The magic is when using multiple VLANs:
1) Don't use the real VLAN ID for the trunk PVID unless you know for certain that was set on the switch. It is stripped off of all packets, and who knows what the PVID of the switch is, if any.
2) Any mismatch between PVID on the SEA and the trunk will cause packets to be dropped.
3) Don't use IEEE VLAN mode for the client adapter unless you're going to add VLAN interfaces from AIX. When not in VLAN mode, the PVID is ADDED to all packets on client adapters.
4) When using multiple trunks on one SEA, they all have to be the same trunk priority. ha_mode=sharing balances not using trunk priority, but based on the order of the virt_adapters field.