Ether Channel
If we paid hefty amount for each individual links between the 2 Switches & all of those links are in Discarding Mode & only 1 is used due to STP/RSTP then we need a port bundling mechanism to group those ports as 1 single port.
Ether Channel is the solution to bundle multiple ports/links as a single logical link.
Ether Channel is the logical aggregation of similar links.
Ether Channel does Load Balancing between those links.
Ether Channel provides Redundancy for up to 16 links.
Ether Channel works only on directly connected Switches.
In STP/RSTP convergence starts as soon as there is a change in Topology/link fails. But now as we are grouping the links & treating them as 1 single link so even if one of the link goes down from a particular group convergence won't start. Convergence will take place only if the entire group/channel goes down.
Guidelines:
All interface in an Ether Channel must be configured at the same Speed & Duplex.
All interface in an Ether Channel must support the same allowed range of VLANs.
In L2 Ether Channel, Interfaces must be assigned to the same VLAN/Configured as Trunk.
In L3 Ether Channel, IP Addresses must be assigned to port-channel logical interfaces.
Ether Channel Protocols:
PAGP (Port Aggregation Protocol):
Cisco Proprietary works only on Cisco Switches.
Has Desirable & Auto modes like 802.1Q modes.
LACP (Link Aggregation Control Protocol):
Open Standard works on all the Switches.
Has Active & Passive modes like Active & Passive Modes of PAGP.
Reference:
CCNA 200-301 OCG, Volume 1, Pg. 234 - Wendell Odom.
RST Notes
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