Etherchannel Notes
Etherchannel
– It’s an interfaced bundling technology
– Used to group up to 8 (2 to 8) similar interfaces
-> Must have same properties
-> Speed
-> Duplex
-> Interface mode
-> Access
-> Trunk
-> VLAN-ID (for access ports)
– Protocols can be used to configure the etherchannel
-> Port Aggregation Protocol (PAgP)
-> Master – desirable
-> Slave – auto
-> Link Aggregation Control Protocol (LACP)
-> 802.1ad
-> Can have up to 8 backup interfaces
-> Master – active
-> Slave – passive
-> Manual etherchannel configuration
-> only keyword is “on”
SW1(config)# int range fa0/1 – 2
channel group 5 mode { desirable | auto | active | passive | on }
show etherchannel sum
Po1 SU Fa0/1(P), Fa0/2(P)
L3 Ehterchannel
SW1(config)# int range fa0/1 – 2
no switchport
– “no switchport” must be configured before the channel-group configuration
LACP
– Uses concept of Master / Slave to decide negotiator
– Master is elected according to lower priority
-> Default system priority – 32768
-> Then lowest MAC address
-> Lowest Port-ID used first
– Negotiator (Master) determines which ports are used
-> Other ports become backup ports (if more than 8 are configured)
SW1(config)# lacp system-priority 100
Once master is elected, port-priority can be used to decide which ports are used
– Lower is better (default is 32768)
SW1(config)# int range fa0/9 – 16
lacp port-priority 100
Load Balancing Mechanism
– 9 algorithms are available to decide exit interface
– Only 1 algorithm can be configured
– Sending side affected only
– Single input
-> src-ip
-> dst-ip
-> src-mac
-> dst-mac
-> src-port
-> dst-port
– Dual input
-> src-dst-ip
-> src-dst-mac
-> src-dst-port
src-dst-ip
– Source IP: 10.0.0.1 (0000 0001)
– Source IP: 10.0.0.2 (0000 0010)
– Destination IP: 10.0.0.5 (0000 0101)
– 2 links
-> last bit
– 3 to 4 links
-> last 2 bits
– 5 – 8 links
-> last 3 bits
XOR used for dual input algorithms
SW1(config)# port-channel load-balance { src-ip | dst-ip | src-mac | dst-mac | src-port | dst-port | src-dst-ip | src-dst-mac | src-dst-port }
