H3C S3100-52P Ethernet Switch Operation Manual-Release 1500(V1.02)

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08-Link Aggregation Operation
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Chapter 1  Link Aggregation Configuration

1.1  Overview

1.1.1  Introduction to Link Aggregation

Link aggregation means aggregating several ports together to form an aggregation group, so as to implement outgoing/incoming load sharing among the member ports in the group and to enhance the connection reliability.

Depending on different aggregation modes, link aggregation falls into three types: manual, static LACP, and dynamic LACP aggregations. Depending on whether or not load sharing is implemented, aggregation groups can be load-sharing or non-load-sharing aggregation groups.

For the member ports in an aggregation group, their basic configuration must be the same. The basic configuration includes STP, QoS, VLAN, port attributes and other associated settings.

l           STP configuration, including STP status (enabled or disabled), link attribute (point-to-point or not), STP priority, path cost, standard packet format, maximum packet transmission speed, loop prevention status, root protection status, edge port or not.

l           QoS configuration, including traffic limit, priority remarking, default 802.1p priority, bandwidth assurance, congestion avoidance, traffic redirection, traffic statistics, and so on.

l           VLAN configuration, including permitted VLANs, and default VLAN ID.

l           Port attribute configuration, including port rate, duplex mode, and link type (Trunk, Hybrid or Access). The ports for a manual or static aggregation group must have the same link type, and the ports for a dynamic aggregation group must have the same rate, duplex mode and link type.

1.1.2  Introduction to LACP

The purpose of link aggregation control protocol (LACP) is to implement dynamic link aggregation and deaggregation. This protocol is based on IEEE802.3ad and uses LACPDUs (link aggregation control protocol data unit) to interact with its peer.

After LACP is enabled on a port, LACP notifies the following information of the port to its peer by sending LACPDUs: priority and MAC address of this system, priority, number and operation key of the port. Upon receiving the information, the peer compares the information with the information of other ports on the peer device to determine the ports that can be aggregated. In this way, the two parties can reach an agreement in adding/removing the port to/from a dynamic aggregation group.

1.1.3  Operation Key

An operation key of an aggregation port is a configuration combination generated by system depending on the configurations of the port (rate, duplex mode, other basic configuration, and management key) when the port is aggregated.

1)         The selected ports in a manual/static aggregation group have the same operation key.

2)         The management key of an LACP-enabled static aggregation port is equal to its aggregation group ID.

3)         The management key of an LACP-enabled dynamic aggregation port is zero by default.

4)         The member ports in a dynamic aggregation group must have the same operation key.

1.1.4  Manual Aggregation Group

I. Introduction to manual aggregation group

A manual aggregation group is manually created. All its member ports are manually added and can be manually removed (it inhibits the system from automatically adding/removing ports to/from it). Each manual aggregation group must contain at least one port. When a manual aggregation group contains only one port, you cannot remove the port unless you remove the whole aggregation group.

LACP is disabled on the member ports of manual aggregation groups, and enabling LACP on such a port will not take effect.

II. Port status in manual aggregation group

A port in a manual aggregation group can be in one of the two states: selected or unselected. In a manual aggregation group, the selected ports can forward user service packets, but the unselected ports cannot.

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

There is a limit on the number of selected ports in an aggregation group. Therefore, if the number of the member ports serving as selected ports in an aggregation group exceeds the maximum number supported by the device, the system will choose the ports with lower port numbers as the selected ports, and set others as unselected ports.

In a manual aggregation group, the system sets the ports to selected or unselected state by the following rules:

l           The system sets the "most preferred" ports (that is, the ports take most precedence over other ports) to selected state, and others to unselected state. Port precedence descends in the following order: full duplex/high speed, full duplex/low speed, half duplex/high speed, half duplex/low speed.

l           The system sets the ports unable to aggregate with the master port (due to some hardware limit, for example, cross-board aggregation unavailability) to unselected state.

l           The system sets the ports with port attribute configuration (rate, duplex mode, and link type) different from that of the master port to unselected state.

III. Requirements on ports for manual aggregation

Generally, there is no limit on the rate and duplex mode of the ports (also including initially DOWN port) you want to add to a manual aggregation group. After aggregation, the smallest-numbered selected port is the master port of the aggregation group and the other selected ports are the member ports of the aggregation group.

 

&  Note:

For an aggregation group:

l      When the rate or duplex mode of a port in the aggregation group changes, packet loss may occur on this port;

l      When the rate of a port decreases, if the port belongs to a manual or static LACP aggregation group, the port will be switched to the unselected state; if the port belongs to a dynamic LACP aggregation group, deaggregation will occur on the port.

 

1.1.5  Static LACP Aggregation Group

I. Introduction to static LACP aggregation

A static LACP aggregation group is also manually created. All its member ports are manually added and can be manually removed (it inhibits the system from automatically adding/removing ports to/from it). Each static aggregation group must contain at least one port. When a static aggregation group contains only one port, you cannot remove the port unless you remove the whole aggregation group.

LACP is enabled on the member ports of static aggregation groups. When you remove a static aggregation group, the system will remain the member ports of the group in LACP-enabled state and re-aggregate the ports to form one or more dynamic LACP aggregation groups. You must not disable LACP on static aggregation ports.

II. Port status of static aggregation group

A port in a static aggregation group can be in one of the two states: selected or unselected. In a static aggregation group, both the selected and the unselected ports can transceive LACP protocol packets; the selected ports can transceive user service packets, but the unselected ports cannot.

 

&  Note:

In an aggregation group, the selected port with the smallest port number serves as the master port of the group, and other selected ports serve as member ports of the group.

 

In a static aggregation group, the system sets the ports to selected or unselected state by the following rules:

l           The system sets the "most preferred" ports (that is, the ports take most precedence over other ports) to selected state, and others to unselected state. Port precedence descends in the following order: full duplex/high speed, full duplex/low speed, half duplex/high speed, half duplex/low speed.

l           The system sets the state of the following ports to unselected: port connected to a peer device different from the one the master port is connected to; port connected to the same peer device as the master port but to a peer port that is not in the same aggregation group as the peer port of the master port.

l           The system sets the ports unable to aggregate with the master port (due to some hardware limit, for example, cross-board aggregation unavailability) to unselected state.

l           The system sets the ports with basic port configuration different from that of the master port to unselected state.

There is a limit on the number of selected ports in an aggregation group. Therefore, if the number of the member ports that serves as selected ports in an aggregation group exceeds the maximum number supported by the device, the system will choose the ports with lower port numbers as the selected ports, and set others as unselected ports.

1.1.6  Dynamic LACP Aggregation Group

I. Introduction to dynamic LACP aggregation group

A dynamic LACP aggregation group is automatically created and removed by the system. Users cannot add/remove ports to/from it. A port can participate in dynamic link aggregation only when it is LACP-enabled. Ports can be aggregated into a dynamic aggregation group only when they are connected to the same peer device and have the same basic configuration (such as rate and duplex mode).

Besides multiple-port aggregation groups, the system is also able to create single-port aggregation groups, each of which contains only one port. LACP is enabled on the member ports of dynamic aggregation groups.

II. Port status of dynamic aggregation group

A port in a dynamic aggregation group can be in one of the two states: selected or unselected. In a dynamic aggregation group, both the selected and the unselected ports can transceive LACP protocol packets; the selected ports can transceive user service packets, but the unselected ports cannot.

 

&  Note:

In an aggregation group, the selected port with the smallest port number serves as the master port of the group, and other selected ports serve as member ports of the group.

 

There is a limit on the number of selected ports in an aggregation group. Therefore, if the number of the member ports that can be set as selected ports in an aggregation group exceeds the maximum number supported by the device, the system will negotiate with its peer end, to determine the states of the member ports according to the port IDs of the preferred device (that is, the device with smaller system ID). The following is the negotiation procedure:

1)         Compare device IDs (system priority + system MAC address) between the two parties. First compare the two system priorities, then the two system MAC addresses if the system priorities are equal. The device with smaller device ID will be considered as the preferred one.

2)         Compare port IDs (port priority + port number) on the preferred device. The comparison between two port IDs is as follows: First compare the two port priorities, then the two port numbers if the two port priorities are equal; the port with the smallest port ID is the selected port and the left ports are unselected ports.

III. Configuring system priority

LACP determines the selected and unselected states of the dynamic aggregation group members according to the priority of the port ID on the end with the preferred device ID.

The device ID consists of two-byte system priority and six-byte system MAC address, that is, device ID = system priority + system MAC address.

When two device IDs are compared, the system priorities are compared first, and the system MAC addresses are compared when the system priorities are the same. The device with smaller device ID will be considered as the preferred one.

 

&  Note:

Changing the system priority of a device may change the preferred device between the two parties, and may further change the states (selected or unselected) of the member ports of dynamic aggregation groups.

 

IV. Configuring port priority

LACP determines the selected and unselected states of the dynamic aggregation group members according to the port IDs on the device with the preferred device ID. When the number of members in an aggregation group exceeds the number of selected ports supported by the device in each group, LACP determines the selected and unselected states of the ports according to the port IDs. The ports with superior port IDs will be set to selected state and the ports with inferior port IDs will be set to unselected state.

The port ID consists of two-byte port priority and two-byte port number, that is, port ID = port priority + port number. When two port IDs are compared, the port priorities are compared first, and the port numbers are compared if the port priorities are the same. The port with smaller port ID is considered as the preferred one.

1.1.7  Aggregation Group Categories

Depending on whether or not load sharing is implemented, aggregation groups can be load-sharing or non-load-sharing aggregation groups. When load sharing is implemented,

l           For IP packets, the system will implement load-sharing based on source IP address and destination IP address;

l           For non-IP packets, the system will implement load-sharing based on source MAC address and destination MAC address.

In general, the system only provides limited load-sharing aggregation resources (currently N/2 load-sharing aggregation groups can be created at most, N is the number of ports), so the system needs to reasonably allocate the resources among different aggregation groups.

The system always allocates hardware aggregation resources to the aggregation groups with higher priorities. When load-sharing aggregation resources are used up by existing aggregation groups, newly-created aggregation groups will be non-load-sharing ones.

Load-sharing aggregation resources are allocated to aggregation groups in the following order:

l           An aggregation group containing special ports (such as 10GE port) which require hardware aggregation resources has higher priority than any aggregation group containing no special port.

l           A manual or static aggregation group has higher priority than a dynamic aggregation group (unless the latter contains special ports while the former does not).

l           For aggregation groups, the one that might gain higher speed if resources were allocated to it has higher priority than others. If the groups can gain the same speed, the one with smallest master port number has higher priority than other groups.

When an aggregation group of higher priority appears, the aggregation groups of lower priorities release their hardware resources. For single-port aggregation groups, they can transceive packets normally without occupying aggregation resources

 

  Caution:

A load-sharing aggregation group contains at least two selected ports, but a non-load-sharing aggregation group can only have one selected port at most, while others are unselected ports.

 

1.2  Link Aggregation Configuration

 

  Caution:

l      The commands of link aggregation cannot be configured with the commands of port loopback detection feature at the same time.

l      The ports where the mac-address max-mac-count command is configured cannot be added to an aggregation group. Contrarily, the mac-address max-mac-count command cannot be configured on a port that has already been added to an aggregation group.

l      MAC-authentication-enabled ports and 802.1x-enabled ports cannot be added to an aggregation group.

l      Mirroring destination ports and mirroring reflector ports cannot be added to an aggregation group.

l      Ports configured with blackhole MAC addresses, static MAC addresses or the static ARP protocol cannot be added to the aggregation group.

l      Ports where the IP-MAC address binding is configured cannot be added to an aggregation group.

l      Port-security-enabled ports cannot be added to an aggregation group.

 

1.2.1  Configuring a Manual Aggregation Group

You can create a manual aggregation group, or remove an existing manual aggregation group (after that, all the member ports in the group are removed from the ports).

For a manual aggregation group, a port can only be manually added/removed to/from the manual aggregation group.

Table 1-1 Configure a manual aggregation group

Operation

Command

Description

Enter system view

system-view

Create a manual aggregation group

link-aggregation group agg-id mode manual

Required

Configure a description for the aggregation group

link-aggregation group agg-id description agg-name

Optional

By default, an aggregation group has no description.

Enter Ethernet port view

interface interface-type interface-number

Add the Ethernet port to the aggregation group

port link-aggregation group agg-id

Required

 

Note that:

1)         When creating an aggregation group:

l           If the aggregation group you are creating already exists but contains no port, its type will change to the type you set.

l           If the aggregation group you are creating already exists and contains ports, the possible type changes may be: changing from dynamic or static to manual, and changing from dynamic to static; and no other kinds of type change can occur.

l           When you change a dynamic/static group to a manual group, the system will automatically disable LACP on the member ports. When you change a dynamic group to a static group, the system will remain the member ports LACP-enabled.

2)         When a manual or static aggregation group contains only one port, you cannot remove the port unless you remove the whole aggregation group.

1.2.2  Configuring a Static LACP Aggregation Group

You can create a static LACP aggregation group, or remove an existing static aggregation group (after that, the system will re-aggregate the original member ports in the group to form one or more dynamic aggregation groups.).

For a static aggregation group, a port can only be manually added/removed to/from the static aggregation group.

 

&  Note:

When you add an LACP-enabled port to a manual aggregation group, the system will automatically disable LACP on the port. Similarly, when you add an LACP-disabled port to a static aggregation group, the system will automatically enable LACP on the port.

 

Table 1-2 Configure a static LACP aggregation group

Operation

Command

Description

Enter system view

system-view

Create a static aggregation group

link-aggregation group agg-id mode static

Required

Configure a description for the aggregation group

link-aggregation group agg-id description agg-name

Optional

By default, an aggregation group has no description.

Enter Ethernet port view

interface interface-type interface-number

Add the port to the aggregation group

port link-aggregation group agg-id

Required

 

&  Note:

For a static LACP aggregation group or a manual aggregation group, you are recommended not to cross cables between the two devices at the two ends of the aggregation group. For example, suppose port 1 of the local device is connected to port 2 of the peer device. To avoid cross-connecting cables, do not connect port 2 of the local device to port 1 of the peer device. Otherwise, packets may be lost.

 

1.2.3  Configuring a Dynamic LACP Aggregation Group

A dynamic LACP aggregation group is automatically created by the system based on LACP-enabled ports. The adding and removing of ports to/from a dynamic aggregation group are automatically accomplished by LACP.

You need to enable LACP on the ports which you want to participate in dynamic aggregation of the system, because, only when LACP is enabled on those ports at both ends, can the two parties reach agreement in adding/removing ports to/from dynamic aggregation groups.

 

&  Note:

You cannot enable LACP on a port which is already in a manual aggregation group.

 

Table 1-3 Configure a dynamic LACP aggregation group

Operation

Command

Description

Enter system view

system-view

Configure a description for an aggregation group

link-aggregation group agg-id description agg-name

Optional

By default, an aggregation group has no description.

Configure the system priority

lacp system-priority system-priority

Optional

By default, the system priority is 32,768.

Enter Ethernet port view

interface interface-type interface-number

Enable LACP on the port

lacp enable

Required

By default, LACP is disabled on a port.

Configure the port priority

lacp port-priority port-priority

Optional

By default, the port priority is 32,768.

 

1.3  Displaying and Maintaining Link Aggregation Configuration

After the above configuration, execute the display command in any view to display the running status after the link aggregation configuration and verify your configuration. Execute the reset command in user view to clear LACP statistics on ports.

Table 1-4 Display and maintain link aggregation configuration

Operation

Command

Description

Display summary information of all aggregation groups

display link-aggregation summary

You can execute the display command in any view.

Display detailed information of a specific aggregation group or all aggregation groups

display link-aggregation verbose [ agg-id ]

Display link aggregation details of a specified port or port range

display link-aggregation interface interface-type interface-number [ to interface-type interface-number ]

Display local device ID

display lacp system-id

Clear LACP statistics about a specified port or port range

reset lacp statistics [ interface interface-type interface-number [ to interface-type interface-number ] ]

Execute the reset command in user view.

 

1.4  Link Aggregation Configuration Example

I. Network requirements

l           Switch A connects to Switch B with three ports Ethernet1/0/1 to Ethernet1/0/3. It is required that incoming/outgoing load between the two switches can be shared among the three ports.

l           Adopt three different aggregation modes to implement link aggregation on the three ports between switch A and B.

II. Network diagram

Figure 1-1 Network diagram for link aggregation configuration

III. Configuration procedure

The following only lists the configuration on Switch A; you must perform the similar configuration on Switch B to implement link aggregation.

1)         Adopting manual aggregation mode

# Create manual aggregation group 1.

<H3C> system-view

[H3C] link-aggregation group 1 mode manual

# Add Ethernet1/0/1 through Ethernet1/0/3 to aggregation group 1.

[H3C] interface Ethernet1/0/1

[H3C-Ethernet1/0/1] port link-aggregation group 1

[H3C-Ethernet1/0/1] interface Ethernet1/0/2

[H3C-Ethernet1/0/2] port link-aggregation group 1

[H3C-Ethernet1/0/2] interface Ethernet1/0/3

[H3C-Ethernet1/0/3] port link-aggregation group 1

2)         Adopting static LACP aggregation mode

# Create static aggregation group 1.

<H3C> system-view

[H3C] link-aggregation group 1 mode static

# Add Ethernet1/0/1 through Ethernet1/0/3 to aggregation group 1.

[H3C] interface Ethernet1/0/1

[H3C-Ethernet1/0/1] port link-aggregation group 1

[H3C-Ethernet1/0/1] interface Ethernet1/0/2

[H3C-Ethernet1/0/2] port link-aggregation group 1

[H3C-Ethernet1/0/2] interface Ethernet1/0/3

[H3C-Ethernet1/0/3] port link-aggregation group 1

3)         Adopting dynamic LACP aggregation mode

# Enable LACP on Ethernet1/0/1 through Ethernet1/0/3.

<H3C> system-view

[H3C] interface Ethernet1/0/1

[H3C-Ethernet1/0/1] lacp enable

[H3C-Ethernet1/0/1] interface Ethernet1/0/2

[H3C-Ethernet1/0/2] lacp enable

[H3C-Ethernet1/0/2] interface Ethernet1/0/3

[H3C-Ethernet1/0/3] lacp enable

Note that, the three LACP-enabled ports can be aggregated into a dynamic aggregation group to implement load sharing only when they have the same basic configuration (such as rate and duplex mode and so on).