DFT Wiki

When the network grows and the traffic increase the Trunks between switches start to become the weakness of the system.

If this only cable break the whole communication is lost, and all the traffic shares the bandwidth of only one port:

Simply adding another cable does not really solve all the problems:

The protocol STP will automatically block one of the ports to avoid looping in the network and the data traffic will still be limited to one port with one spare connection in case something happens with the principal.

EtherChannel creates one virtual interface margin up to 8 port. The new connection is as fast as the sum of the bandwidth of each port.

enable 
configure terminal 
no ip domain lookup
line con 0
logging synchronous
hostname Switch1

enable 
configure terminal 
no ip domain lookup
line con 0
logging synchronous
hostname Switch2

Set EtherChannel Static:

interface range g0/1-2
channel-group 1 mode on

interface range g0/1-2
channel-group 1 mode on

Set EtherChannel to negotiate via PAgP protocol (Cisco):

interface range g0/1-2
channel-group 1 mode desirable

interface range g0/1-2
channel-group 1 mode desirable

Set EtherChannel to negotiate via LACP protocol:

interface range g0/1-2
channel-group 1 mode active

interface range g0/1-2
channel-group 1 mode active

No EtherChannel:
– Single Port Speed
– 1 spare Port

EtherChannel:
– Dual Port Speed
– No spare port but in case of any go down the other honds the traffic.

Definitions os the Modes:

• ON – ON
  • Enforces to form the link aggregation.
• Desirable – Desirable
  • Both will initiate the negotiation and form the link.
• Desirable – Auto
  • One side will initiate and the other side will be able to continue the negotiation to form the link.
• Auto – Auto
  • Both sides will wait but will NOT initiate the negotiation, so they will NOT form the link.
• Active – Active
  • Both will initiate the negotiation and form the link.
• Active – Passive
  • One side will initiate and the other side will be able to continue the negotiation to form the link.
• Passive – Passive
  • Both sides will wait but will NOT initiate the negotiation, so they will NOT form the link.

To check the configuration in each Switch issue the commands:

show spanning-tree
show etherchannel summary
show interfaces port-channel 1

EtherChannel can also be used on Access ports, but most frequently will be used on Trunk ports since they are naturally neck to the traffic.