Conceptually, EtherChannel combines (aggregates) multiple linked ports into a single aggregate connection.
#show etherchannel load-balance
^Displays current load balancing method
#conf t
(config)#port-channel load-balance <mode>
(config)#port-channel load-balance src-dst-mac
(conifg)#show etherchannel load-balance
^Change load balancing method to load balance based on source and destination IP address
Modes:
dst-ip Destination IP address
dst-mac Destination MAC address
src-dst-ip Source & destination IP address
src-dst-mac Source & destination MAC address
src-ip Source IP address
src-mac Source MAC address
Methods to create an EtherChannel:
1) Static = Manual config
Don't do this because you want the switch to automatically remove a link when it goes down
2) Dynamic = Automatic
A) PAgP (Port Aggregation Protocol) = Cisco proprietary
B) LACP (Link Aggregation Control Protocol) = IEEE standard and preferred
(config)#interface range g0/0 - 3
(config-if-range)#channel-group 1 mode desirable
modes:
active = Enable LACP unconditionally
passive = Enable LACP only if a LACP device is detected
auto = Enable PAgP only if a PAgP device is detected
desirable = Enable PAgP unconditionally
on = Enable etherchannel only
For PAgP:
auto + auto = No EtherChannel
desirable + auto = EtherChannel
desirable + desirable = EtherChannel
For LACP:
passive + passive = No EtherChannel
active + passive = EtherChannel
active + active = EtherChannel
To config the aggregate etherchannel as a VLAN trunk, do this on both switches:
(config)#interface port-channel 1
(config-if)#switchport trunk encapsulation dot1q
(config-if)#switchport mode trunk
(config-if)#do show interfaces trunk
#show etherchannel summary
^Displays port aggregates, protocol, and which ports are being used in each
#show etherchannel port-channel
^Displays more details including the channel group mode
Layer 3 EtherChannel
(config)#int range g0/0 - 3
(conifg-if-range)#no switchport
(conifg-if-range)#channel group 1 mode active
(config-if-range)#int po1
(config-if)#ip address 10.0.0.1 255.255.255.252
[These are my notes from Jeremy's excellent CCNA course which can be viewed here.]
