Introduction
Etherchannel (also referred to as "Fast Etherchannel" or simply "trunking") is a scheme to trunk together multiple 10/100 Mb/s Ethernet links to form a single, fat pipe in order to:
- load-balance traffic over the physical links; and
- recover from link failures.
In what follows, the terms "Etherchannel" and "trunking" are used interchangeably.
Why Etherchannel?
- Etherchannel provides a fat pipe by linking together multiple 10/100 BaseT links.
- Etherchannel provides load-balancing of traffic over the physical links.
- Etherchannel provides recovery from link failures.
- Etherchannel uses 10/100BaseT technology as its core. This leverages investments in existing network infrastructure (UTP wiring, 10/100 switches, etc.). The only thing required is a software upgrade on switches, routers and servers.
- Even though Gigabit Ethernet products are shipping, products that enable Gigabit Ethernet over copper (4 pairs of UTP cabling) are not going to be shipped for a several years. Etherchannel gives customers reluctant to switch to fiber in the LAN backbones an alternative to Gigabit Ethernet.
As mentioned above, the basic idea in Etherchannel is really simple. The idea is to take some (small number) of Ethernet links and trunk them together. Most switches/routers provide trunking of 2 to 4 links. This trunk looks like a single network pipe to the upper layers (and is administered as a single network pipe). Load balancing is achieved by distributing traffic out onto the physical links. The distribution of outgoing traffic over the links forming the trunk is described below. Furthermore, a trunk with N links can recover from failure of any (N - 1) links by distributing traffic over the remaining links.
Basically, there are two parts to Etherchannel. The first deals with how the links are configured to form a trunk. The second deals with how traffic flowing out on the trunk is load-balanced over the physical links.
Let's proceed further and we will see how to configure a Layer 3 Ether channel using the PAgp Protocol (Port Aggregation Protocol) 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 3 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 connected to Giga Ethernet ports 0/1,0/2,0/3 and 0/in Cisco 3560 Catalyst Switch ITKESW02.
The configuration is as follows
Configuration in the Cisco 3560 Catalyst Switch ITKESW01
ITKESW01#config t
ITKESW01(config)# interface port-channel 1
ITKESW01(config-if)# no switchport
ITKESW01(config-if)# no shutdown
ITKESW01(config-if)# ip address 192.168.1.1 255.255.255.0
ITKESW01(config-if)# end
ITKESW01#config t
ITKESW01(config)# interface range gigabitEthernet 0/45 – 48
ITKESW01(config-if-range)# no switchport
ITKESW01(config-if-range)# no ip address
ITKESW01(config-if-range)# channel-group 1 mode desirable
ITKESW01(config-if-range)#end
Note: This example shows how to configure Gigabit Ethernet ports 0/45 – 0/48 into port channel 1 with PAgP mode desirable
Note: The "no switchport" command is required to change interface from layer2 to layer3 mode.
Configuration in the Cisco 3560 Catalyst Switch ITKESW02
ITKESW02#config t
ITKESW02(config)# interface port-channel 1
ITKESW02(config-if)# no switchport
ITKESW02(config-if)# no shutdown
ITKESW02(config-if)# ip address 192.168.1.2 255.255.255.0
ITKESW02(config-if)# end
ITKESW02#config t
ITKESW02(config)# interface range gigabitEthernet 0/1 – 4
ITKESW02(config-if-range)# no switchport
ITKESW02(config-if-range)# no ip address
ITKESW02(config-if-range)# channel-group 1 mode auto
ITKESW02(config-if-range)#end
Note: This example shows how to configure Gigabit Ethernet ports 0/1 – 0/4 into port channel 1 with PAgP mode auto
Note: The "no switchport" command is required to change interface from layer2 to layer3 mode.
Do use "show etherchannel" command to display port-channel information after configuration and remember to save the configuration.
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 7
Now it's the time to proceed further and we will see how to configure a Layer 2 Etherchannel using the LACP Protocol (Link Aggregation Protocol) 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 desirable mode) 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 desirable n-isl trunking 1
Gi0/46 desirable n-isl trunking 1
Gi0/47 desirable n-isl trunking 1
Gi0/48 desirable n-isl 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 lacp
Note: LACP protocol is configured to be used in this channel
ITKESW01 (config-if-range)# channel-group 1 mode active
Note: A logical port-channel interface is automatically created when ports are grouped into a channel group.
Configure the mode active to be used in LACP
Configuration in the Cisco 3560 Catalyst Switch ITKESW02
ITKESW02#sho interfaces trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable n-isl trunking 1
Gi0/2 desirable n-isl trunking 1
Gi0/3 desirable n-isl trunking 1
Gi0/4 desirable n-isl 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 lacp
Note: LACP protocol is configured to be used in this channel
ITKESW02 (config-if-range)# channel-group 1 mode active
Note: A logical port-channel interface is automatically created when ports are grouped into a channel group.
Configure the mode active to be used in LACP
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) LACP 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) LACP Gi0/1 (P) Gi0/2 (P) Gi0/3 (P) Gi0/4 (P)
ITKESW02#
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 6
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#
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 5
Now let's see what options are available for load balancing in an Etherchannel bundle. How does the Cisco Catalyst Switch determines which physical link in the Etherchannel bundle to use to forward the data?
The answer is the Cisco Catalyst Switch uses a polymorphic algorithm taking key fields from the header of the packet to generate a hash to a physical link in the Etherchannel group.
Data sent across an Etherchannel is not load-balanced equally between all interfaces. Etherchannel utilizes a load-balancing algorithm, which can be based on several forms of criteria, including:
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 4
The automate creation of an Etherchannels group can occur only when the Cisco Switches are running same Etherchannel protocols. Using different Etherchannel protocols at each end will not work. One more important criterion for the automated creation of the Etherchannel is the links must share the similar physical characteristics.
Configuration of ports into an Etherchannel are based on pre defined Etherchannel modes that are assigned as a default or modified via user configuration to an Ethernet port. There are five Etherchannel modes, which can be used for automated creation of an Etherchannel .
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 3
Basically there are two types of protocols are available, which can be used to bundled the automated creation of an Etherchannel in the Cisco Catalyst Switches.
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 2
· An Etherchannel Group Number must be in the range of 1 to 256.
· All ports in the target Etherchannel group MUST be in the same VLAN.
· If one physical link in the Etherchannel group is a TRUNK, then all other ports must be configured as trunks carrying the same VLAN information.
· Any defined broadcast limits must be the same across all ports in an Etherchannel.
· An LACP Etherchannel group cannot support any physical links in half duplex mode.
· No port in the Etherchannel group can be defined as a SPAN port.
Cisco Etherchannel Overview and how it can be configured in Cisco Catalyst Switches – Series 1
An Etherchannel combines multiple physical links into a single logical link that provides aggregate bandwidth of 800 MBPS (fast Etherchannel, full duplex) , 8 GBPS (Giga Etherchannel) or 80 Gbps (10 Giga Ethernet) . Ideal for load sharing or link redundancy – can be used by both layer 2 and Layer 3 subsystems and Etherchannel can provide network managers with a reliable, high-speed solution for the campus network backbone. EtherChannel technology was invented by Kalpana in the early 1990s. They were later acquired by Cisco Systems in 1994. In 2000 the IEEE passed 802.3ad which is an open standard version of EtherChannel.
I would like to explain some key points about Etherchannel using graphical diagrams so that it's easy understand and to remember.
Etherchannel can be configured defined on Ethernet, Fast Ethernet, Giga Ethernet or 10 Giga Ethernet ports
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