Table of Contents

Chapter 1 Link Aggregation Overview.. 1-1

1.1 Link Aggregation. 1-1

1.1.1 LACP. 1-1

1.1.2 Consistency Considerations for Ports in an Aggregation. 1-1

1.2 Approaches to Link Aggregation. 1-3

1.2.1 Manual Link Aggregation. 1-3

1.2.2 Static LACP link aggregation. 1-4

1.3 Load Sharing in a Link Aggregation Group. 1-5

1.4 Aggregation Port Group. 1-6

Chapter 2 Link Aggregation Configuration. 2-1

2.1 Configuring Link Aggregation. 2-1

2.1.1 Configuring a Manual Link Aggregation Group. 2-1

2.1.2 Configuring a Static LACP Link Aggregation Group. 2-2

2.1.3 Configuring an Aggregation Group Name. 2-3

2.1.4 Entering Aggregation Port Group View. 2-3

2.2 Displaying and Maintaining Link Aggregation. 2-4

2.3 Link Aggregation Configuration Example. 2-4

 

Chapter 1  Link Aggregation Overview

This chapter covers these topics:

l           Link Aggregation

l           Approaches to Link Aggregation

l           Load Sharing in a Link Aggregation Group

l           Aggregation Port Group

1.1  Link Aggregation

Link aggregation allows you to increase bandwidth by distributing traffic on the member ports in an aggregation group. In addition, it provides reliable connectivity because these member ports can dynamically back up each other.

1.1.1  LACP

Link Aggregation Control Protocol (LACP) is defined in IEEE 802.3ad. Link aggregation control protocol data unit (LACPDU) is used for exchanging information among LACP-enabled devices.

After LACP is enabled on a port, the port sends LACPDUs to notify the remote system of its system LACP priority, system MAC address, port LACP priority, port number, and operational key. Upon receipt of an LACPDU, the remote system compares the received information with the information received on other ports to determine the ports that can operate as selected ports. This allows the two systems to reach agreement on the states of the related ports

When aggregating ports, link aggregation control automatically assigns each port an operational key based on its rate, duplex mode, and other basic configurations. In an LACP aggregation group, all ports share the same operational key; in a manual or static LACP aggregation, the selected ports share the same operational key.

1.1.2  Consistency Considerations for Ports in an Aggregation

To participate in traffic sharing, member ports in an aggregation group must use the same configurations with respect to STP, QoS, GVRP, Q-in-Q, BPDU tunnel, VLAN, port attributes, MAC address learning, and so on as shown in the following table.

Table 1-1 Consistency considerations for ports in an aggregation

Category	Considerations
STP	State of port-level STP (enabled or disabled) Attribute of the link (point-to-point or otherwise) connected to the port Port path cost STP priority Maximum transmission rate Loop protection Root protection Port type (whether the port is an edge port)
QoS	Traffic policing Port rate limiting Strict priority (SP) queuing Weighted round robin (WRR) queuing Port priority Policy setting on the port Port trust mode
GVRP	GVRP state on ports (enabled or disabled) GVRP registration type GARP timers
Q-in-Q	State of Q-in-Q (enabled or disabled) Added outer VLAN tag Policy of appending outer VLAN tag according to inner VLAN IDs
BPDU tunnel	BPDU tunnel state on ports (enabled or disabled) BPDU tunnel state for STP on ports (enabled or disabled)
VLAN	VLANs carried on the port Default VLAN ID on the port Link type of the port, which can be trunk, hybrid, or access VLAN tag configuration
Port attribute	Port rate Duplex mode Up/down state of the link Isolation group membership of the port
MAC address learning	Maximum number of MAC addresses that can be learned on the port

 

1.2  Approaches to Link Aggregation

Two ways are available for implementing link aggregation, as described in Manual Link Aggregation and Static LACP link aggregation.

1.2.1  Manual Link Aggregation

I. Overview

Manual aggregations are created manually. Member ports in a manual aggregation are LACP-disabled.

II. Port states in a manual aggregation

In a manual aggregation group, ports are either selected or unselected. Selected ports can receive and transmit data frames whereas unselected ones cannot.

When setting the state of ports in a manual aggregation group, the system considers the following:

l           The system selects the port with the highest priority in the up state as the reference port of the aggregation group. Port priority descends in the following order: full duplex/high speed, full duplex/low speed, half duplex/high speed, and half duplex/low speed. If multiple ports are of the same priority, the one with the lowest port number is the reference port.

l           Ports in the up state with the same speed, duplex mode, link state, and basic configuration as the reference port become the candidates for selected ports, while the other ports become unselected ports.

l           There is a limit on the number of selected ports in a manual aggregation group. If the number of selected-port candidates does not reach the limit, all the candidates become selected ports; if the number of candidates exceeds the limit, the candidates with lower port numbers become selected ports, while the other candidates become unselected ports.

l           The selected port with the lowest port number serves as the master port of the aggregation group, and the other ports serve as the member ports of the aggregation group.

l           If all the ports of an aggregations port are down, the port with the lowest port number is the master port. In this case, all of them are unselected ports.

In addition, unless the master port should be selected, a port that joins the group after the limit is reached will not be placed in selected state even if it should be in normal cases. This is to prevent the ongoing service on selected ports from being interrupted. You need to avoid the situation however as the selected/unselected state of a port may become different after a reboot.

III. Port Configuration Considerations in manual aggregation

As mentioned above, in a manual aggregation group, only ports with configurations consistent with those of the reference port can become selected. These configurations include port rate, duplex mode, link state, and other basic configurations, as described in Consistency Considerations for Ports in an Aggregation.

You need to maintain the basic configurations of these ports manually to ensure consistency. As one configuration change may involve multiple ports, this can become troublesome if you need to do that port by port. As a solution, you may add the ports into an aggregation port group where you can make configuration for all member ports.

When the configuration of some port in a manual aggregation group changes, the system does not remove the aggregation; instead, it re-sets the selected/unselected state of the member ports and re-selects a master port.

1.2.2  Static LACP link aggregation

I. Overview

Static aggregations are created manually. After you add a port to a static aggregation, LACP is enabled on it automatically.

II. Port states in static aggregation

In a static aggregation group, ports can be selected or unselected, where both can receive and transmit LACPDUs but only selected ports can receive and transmit data frames.

When setting the state of the ports in the local and remote static aggregation groups, the local and remote systems do the following:

1)         Compare their system IDs to identify the higher priority system. (The system ID comprises LACP priority and system MAC address.)

l           First compare the system LACP priorities. The system with lower system LACP priority wins out.

l           If the system LACP priorities are the same, compare the system MAC addresses. The system with the smaller MAC address wins out.

2)         Compare the port IDs on the higher priority system. (The port ID comprises port LACP priority and port number.)

l           Compare the port LACP priorities. The port with lower port LACP priority wins out.

l           If two ports with the same port LACP priority are present, compare their port numbers. The one with the smaller port ID wins out to become the reference port.

3)         Select the candidates for selected ports. To be a candidate, a port must be in the up state with the same speed, duplex mode, link state, and basic configuration as the reference port; in addition, their peer ports on the other system must have the same configuration. All the ports but the selected-port candidates become unselected.

4)         As there is a limit on the number of selected ports, not all selected-port candidates can become selected ports. Before the limit is reached, all the candidates are set to the selected state. When the limit is reached, the candidates with lower port numbers are set to the selected state while the other candidates are set to the unselected state. At the same time, the other system gets aware of the state change of the ports on the higher priority system and thus sets the state of the corresponding local ports.

5)         Set the selected port with the lowest port number as the master port in the aggregation group on each system.

III. Port configuration considerations in static aggregation

Like in a manual aggregation group, in a static LACP aggregation group, only ports with configurations consistent with those of the reference port can become selected. These configurations include port rate, duplex mode, link state and other basic configurations described in Consistency Considerations for Ports in an Aggregation.

You need to maintain the basic configurations of these ports manually to ensure consistency. As one configuration change may involve multiple ports, this can become troublesome if you need to do that port by port. As a solution, you may add the ports into an aggregation port group where you can make configuration for all member ports.

When the configuration of some port in a static aggregation group changes, the system does not remove the aggregation; instead, it re-sets the selected/unselected state of the member ports and re-selects a master port.

1.3  Load Sharing in a Link Aggregation Group

Link aggregation groups fall into load sharing aggregation groups and non-load sharing aggregation groups depending on their support to load sharing.

A load sharing aggregation group can contain at least one selected port but a non-load sharing aggregation group can contain only one.

Link aggregation groups perform load sharing depending on availability of hardware resources. When hardware resources are available, link aggregation groups created containing at least two selected ports perform load sharing, while link aggregation groups created with only one selected port does not perform load sharing. After hardware resources become depleted, link aggregation groups created work in non-load sharing mode.

Load sharing is implemented through the selected ports in an aggregation group. However, the way of selecting forwarding ports varies by packet type:

l           For a Layer-2 unicast packet with a known destination MAC address, if the packet carries an IP datagram, the switch selects the forwarding port according to the source IP address and destination IP address; otherwise, the switch selects the forwarding port according to the source MAC address and destination MAC address.

l           For a unicast IP packet with a known destination IP address, the switch selects the forwarding port according to the source IP address and the destination IP address of the packet.

l           For a Layer-2 multicast packet with a known destination MAC address, the switch selects the forwarding port according to the source MAC address, the destination MAC address, and the receiving port of the packet.

l           For a Layer-3 multicast packet with a known IP address, the switch selects the forwarding port according to the source IP address, the destination IP address, and the receiving port of the packet.

l           For an unknown unicast/multicast/broadcast packet, the switch selects the forwarding port according to the source MAC address, the destination MAC address, and the receiving port of the packet.

 

 

1.4  Aggregation Port Group

As mentioned earlier, in a manual or static aggregation group, a port can be selected only when its configuration is the same as that of the reference port in terms of duplex/speed pair, link state, and other basic configurations. Their configuration consistency requires administrative maintenance, which is troublesome after you change some configuration.

To simplify configuration, port-groups are provided allowing you to configure for all ports in individual groups at one time. One example of port-groups is aggregation port group.

Upon creation or removal of a link aggregation group, an aggregation port-group which cannot be administratively created or removed is automatically created or removed. In addition, you can only assign/remove a member port to/from an aggregation port-group by assigning/removing it from the corresponding link aggregation group.

For more information about port-groups, refer to Port Correlation Configuration.

 

Chapter 2  Link Aggregation Configuration

When configuring link aggregation, go to these sections for information you are interested in:

l           Configuring Link Aggregation

l           Displaying and Maintaining Link Aggregation

l           Link Aggregation Configuration Example

2.1  Configuring Link Aggregation

This section covers these topics:

l           Configuring a Manual Link Aggregation Group

l           Configuring a Static LACP Link Aggregation Group

l           Configuring an Aggregation Group Name

l           Entering Aggregation Port Group View

2.1.1  Configuring a Manual Link Aggregation Group

Follow these steps to create a manual aggregation group and add an Ethernet port to it:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Create a manual aggregation group	link-aggregation group agg-id mode manual	Required
Enter Ethernet port view	interface interface-type interface-number	––
Assign the Ethernet port to the aggregation group	port link-aggregation group agg-id	Required

 

Note that:

l           You can create a manual aggregation group by changing the type of an existing static aggregation group. When you create a manual aggregation group in this way and the static aggregation group contains ports, LACP is disabled on the ports after the manual aggregation group is created.

l           An aggregation group cannot contain the following ports: ports configured with static MAC addresses or black hole MAC addresses, voice VLAN-enabled ports, or 802.1x-enabled ports. 

l           After you remove a manual aggregation group, all the ports in the group are dismissed from it.

l           For a manual aggregation group containing only one port, the only way to remove the port from it is to remove the aggregation group.

l           To make an aggregation group to function properly, make sure the selected states of the ports on the both sides of the same link are the same.

2.1.2  Configuring a Static LACP Link Aggregation Group

Follow these steps to configure a static aggregation group:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Configure the system LACP priority	lacp system-priority system-priority	Optional 32768 by default. Changing system LACP priority can affect the selected/unselected state of the ports in the group.
Create a static LACP aggregation group	link-aggregation group agg-id mode static	Required
Enter Ethernet port view	interface interface-type interface-number	––
Configure the port LACP priority	lacp port-priority port-priority	Optional 32768 by default. Changing port LACP priority can affect the selected/unselected state of the ports in the group.
Assign the Ethernet port to the aggregation group	port link-aggregation group agg-id	Required

 

Note that:

l           You can create a static aggregation group by changing the type of an existing manual link aggregation group that contains no port.

l           An aggregation group cannot contain the following ports: ports configured with static MAC addresses or black hole MAC addresses, voice VLAN-enabled ports, or 802.1x-enabled ports. 

l           After you remove a static aggregation group, all the ports in the group are dismissed from it, and LACP is disabled on the ports.

l           For a static LACP aggregation group containing only one port, the only way to remove the port from the aggregation group is to remove the aggregation group.

 

 

2.1.3  Configuring an Aggregation Group Name

Follow these steps to configure a name for an aggregation group:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Configure a name for a link aggregation group	link-aggregation group agg-id description agg-name	Required None is configured by default.

 

2.1.4  Entering Aggregation Port Group View

In aggregation port group view, you can make configuration for all the member ports in a link aggregation group at one time.

Follow these steps to enter aggregation port group view:

To do…	Use the command…	Remarks
Enter system view	system-view	––
Enter aggregation port group view	port-group aggregation agg-id	––

 

 

2.2  Displaying and Maintaining Link Aggregation

To do…	Use the command…	Remarks
Display the local system ID	display lacp system-id	Available in any view
Display detailed information about link aggregation for the specified port or ports	display link-aggregation interface interface-type interface-number [ to interface-type interface-number ]	Available in any view
Display summaries for all link aggregation groups	display link-aggregation summary	Available in any view
Display detailed information about specified or all link aggregation groups	display link-aggregation verbose [ agg-id ]	Available in any view
Clear the statistics about LACP for specified or all ports	reset lacp statistics [ interface interface-type interface-number [ to interface-type interface-number ] ]	Available in user view

 

2.3  Link Aggregation Configuration Example

I. Network requirements

l           Switch A aggregates ports GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to form one link connected to Switch B and performs load sharing among these ports.

l           Create a tunnel service-loop group and add port GigabitEthernet 1/0/1 to the group.

II. Network diagram

Figure 2-1 Network diagram for link aggregation configuration

III. Configuration procedure

 

 

1)         In manual aggregation approach

# Create manual aggregation group 1.

<SwitchA> system-view

[SwitchA] link-aggregation group 1 mode manual

# Add ports GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the group.

[SwitchA] interface GigabitEthernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] port link-aggregation group 1

[SwitchA-GigabitEthernet1/0/1] interface GigabitEthernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] port link-aggregation group 1

[SwitchA-GigabitEthernet1/0/2] interface GigabitEthernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] port link-aggregation group 1

2)         In static aggregation approach

# Create static aggregation group 1.

<SwitchA> system-view

[SwitchA] link-aggregation group 1 mode static

# Add ports GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the group.

[SwitchA] interface GigabitEthernet 1/0/1

[SwitchA-GigabitEthernet1/0/1] port link-aggregation group 1

[SwitchA-GigabitEthernet1/0/1] interface GigabitEthernet 1/0/2

[SwitchA-GigabitEthernet1/0/2] port link-aggregation group 1

[SwitchA-GigabitEthernet1/0/2] interface GigabitEthernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] port link-aggregation group 1