CCIE R&S Written Overview: Etherchannel

Etherchannel

• Used to aggregate bandwidth of physical links

– Same logic as PPP Multilink

• Consists of two parts

– Port-Channel interface

• Logical interface representing the link bundle

– Members interfaces

• Physical links part of a link bundle

• Channel can be any type of interface

– i.e. layer 2 access, trunk, tunnel, or layer 3 routed

EtherChannel Negotiation

• channel-group [number] mode [mode]

• Mode determines how negotiation occurs

– On

• No negotiation

– Desirable & Auto

• Initiate or listen for PAgP

– Active & Passive

• Initiate or listen for LACP

• PAgP vs. LACP

– Like ISL vs. 802.1q

EtherChannel Mode Compatibility

• On –On

• Desirable – Desirable

• Desirable – Auto

• Active – Active

• Active – Passive

EtherChannel Load balancing

• Load balancing between member interface based on…

– Source MAC address

– Destination MAC address

– Source IP Address

– Destination IP Address

– Combinations of the four

• Modified with…

– port-channel load-balance

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