Here we go,we are coming to the conclusion of the Ether channel series, I my self learned a lot and enjoyed while writing posts. Hope some of you are benifited from this series. Just before concluding this series,  I would stongly recommend you guys to check this wonderful quick learning module from Cisco Systems. which foucses on layer-2-design which might be helpful to you guys.

Let’s proceed further and we will see how to configure a Layer 3 Etherchannel 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.

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#

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

 Hope it’s going to be a good beginning in the year 2009 and lest hope to see the peace and harmony all over the world.

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:

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  .