What is EtherChannel / Link Aggregation – simply put it can provide fault-tolerant high-speed links between Switches, Routers, and Servers, by combing physical links together to represent a logical link, a maximum of 8 links can be combined at one time although 16 links are possible, however 8 of which are placed in standby.
There are two protocols used for negotiating EtherChannel / Link Aggregation:
Port Aggregation Protocol (PAgP) has two Channel modes and they are “Desirable” and “Auto”. (Cisco Propriety)
Link Aggregation Control Protocol (LACP) has two Channel modes and they are “Active” and “Passive”. (Industry Standard)
A few guidelines before implementation:
Make sure to check the ports that will be involved with the negotiation on both sides.
Make sure that the protocols for negotiating are the same one both sides.
Check to see if Speed,Duplex match.
Check to see if the VLANS match , All interfaces in the EtherChannel bundle must be assigned to the same VLAN or be configured as a trunk.
TIP: Shut down the ports before the configuration then bring them up again once done