CCNP Exam Prep Tips and Must Knows

Things You Need to Know about Link Aggregation with EtherChannel

EtherChannel

• Solution to provide more bandwidth
• Logical aggregation of similar links
• Provides load balancing and redundancy
• Supported for switch ports routed ports

PAgP and LACP

• Protocols to negotiate the Etherchannel link
• PAgP is Cisco proprietary
• LACP is IEEE  802.3ad standard
• Static Etherchannel configuration without protocol

PAgP Mode

• On: channel member without negotiation (no protocol)
• Desirable: Actively ask if the other side can/will become an Etherchannel
• Auto: Passively wait for the other side to ask
• Off: Etherchannel not configured on interface

LACP Mode

• On: channel number without negotiation (no protocol)
• Active: actively asked if the other side can/will become an Etherchannel ARP
• Passive: passively wait for other side to ask
• Off: Etherchannel not configured on interface

All interfaces within an Etherchannel must have same attributes:

• Same speed and duplex
• Same mode (access or trunk)
• Same native and allowed VLANS on trunk ports
• Same access VLAN on access ports
• Same MTU size
• Configure parameters on port-channel interface

Make sure you can configure:

• LACP
• PAgP
• Statically configured EtherChannel  

Know how to:

• Identify which protocol is being used to form Etherchannel

Make sure you are familiar with output:

• Show etherchannel summary
• Show etherchannel

Show interface [  ] etherchannel