In a typical configuration where trunks are configured, the member links of the trunk are
connected through Ethernet cables to corresponding links on a peer system.
This figure shows an example of a typical trunk configuration with two peers and three member links on each peer:
A primary goal of the trunks feature is to ensure that frames exchanged between peer systems
are never sent out of order or duplicated on the receiving end. The BIG-IP®
system is able to maintain frame order by using the source and destination addresses in each
frame to calculate a hash value, and then transmitting all frames with that hash value on the
same member link.
The BIG-IP system automatically assigns a unique MAC address to a trunk. However, by default, the MAC address that the system uses as the source and destination address for frames that the system transmits and receives (respectively), is the MAC address of the lowest-numbered interface of the trunk.
The BIG-IP system also uses the lowest-numbered interface of a trunk as a reference link. The BIG-IP system uses the reference link to take certain aggregation actions, such as implementing the automatic link selection policy. For frames coming into the reference link, the BIG-IP system load balances the frames across all member links that the BIG-IP system knows to be available. For frames going from any link in the trunk to a destination host, the BIG-IP system treats those frames as if they came from the reference link.
Finally, the BIG-IP system uses the MAC address of an individual member link as the source address for any LACP control frames.