The four onboard NICs as well as an extra 2-port NIC we installed are all GLDv3 
devices.  So, they take advantage of the new dladm command to do link 
aggregation.  We had the networking guys configure the 6 ports on the Cisco 
switch (LACP protocol) and then we did the aggregation as follows:

dladm create-aggr -P L2 -l active -d e1000g0 -d e1000g1 -d e1000g2 -d e1000g3 
-d e1000g4 -d e1000g5 18
ifconfig aggr18 plumb nvsun14 up

One would only use Sun trunking if the NICs or software could not take 
advantage of the new GLDv3 stack.  In particular, we found that the ce (Cassini 
NIC) devices will never take advantage to of the dladm aggregation.  Their 
performance is also much poorer because they bury the CPU.  So stay away from 
them.

But dladm rocks!