Dual Nics

[Overkill]

Has anyone noticed that even if you use two network cards that only one 
nic is really doing all the traffic.  I noticed this with many different 
types of network cards and nics.  I even setup snmp monitoring, cacti, 
etc and noticed that both IP's and one interface is doing all the work.  
Even setup bonding and still does the same thing.

Is this a driver issue or am I simply not using enterprise hardware?

-Overkill