Port Aggregation Configurations

Overview of Port Aggregation

The following sections provide information about port aggregation, aggregation group, load balance, system priority and port priority.

Port Aggregation

Port aggregation allows you to group multiple physical ports into one unit. Port aggregation is useful for implementing load balancing and provides a redundant link backup.

To allow port aggregation, the basic configuration on all the ports must be consistent. The following list details the basic configuration parameters that should be consistent on all the ports:

  • STP configurations, including STP enable or disable, STP priority, and STP cost.

  • VLAN configurations, including permitted VLANs on a port and port VLAN ID (PVID).

  • Port attribute configurations, including port speed, duplex mode, and link type.


    Note

    Only full duplex mode is supported.

    Trunk, hybrid, or access link types are supported.

If the attributes of a port in an aggregation group on the same device is modified, then all the remaining ports in the group are automatically synchronized.

Aggregation Group

Port aggregation groups can be configured in the following modes:

  • ON mode: Adds a port to a static aggregation group. Link Aggregation Control Protocol (LACP) is not required in this mode to negotiate with the device at the end. A static aggregation group can have up to eight ports.

  • Active mode: Adds a port to a dynamic aggregation group. LACP is required in this mode to communicate with a device on the other side. In this mode, the port automatically initiates LACP negotiation.

  • Passive mode: Adds a port to a dynamic aggregation group. LACP is required in this mode to communicate with a device on the other side. In this mode, a port responds only to LACP negotiation.


Note

A dynamic aggregation group can contain up to 12 ports. Out of the 12 ports, eight ports will be in the band l state and the remaining four will be in the backup state. Only ports with band l state will be allowed to forward normal traffic. If a port in the band l state faces a link down, a backup port with the highest port priority becomes the band l state.

The following is a list of the methods used to dock the devices configured in various modes:

  • A device that is configured in static mode can dock with another device that is configured in static mode.

  • A device that is configured in dynamic active mode can dock with another device that is configured either in dynamic active mode or dynamic passive mode.

  • A device that is configured with dynamic passive mode can dock with another device that is configured in dynamic active mode.

Aggregation Group ID

You can either create an aggregation ID under global configuration mode or you can add a port to an aggregation group to automatically create an aggregation ID.

Load Balance

The default mode to configure load balancing is using the source MAC address.

You can view the configuration information with the show lacp internal [ch-id ] command.

System Priority

In dynamic mode, the primary and secondary devices are selected based on the system ID, which is generated based on the configured system priority and the local MAC address. The system priority of both the devices are compared, and the device with the highest priority (lower value) is selected as the primary device. The device with the lowest priority (higher value) is selected as the secondary device. If the priority of both the devices are the same, the local MAC address is compared. The device with the lower MAC address is selected as the primary device and the device with the higher MAC address is selected as the secondary device.

The default system priority is 32768.

Port Priority

In dynamic mode, the primary device uses the logical port to forward protocol packets, such as STP, to the secomdary device. The logical port is selected based on the port ID, which is a combination of port priority and port number. The port priority of both the ports are compared, and the port with the highest priority (lower value) is selected as the logical port. If the priority of both the ports are the same, the port number is compared. The port with the lower port number is selected as the logical port.

By default, all port priorities are the same, with a value of 128. You can configure the port priorities, as required. All port priority values are configured as integer multiples of 16. For example, if the port priority value is set as 17, the actual success is issued 17 / 16 = 1.

How to Configure Port Aggregation

The following sections provide configuration information on port aggregation.

Configure Port Aggregation

To configure port aggregation, perform these procedures.

Configure an Aggregation Group ID

To configure the aggregation group ID, perform this procedure.

Before you begin

  • A port cannot be configured to multiple aggregation group IDs.

  • An aggregation group cannot be deleted until all the ports are removed from the aggregation group.

Procedure
  Command or Action Purpose
Step 1

enable

Example:
Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:
Device# configure terminal

Enters global configuration mode.

Step 3

[no] channel-group channel_group_id

Example:
Device(config)# channel-group 2

Configures the aggregation group ID.

channel_group_id : Channel group ID. The range is from 0 to 5.

Use the no channel-group channel_group_id command to disable the aggregation group ID.

Configure an Aggregation Group

To configure an aggregation group, perform this procedure.

Procedure
  Command or Action Purpose
Step 1

enable

Example:
Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:
Device# configure terminal

Enters global configuration mode.

Step 3

interface ethernet port-number

Example:
Device(config)# interface ethernet 1/1

Enters interface configuration mode.

port-number : The port ID.

Step 4

[no] channel-group channel_group_id mode {on | active | passive}

Example:
Device(config-if-ethernet-1/1)# channel-group 2 mode active

Adds a port to an aggregation group.

  • channel_group_id : Channel group ID. The range is from 0 to 5.

  • on : LACP static mode.

  • active : LACP active mode.

  • passive : LACP passive mode.

Use the no channel-group channel_group_id to remove the port from the aggregation group.

Configure a Load Balance Policy

To configure a load balance policy, perform this procedure.

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

[no]channel-group load-balance {src-mac | dst-mac | src-dst-mac | src-dst-ip | src-ip | dst-ip}

Example:

Device(config)# channel-group load-balance src-mac

Configures the load balance policy (all groups).

  • src-mac : The source MAC address. The default load balance uses the source MAC address.

  • dst-mac : The destination MAC address.

  • src-dst-mac : The source and destination MAC address.

  • src-dst-ip : The source and destination IP address.

  • src-ip : The source IP address.

  • dst-ip : The destination IP address.

Use the no channel-group load-balance command to restore the default load policy

Configure System Priority

To configure system priority, perform this procedure.

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

[no] lacp system-priority value

Example:

Device(config)# lacp system-priority

(Optional) Configures the priority of the system.

value : The priority value.

Use the no lacp system-priority command to restore the default configurations.

Configure Port Priority

To configure port priority, perform this procedure.

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

Enter your password, if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

interface ethernet port-number

Example:

Device(config)# interface ethernet 1/1

Enters interface configuration mode.

port-number : The port ID.

Step 4

[no] lacp port-priority value

Example:

Device(config-if-ethernet-1/1)# lacp port-priority 8

Configures port priority.

Use the no lacp port-priority command to restore the default priority.

Monitor Port Aggregation Configurations

Use the following commands to monitor port aggregation configurations.

Table 1. Commands to Monitor Port Aggregation Configuration Commands

Command

Purpose

show lacp internal [ch-id]

Displays the information of the aggregation group.

show lacp neighbor [ch-id]

Displays the neighbor information of the aggregation group.

show lacp sys-id

Displays the system priority configurations.

Configuration Examples: Port Aggregation

The following examples are that of a network topology where ports 1 to 12 of device 1 and device 2 are configured with dynamic LACP.

The following example shows how to configure device 1:

Device> enable
Device# configure terminal 
Device(config)# channel-group 10
Device(config)# interface range ethernet 1/1 to ethernet 1/4
Device(config-if-range)# channel-group 10 mode active

The following example shows how to configure device 2:

Device> enable
Device# configure terminal 
Device(config)# channel-group 10
Device(config)# interface range ethernet 1/1 to ethernet 1/4
Device(config-if-range)# channel-group 2 mode active

The following example shows how to view information after the dynamic LACP negotiation succeeds:

Device> enable
Device# configure terminal 
Device(config)# show lacp internal 
load balance: src-mac
Channel: 10, dynamic channel

Port   State   A-Key   O-Key   Priority   Logic-port   Actor-state
e1/1   bndl     11      11      128         1       10111100
e1/2   bndl     11      11      128         1       10111100
e1/3   bndl     11      11      128         1       10111100
e1/4   bndl     11      11      128         1       10111100