Cisco CCNA Preparation · lesson 15 of 36 · 25 min
What Is EtherChannel?
EtherChannel bundles multiple physical Ethernet links between two switches into a single logical link. This provides increased bandwidth (up to 8 links × link speed) and redundancy (if one link fails, traffic continues on the remaining links) — all while appearing as a single interface to STP, which prevents it from blocking the redundant links.
EtherChannel Negotiation Protocols
Key rule
At least one side must be in an active/desirable mode. Two passive or two auto sides will never form a channel.
EtherChannel Requirements
All member interfaces must have matching configuration or the channel will not form:
Configuration Commands
Reading show etherchannel summary
Flashcard Drill
EtherChannel Bundles multiple physical links into one logical link — increases bandwidth and provides redundancy. LACP IEEE 802.3ad — open standard EtherChannel negotiation. Modes: Active and Passive. PAgP Cisco proprietary EtherChannel negotiation. Modes: Desirable and Auto. LACP Active Actively initiates LACP negotiation — will form channel with Active or Passive. LACP Passive Responds to LACP but does not initiate — needs Active on the other side. PAgP Desirable Actively initiates PAgP negotiation — will form channel with Desirable or Auto. channel-group 1 mode active Assigns interface to EtherChannel group 1 using LACP Active mode. show etherchannel summary Shows EtherChannel groups, member ports, and their status flags. Port-channel interface The logical interface representing the EtherChannel bundle — configure VLANs/trunking here. STP and EtherChannel STP sees the EtherChannel as one link — does not block redundant physical members.
Knowledge Check
EtherChannel — 10 Questions
What is the primary benefit of EtherChannel?
- Encrypts traffic between switches
- Bundles links for more bandwidth and redundancy
- Replaces VLANs
- Eliminates the need for STP
Answer: Bundles links for more bandwidth and redundancy
EtherChannel combines multiple physical links into one logical link for bandwidth and redundancy.
Which EtherChannel protocol is an open IEEE standard?
- PAgP
- LACP
- CDP
- LLDP
Answer: LACP
LACP (IEEE 802.3ad) is the open standard. PAgP is Cisco proprietary.
Two switches are configured with LACP Passive on both sides. Will an EtherChannel form?
- Yes
- No — at least one side must be Active
Answer: No — at least one side must be Active
Passive + Passive will not form a channel. At least one side must be Active.
The PAgP mode that actively initiates negotiation is _____.
Answer: Desirable
PAgP Desirable actively initiates negotiation. Auto only responds.
Which command creates an EtherChannel using LACP Active on interfaces g0/1 and g0/2?
- channel-group 1 mode passive
- channel-group 1 mode active
- etherchannel group 1 lacp
- port-channel 1 active
Answer: channel-group 1 mode active
channel-group 1 mode active assigns the interface to group 1 using LACP Active.
EtherChannel member interfaces can have different speeds.
- True
- False
Answer: False
All EtherChannel member interfaces must have the same speed and duplex.
Where should you configure VLAN/trunk settings for an EtherChannel?
- On each physical member interface
- On the port-channel logical interface
- On the switch globally
- On the root bridge
Answer: On the port-channel logical interface
Configure VLANs and trunking on the port-channel interface — it applies to all member links.
Which command verifies EtherChannel group status and member port flags?
- show interfaces
- show vlan brief
- show etherchannel summary
- show ip route
Answer: show etherchannel summary
show etherchannel summary shows all EtherChannel groups, member ports, and status flags.
STP will block redundant physical links inside an EtherChannel bundle.
- True
- False
Answer: False
STP sees the EtherChannel as a single logical link — it does not block individual member ports.
In show etherchannel summary, the flag _____ indicates a port is bundled in the EtherChannel.
Answer: P
P = Port bundled in EtherChannel. I = standalone, D = down.
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