EtherChannels

EtherChannels

• Cisco offer another method to scale link bandwidth by Aggregation Parallel link turn the ether channel technology.
• An EtherChannel is a way of combining several physical links between switches into one logical connection. 
• Normally, Spanning Tree blocks redundant links; EtherChannels get around that and enable load balancing across those links. 
• Traffic is balanced between the channel links on the basis of such things as source or destination MAC address or IP address. 
• The EtherChannel load-balancing method is configured at global configuration mode. 
• A logical interface—called the Port Channel interface—is created. Configuration can be applied to both the logical and physical interfaces.

Terms for EtherChannel Configuration

• Can consist up to maximum 8 physical port.
• All ports must be the same speed and duplex.
• All ports in the bundle should be enabled.
• None of the bundle ports can be a SPAN port.
• Interfaces in the channel do not have to be physically next to each other or on the same module.
• Assign an IP address to the logical Port Channel interface, not the physical ones, if using a Layer 3 EtherChannel.
• Put all bundle ports in the same VLAN, or make them all trunks. If they are trunks, they must all carry the same VLANs and use the same trunking mode.
• The configuration you apply to the Port Channel interface affects the entire EtherChannel. The configuration you apply to a physical interface affects only that interface.

Types of EtherChannel

1. PAGP – Port Aggregation Protocol
2. LACP – Link Aggregation Control Protocol

1. PAgP – Port Aggregation Protocol

• The Cisco proprietary Port Aggregation Protocol (PAgP)
• Provide Automatic EtherChannel configuration between switch.

There are three PAgP modes:

1. On: The port channels without using PAgP negotiation. The port on the other side must also be set to On. 
2. Auto: Responds to PAgP messages but does not initiate them. Port channels if the port on the other end is set to Desirable. This is the default mode. 
3. Desirable: Port actively negotiates channeling status with the interface on the other end of the link. Port channels if the other side is Auto or Desirable.

PAgP Configuration

Figure: EtherChannel-PAgP

Switch A

Switch-1#configure terminal
Switch-1(config)#interface range e0/0- 3
Switch-1(config-if-range)#channel-protocol pagp
Switch-1(config-if-range)#channel-group 1 mode desirable
Switch-1(config-if-range)#Exit or Ctrl+Z

Switch B

Switch-1#configure terminal
Switch-1(config)#interface range e0/0- 3
Switch-1(config-if-range)#channel-protocol pagp
Switch-1(config-if-range)#channel-group 1 mode desirable
Switch-1(config-if-range)#Exit or Ctrl+Z

PC 1

IP Address: 192.168.5.1
Subnet: 255.255.255.0

PC 2

IP Address: 192.168.5.2
Subnet: 255.255.255.0

Check EtherChannel Configuration Status

# show running-config interface number
# show interfaces number etherchannel
# show etherchannel number port-channel
# show etherchannel summary
# show etherchannel load-balance

2. LACP – Port Aggregation Protocol

• Link Aggregation Control Protocol (LACP) is an IEEE standard protocol. 

There are three LACP Modes

• On: The port channels without using LACP negotiation. The port on the other side must also be set to On. 
• Active: Port actively negotiates channeling with the port on the other end of the link. A channel forms if the other side is Passive or Active. 
• Passive: Responds to LACP messages but does not initiate them. A channel forms only if the other end is set to Active. 

If you want to use LACP, specify it under the interface and put the interface in either active or passive mode:

(config-if)# channel-protocol lacp
(config-if)channel-group number mode {active/passive}

LACP Configuration

Figure: EtherChannel-LACP

Switch A

Switch-A#configure terminal
Switch-A(config)#interface range e0/0- 3
Switch-A(config-if-range)#channel-protocol lacp
Switch-A(config-if-range)#channel-group 1 mode active
Switch-A(config-if-range)#Exit or Ctrl+Z

Switch B

Switch-B#configure terminal
Switch-B(config)#interface range e0/0- 3
Switch-B(config-if-range)#channel-protocol lacp
Switch-B(config-if-range)#channel-group 1 mode active
Switch-B(config-if-range)#Exit or Ctrl+Z

PC 1

IP Address: 192.168.5.1
Subnet: 255.255.255.0

PC 2

IP Address: 192.168.5.2
Subnet: 255.255.255.0

Check EtherChannel Configuration Status

# show running-config interface number
# show interfaces number etherchannel
# show etherchannel number port-channel
# show etherchannel summary
# show etherchannel load-balance