Jan 6 2009 6:11AM GMT
Posted by: Yasir Irfan
Cisco,
Cisco Systems,
Cisco Tips,
Etherchannel,
Etherchannel configuration,
Etherchannel restrictions,
Switches,
Switching,
Layer 2 EtherChannel Configuration,
PAGP EtherChannel Configuration,
LACP,
Cisco 3560 Catalyst Switch
In the previous five posts I was talking about the Etherchannel , types of protocols used , rules and restrictions applied to an Etherchannel . Now it’s the time to see how an Etherchannel can be configured in a Cisco Catalyst Switch.
An Etherchannel in a Cisco IOS can be defined as Layer 2 Etherchannel or a Layer 3 Etherchannel.
For a Layer 2 Etherchannel, physical ports are placed into an Etherchannel group.

For a Layer 3 Etherchannel, layer 3 SVI (Switch Virtual Interface) is created, and then the physical ports are placed into an Etherchannel group which is bound to the L3 SVI.

Now let’s see how to configure a Configure a Layer 2 Etherchannel in a Cisco Catalyst Switch using a PAGP (port aggregation protocol) Protocol. In my previous posts I did discussed about the PAGP protocol, it’s a Cisco proprietary protocol, can be applied only in Cisco Catalyst Switches.
Here is the scenario which we will follow

From the above diagram we have two Cisco 3560 Catalyst Switches named ITKESW01 and ITKESW02.
We will configure a Layer 2 Etherchannel between the Cisco 3560 Catalyst Switches ITKESW01 and ITKESW02. The Giga Ethernet ports 0/45, 0/46/,0/47 & 0/48 on a Cisco 3560 Catalyst Switches ITKESW01 are trunk ports and they are connected to Giga Ethernet ports 0/1,0/2,0/3 and 0/4 (also trunk ports) in Cisco 3560 Catalyst Switch ITKESW02.
The configuration is as follows
Configuration in the Cisco 3560 Catalyst Switch ITKESW01
First run the command “Show interfaces trunk
ITKESW01#sho interfaces trunk
Port Mode Encapsulation Status Native vlan
Gi0/45 on 802.1q trunking 1
Gi0/46 on 802.1q trunking 1
Gi0/47 on 802.1q trunking 1
Gi0/48 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/45 1-4094
Gi0/46 1-4094
Gi0/47 1-4094
Gi0/48 1-4094
Port Vlans allowed and active in management domain
Gi0/45 1
Gi0/46 1
Gi0/47 1
Gi0/48 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/45 1
Gi0/46 1
Gi0/47 1
Gi0/48 1
ITKESW01#
Second Step configure the Giga Ethernet ports 0/45 to 0/48 in the Etherchannel
ITKESW01#config t
ITKESW01(config)# interface range gigabitEthernet 0/45 – 48
ITKESW01(config-if-range)#channel-protocol pagp
Note: PAgP protocol is configured to be used in this channel
ITKESW01 (config-if-range)# channel-group 1 mode desirable
Note: A logical port-channel interface is automatically created when ports are grouped into a channel group.
Configure the mode desirable to be used in PAgP
Configuration in the Cisco 3560 Catalyst Switch ITKESW02
ITKESW02#sho interfaces trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Gi0/2 on 802.1q trunking 1
Gi0/3 on 802.1q trunking 1
Gi0/4 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Gi0/2 1-4094
Gi0/3 1-4094
Gi0/4 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Gi0/2 1
Gi0/3 1
Gi0/4 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Gi0/2 1
Gi0/3 1
Gi0/4 1
ITKESW02#
Second Step configure the Giga Ethernet ports 0/1 to 0/4 in the Etherchannel
ITKESW02#config t
ITKESW02(config)# interface range gigabitEthernet 0/1 – 4
ITKESW02(config-if-range)#channel-protocol pagp
Note: PAgP protocol is configured to be used in this channel
ITKESW02 (config-if-range)# channel-group 1 mode auto
Note: A logical port-channel interface is automatically created when ports are grouped into a channel group.
Configure the mode auto to be used in PAgP
Now run show command to display the Etherchannel configurations on the Cisco 3560 Catalyst Switches ITKESW01 and ITKESW02
ITKESW01#sho etherchannel 1 summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
u - unsuitable for bundling
U - in use f - failed to allocate aggregator
d - default port
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
——+————-+———–+———————————————–
1 Po1(SD) PAgP Gi0/45 (P) Gi0/46 (P) Gi0/47 (P) Gi0/48 (P)
ITKESW01#
ITKESW02#sho etherchannel 1 summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
u - unsuitable for bundling
U - in use f - failed to allocate aggregator
d - default port
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
——+————-+———–+———————————————–
1 Po1(SD) PAgP Gi0/1 (P) Gi0/2 (P) Gi0/3 (P) Gi0/4 (P)
ITKESW02#
In upcoming posts I will show how to configure a Layer 2 Etherchannel using LACP protocol