LACP
Definition
LACP was developed based on IEEE 802.1AX. LACP dynamically aggregates and
deaggregates Ethernet links using the following functions:
-
Enables the data switching device to use a standard negotiation mode for link
aggregation.
After LACP is enabled, the access device aggregates multiple links according
to its configuration and enables the aggregation link to transmit and receive
data.
Member ports in a LAG send LACP packets to notify the peer device of the
information, including the system priority, system MAC address, port priority,
port ID, and administrative key.
After receiving the information, the peer device compares the information
with the one saved on other ports to select ports that can be aggregated. The
interconnected devices reach agreement on the ports that can transmit and
receive data and determine which links carry traffic.
The LACP packets are sent in any of the following modes:
- Event-triggered transmission
A change in the state of the local device or in the local configuration
triggers the generation and transmission of a new LACP packet.
- Periodic transmission
When an aggregation link is stable, the system state is periodically
exchanged to maintain the aggregation link.
-
Maintains the aggregation link by periodically exchanging the system state
when the link is stable.
After aggregation links are generated, LACP maintains link status. When the
aggregation condition changes, LACP automatically adjusts the link aggregation.
The aggregation condition changes if one or more of the following occurs:
- Physical port status changes.
- Board status changes.
- Results negotiated with the peer end are changed.
LACP was developed based on IEEE 802.1AX. LACP dynamically aggregates and
deaggregates Ethernet links using the following functions:
-
Enables the data switching device to use a standard negotiation mode for link
aggregation.
After LACP is enabled, the access device aggregates multiple links according to its configuration and enables the aggregation link to transmit and receive data.
Member ports in a LAG send LACP packets to notify the peer device of the information, including the system priority, system MAC address, port priority, port ID, and administrative key.
After receiving the information, the peer device compares the information with the one saved on other ports to select ports that can be aggregated. The interconnected devices reach agreement on the ports that can transmit and receive data and determine which links carry traffic.
The LACP packets are sent in any of the following modes:- Event-triggered transmission
A change in the state of the local device or in the local configuration
triggers the generation and transmission of a new LACP packet.
- Periodic transmission When an aggregation link is stable, the system state is periodically exchanged to maintain the aggregation link.
- Event-triggered transmission
A change in the state of the local device or in the local configuration
triggers the generation and transmission of a new LACP packet.
-
Maintains the aggregation link by periodically exchanging the system state
when the link is stable.
After aggregation links are generated, LACP maintains link status. When the aggregation condition changes, LACP automatically adjusts the link aggregation. The aggregation condition changes if one or more of the following occurs:
- Physical port status changes.
- Board status changes.
- Results negotiated with the peer end are changed.
LACP Priority
LACP priority includes system priority and port priority. Priority setting
allows negotiation of aggregation information between LAGs at two ends and
real-time maintenance on link status.
Priority Type
Function
Description
System priority
Specifies the priority of a LAG on the device.
Determines which party in the interconnected devices is dominant in protocol
negotiation. A device with a higher priority is dominant in LACP protocol
negotiation, and the information provided by it prevails for such operations as
selection of an active port.
NOTE:
If interconnected devices have the same system priority,
compare the system MAC addresses. The device with a smaller MAC address is
dominant in LACP protocol negotiation.
Port priority
Specifies the priority of a port in a LAG.
Specifies the active ports in a LAG that will carry services with preference.
Active ports in a LAG can be adjusted based on port priorities.
NOTE:
In a LAG, if two ports have the same priority, the port with
smaller subrack ID, slot ID, and port ID (frameid/slotid/portid) is
preferentially selected as the active
one.
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NOTE:
System priority and port priority work together to determine
which ports in a LAG are used to carry services with preference. System priority
prevails over port priority.
| Priority Type | Function | Description |
|---|---|---|
| System priority | Specifies the priority of a LAG on the device. |
Determines which party in the interconnected devices is dominant in protocol
negotiation. A device with a higher priority is dominant in LACP protocol
negotiation, and the information provided by it prevails for such operations as
selection of an active port.
NOTE:
If interconnected devices have the same system priority,
compare the system MAC addresses. The device with a smaller MAC address is
dominant in LACP protocol negotiation.
|
| Port priority | Specifies the priority of a port in a LAG. |
Specifies the active ports in a LAG that will carry services with preference.
Active ports in a LAG can be adjusted based on port priorities.
NOTE:
In a LAG, if two ports have the same priority, the port with
smaller subrack ID, slot ID, and port ID (frameid/slotid/portid) is
preferentially selected as the active
one.
|
System priority and port priority work together to determine
which ports in a LAG are used to carry services with preference. System priority
prevails over port priority.
Timeout Time for Exchanging LACP Packets
The access device periodically sends and receives LACP packets to prevent
information loss. If the device does not receive any LACP packets within three
LACP packet exchanging periods, the device determines that the port is faulty.
To ensure detection sensitivity, LACP defines long timeout and short timeout.
The device uses short time for exchanging LACP packets by default except that
the peer device requires long timeout.
According to LACP, the short timeout time is 1s, and the long
timeout time is 30s. Huawei access devices support the following timeout time:
- Short timeout: 1-10s
- Long timeout: 20-40s
To ensure detection sensitivity, LACP defines long timeout and short timeout.
The device uses short time for exchanging LACP packets by default except that the peer device requires long timeout.
According to LACP, the short timeout time is 1s, and the long
timeout time is 30s. Huawei access devices support the following timeout time:
- Short timeout: 1-10s
- Long timeout: 20-40s
LACP Applications
Huawei access devices use LACP to implement link aggregation. Specifically,
after an LACP LAG is configured, the access device negotiates with its peer end
about aggregation information. For details about LACP applications, see "LACP
Aggregation" in LAG Type.
Parent topic: Basic Concepts of Ethernet Link
Aggregation
More related:
Huawei access devices use LACP to implement link aggregation. Specifically,
after an LACP LAG is configured, the access device negotiates with its peer end
about aggregation information. For details about LACP applications, see "LACP
Aggregation" in LAG Type.
Parent topic: Basic Concepts of Ethernet Link
Aggregation
More related:
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