From: "Garrett" <glc at c dash email dot com>

>> There is a reason we use the LAN and OPTx names.  There are some things
> that
>> can only be done from a LAN interface, and some things that can only be
> done
>> from an OPTx interface.

> Are these restrictions/abilities documented any where?

Yes, but it is not always easy to find.  One example that comes to mind is 
bridging. http://doc.m0n0.ch/handbook/examples-filtered-bridge.html tells 
you how to do it, and tells you to use an OPT interface.  This is because 
there is not option for it on the LAN interface.  However, that is not 
explicitly stated in the handbook.

                            Lee