.

When I plug an ethernet device into an ethernet switch/network, what  
happens below the IP level?

I was talking to someone with a weird problem.  His device would talk  
to his PC when connected via cross-over.  When both were plugged into  
a Cisco 2900 switch, communications between the devices would work,  
but the show-mac-addresses (or whatever the specific command is  
because I'm not a cisco guy) wouldn't show the device's MAC, but the  
LEDs showed a connection was made.  When plugged into a Cisco 3550, a  
connection was shown, but no communications happened between any  
other PC and the device.

I know that ARP used to map IP addresses to MAC addresses (data link  
layer addresses), and I know that MAC addresses are to uniquely  
identify devices on an ethernet network and I know about ethernet  
frame sizes, but I know nothing else about ethernet and how devices  
negotiate.  Is this what the spanning tree protocol does?

Also, what is the relationship between AUI, AAUI, MII, and the phy  
chip on a embedded design that seems to say it speaks MII?  Also, I  
seem to recall once setting up a box with a lot of 15 pin connectors  
on it.  I believe a AUI adapter went on one of these to connect this  
box to a Cat5 switch, while the other 15 pin connectors were  
connected via 15 pin cables directly to an Onyx, a Sun 4/330, and a  
few IPC/IPX machines.  What was that thing?  It was considered  
somewhat out dated when I was touching it in the 1996ish time range.   
I think it was referred to as a thicknet hub.

Anyway, I've been flipping through wikipedia and google, but I don't  
feel I've found the answers to these questions.  It isn't essential  
that I find them, but I don't like knowing there are things out there  
related to what I work on that I know so little about.