Configuring Dual-homed Inter-Board Link Aggregation

In dual-homed inter-board link aggregation, primary and secondary upper-layer devices are configured. LAGs are configured on these two devices for interconnecting with the access device
(such as Huawei MA5683T). This type of link aggregation provides protection for upper-layer devices between LAGs. If the active LAG malfunctions, the bandwidth and priority of the active LAG are lower than those of the standby LAG, which triggers a protection switchover.

Service Requirements

The bandwidth between the access device uplink ports and the upper-layer switch(such as S5720-36C-PWR-EI-AC) is required to increase in load sharing mode. In addition, link protection is required. If one link becomes faulty, the upstream bandwidth is decreased, and the Internet access rate is reduced. However, the Internet access service must not be interrupted, and the access rate reduction slightly degrades user experience.
LAG protection must be implemented. If one LAG becomes faulty, services are not interrupted.

In upstream transmission(such as OSN3500) of inter-board link aggregation scenarios, the access device functions as the actor (indicating the party that is dominant in negotiation) to determine the primary and secondary roles of LAGs. To determine the primary device, the access device adheres to the following rules:

• The access device uses the received peer end's information carried in the LACP packet to determine the dual homing network. Then, the access device automatically calculates the number of LinkUp ports on the two upper-layer devices, and selects the device that has the greater number of LinkUp ports as the primary device. The other upper-layer device is the secondary device.
• If the two upper-layer devices provide the same number of LinkUp ports, the rules vary depending on the LACP priority preemption mode configured on the access device.
  • If LACP works in priority preemption mode, the access device preferentially selects the peer end device connected to the local port with the higher priority as the primary device.
  • If LACP works in non-priority preemption mode, the access device preferentially selects the peer end device connected to the port that is currently in forwarding state as the primary device.
• If the link forwarding traffic is interrupted, the access device uses the preceding rules to select the primary device.

Networking

dual-homed inter-board link aggregation: Two GIU boards on the access device are used for upstream transmission, and the access device is interconnected with two devices. One LAG is configured for a GIU board of the access device and an interconnected device.

Figure 1 Networking of dual-homed inter-board link aggregation

Prerequisite

• Interconnected devices, hardware, and ports support LAGs.
• The two aggregated ports do not have a static MAC address. To check whether an aggregated port has a static MAC address, run the display mac-address command.

Data Plan

Table 1 lists data plan for configuring dual-homed inter-board link aggregation.

Table 1 Data plan for configuring dual-homed inter-board link aggregation

Item	Data	Remarks
LAG member port	0/19/0 (master port) 0/19/1 0/20/0 0/20/1	The configuration of the slave port must be the same as that of the master device. Alternatively, the slave port is not configured. It is recommended that you do not configure the slave port to prevent a service failure due to data inconsistency with the master port.
Aggregation type	LACP aggregation	When the access device connects to a device supporting LACP, the LACP aggregation mode is recommended. When the access device connects to a device not supporting LACP, only manual aggregation can be configured.
Load sharing type	Load sharing	A LAG works in load sharing mode by default.

Procedure

1. (Mandatory) Create a LAG and select an aggregation type. Run the link-aggregation command to add multiple uplink Ethernet ports to the same LAG to protect ports and share load between the ports. The port with the smallest port ID is the master port.
   
2. (Optional) Add a LAG member port. Perform this step when the LAG bandwidth or link reliability is required to improve. To do so, run the link-aggregation add-member command to add an Ethernet port to a LAG.
   
   NOTE:

   When adding a port to or deleting a port from a LAG, if this port has connected to the peer device, run the shutdown(Ethernet) command to deactivate this port or disconnect the optical fiber from this port to prevent a link loop.
   
   
3. (Optional) Select a load bearing type. This step is required only when the LAG works in LACP aggregation mode.
   Configuring the maximum active links in a LAG implements traffic allocation in load non-sharing mode. For example, M+N links have been configured in a LAG. Then, run the link-aggregation max-link-number command to specify N active links. The remaining M links are standby ones. If an active link is interrupted, a standby link automatically changes to the active one.
   
   
4. (Optional) Set the system priority and port priority. This step is required only when the LAG works in LACP aggregation mode.
   
   • LACP system priority: If the access device is dual homed to two convergence devices, the access device determines the primary and standby LAGs. Run the lacp priority system command to set the LACP system priority of the access device to be higher than that of the peer device.
   • LACP port priority: LACP port priority must be used with the maximum number of links. If a port is required preferentially for carrying services, set its priority higher. Run the lacp priority port command to change the link priority so that the standby link and the active link can be switched over.
   
   
5. (Optional) Select a link revertive mode. This step is required only when the LAG works in LACP aggregation mode. Run the lacp preempt command to set whether traffic is switched back to the original link when the original link recovers.
   
6. (Optional) Query LAG information. Run the display link-aggregation command to query the LAG information, including the master port, number of links, aggregation type (manual or LACP aggregation), and maximum number of links.
   

Result

The bandwidth between the access device uplink ports and the upper-layer switch is increased in load sharing mode. In addition, link protection is implemented. If one LAG becomes faulty, services are not interrupted. If this happens, the access device automatically switches services to the LAG providing a higher bandwidth.

Example

The following configurations are used as an example to configure dual-homed inter-board link aggregation:

• The access device transmits data upstream using two GIU boards.
• Uplink ports 0/19/0, 0/20/0, 0/19/1, and 0/20/1 on the active and standby GIU boards are added to an inter-board LAG.
• Packets are forwarded to these ports based on source and destination MAC addresses.
• The LAG works in LACP aggregation mode.

huawei(config)#link-aggregation 0/19 0-1 0/20 0-1 egress-ingress workmode lacp-static
huawei(config)#display link-aggregation all
  -------------------------------------------------------------------------
  Master port  Link aggregation mode  Port NUM  Work mode  Max link number
  -------------------------------------------------------------------------
  0/19/0       egress-ingress                4  lacp-static              -
  -------------------------------------------------------------------------     
  Total: 1 link aggregation(s)                                                  

Configuration File

link-aggregation 0/19 0-1 0/20 0-1 egress-ingress workmode lacp-static

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