EtherChannel and Link Aggregation Flashcards

What is the primary purpose of EtherChannel on a Cisco switch?

Answer: To bundle multiple physical links into a single logical link for increased bandwidth and redundancy

EtherChannel aggregates multiple physical Ethernet links into one logical link, multiplying bandwidth and providing redundancy without Spanning Tree blocking ports.

Which Cisco-proprietary protocol is used to negotiate EtherChannel formation between switches?

Answer: PAgP

Port Aggregation Protocol (PAgP) is Cisco's proprietary protocol for automatically negotiating EtherChannel bundles between Cisco devices.

Which IEEE standard defines the Link Aggregation Control Protocol (LACP)?

Answer: IEEE 802.3ad (802.1AX)

LACP is defined in IEEE 802.3ad, later incorporated into IEEE 802.1AX, and is the vendor-neutral standard for link aggregation.

What is the maximum number of physical links that can be bundled in a single EtherChannel on a Cisco switch?

Answer: 8

A Cisco EtherChannel supports up to 8 active physical links bundled into a single logical port-channel interface.

Which PAgP mode causes a port to actively send PAgP packets to initiate an EtherChannel?

Answer: Desirable

PAgP 'desirable' mode actively initiates EtherChannel negotiation by sending PAgP packets, similar to LACP 'active' mode.

Which LACP mode will form an EtherChannel only if the remote side also sends LACP packets?

Answer: Passive

LACP 'passive' mode will only respond to LACP packets; it does not initiate negotiation, so the remote side must be in 'active' mode.

What load-balancing method does Cisco use by default for EtherChannel traffic distribution?

Answer: Source MAC address

Cisco's default EtherChannel load-balancing method is based on source MAC address, though this can be changed with the 'port-channel load-balance' command.