EtherChannel (LACP/PAgP)
Aggregate multiple links for bandwidth and redundancy
Lesson 1: EtherChannel Fundamentals
EtherChannel combines 2-8 physical links into one logical link. Benefits: Increased bandwidth (up to 800Mbps on 100Mbps links), automatic failover redundancy, STP sees as single link (no blocking). All links must have identical speed, duplex, and VLAN configuration.
Lesson 2: LACP vs PAgP Protocols
LACP (Link Aggregation Control Protocol): IEEE 802.3ad standard, vendor-neutral. Modes: Active (initiates negotiation), Passive (waits). PAgP (Port Aggregation Protocol): Cisco proprietary. Modes: Desirable (initiates), Auto (waits). Best practice: Use LACP for interoperability.
Lesson 3: Configuration Guidelines
Requirements: Same speed/duplex on all ports, same VLAN/trunk config, compatible channel mode. Commands: 'channel-group X mode active/on/desirable'. Verify: 'show etherchannel summary'. Layer 2: Port-channel. Layer 3: Routed port-channel.
Lesson 4: Load Balancing Methods
Distributes traffic across links based on: src-mac, dst-mac, src-dst-mac (default), src-ip, dst-ip, src-dst-ip. Configure: 'port-channel load-balance method'. Choose based on traffic pattern for optimal distribution.
Lesson 5: Troubleshooting EtherChannel
Common issues: Mismatched configurations (speed/duplex/VLAN), wrong channel modes (both passive/auto won't form), spanning-tree inconsistencies. Check: 'show etherchannel port-channel', 'show run interface', verify physical layer first.