2.1.e Implement and troubleshoot EtherChannel

2.1.e [i] LACP, PAgP, manual

The LACP (802.3ad) for Gigabit Interfaces allows bundling individual Gigabit Ethernet links into a single logical link that provides the aggregate bandwidth of up to 4 physical links.

All LAN ports on a port channel must be the same speed and must all be configured as either Layer 2 or Layer 3 LAN ports. If a segment within a port channel fails, traffic previously carried over the failed link switches to the remaining segments within the port channel. Inbound broadcast and multicast packets on one segment in a port channel are blocked from returning on any other segment of the port channel.

PAgP packets are sent between Fast EtherChannel-capable ports to negotiate the forming of a channel. When PAgP identifies matched Ethernet links, it groups the links into an EtherChannel. The EtherChannel is then added to the spanning tree as a single bridge port.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1668-1676).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750e_3560e/software/release/12-2_55_se/configuration/guide/3750escg/swethchl.html

http://www.ciscozine.com/configuring-link-aggregation-with-etherchannel/