Why does a trunk interface not load balance packets with different MAC addresses


The load balancing function of the trunk interface takes effect only for known unicast packets.

To enable the load balancing function of the trunk interface for broadcast packets, Layer 3 multicast packets, and unknown unicast packets on the S3752 and the S5700, you can run the unknown-unicast load-balance command in the system view. At present, the S3728 and the S2700 do not support this command.

Other related questions:
Why cannot interfaces of different types generate equal-cost routes and establish OSPF load balancing
OSPF can automatically calculate the cost of an interface based on the interface bandwidth. The calculation formula is: Interface cost = Bandwidth reference value/Interface bandwidth. The bandwidth reference value is configurable. The default value is 100 Mbit/s. Routes generated by OSPF have the same priority (10 by default). The interface cost, however, depends on the interface type. Interfaces of different types have different costs; therefore, the interfaces cannot generate equal-cost routes, leading to failure in establishing load balancing.

Does the switch Eth-Trunk port support the enhanced load balancing mode
In the enhanced mode, the load balancing can be implemented based on the packet type. In V100R006 and earlier versions, the switches do not support this configuration. In V200R001, only the S5700HI and S5710EI support this configuration. In V200R200 and later versions, the S5700HI, S5710HI, and S5710EI support this configuration. The key configuration commands are as follows: 1. Run the load-balance-profile profile-name command to create the enhanced load balancing template and go to the template view. The load balancing mode can be configured for L2 packets, IPV4 packets, IPV6 packets, or MPLS packets. 2. Go to the Eth-Trunk port view, and run load-balance enhanced profile profile-name to use the enhanced load balancing mode for the Eth-Trunk.

How to configure load balancing for the Eth-Trunk on S series switches
S series switches (except the S1700) use a per-flow load balancing mechanism, which ensures that frames of the same data flow are forwarded on the same physical link, and different data flows are forwarded on different physical links. You can configure common load balancing mode to implement load balancing based on IP addresses or MAC addresses of packets. For L2, IP, and MPLS packets, you can also configure enhanced load balancing mode. Load balancing takes effect only for the outbound traffic. Therefore, load balancing modes can be different on the two ends of a link. 1. Commands for configuring common load balancing mode: [HUAWEI] interface Eth-Trunk 1 [HUAWEI-Eth-Trunk1] load-balance dst-mac 2. Commands for configuring enhanced load balancing mode: [HUAWEI] load-balance-profile a [HUAWEI-load-balance-profile-a] l2 field smac [HUAWEI-load-balance-profile-a] quit [HUAWEI] interface Eth-Trunk 1 [HUAWEI-Eth-Trunk1] load-balance enhanced profile a For configuration cases about common load balancing mode, see "Typical Ethernet Switching Configuration -Link Aggregation Configuration- Example for Configuring Link Aggregation in Manual Mode When Switches Are Directly Connected" in S1720&S2700&S3700&S5700&S6700&S7700&S9700 Typical Configuration Examples. The configuration cases of common load balancing are applicable to all S series switch models. The Sx700 series switch is used here as an example.

Load balancing principle of Eth-Trunk member interfaces on CE switches
An Eth-Trunk has 16 timeslots for sending packets at each interval. Eth-Trunk member interfaces use the 16 timeslots to send packets in sequence. When the number of Eth-Trunk member interfaces is the nth power of 2, load balancing can be made more even. For example, if the number of Eth-Trunk member interfaces is 2, 4, or 8 (which is divisible by 16), the timeslot of the packets sent by each interface is an integer, making load balancing even. If it is not the nth power of 2 (for example, 3), a member interface gets 6 times for sending packets from 16 timeslots, while the other two only get 5 times. In this way, load balancing is not even. Therefore, you are advised to set the number of Eth-Trunk member interfaces to the nth power of 2, ensuring even load balancing.

AP load balancing does not take effect
To implement load balancing, the following requirements must be met; otherwise, configurations fail or do not take effect. 1. The requirements for a radio to join a load balancing group are as follows: - A radio can join only one load balancing group. - The newly added radios must be of the same type as other radios in the load balancing group. Radios in a hotspot area must be of the same type. Otherwise, load balancing cannot be achieved. The type of radios in a load balancing group is determined by the type of the first added radio. - The channel of a new radio must be different from channels of other radios in the load balancing group. If the channel of a new radio is the same as channels of other radios in the load balancing group, a radio signal collision occurs. To improve coverage areas and minimize collisions, APs in a hotspot area must be configured with different channels. To detect channel collisions, check the configured channel and actual channel of the radio. - More radios can be added to a load balancing group if it is not full. In a load balancing group, radios must be configured with different channels and all these radios must be of the same type. In addition, radios of the same type support limited and fixed channels. Therefore, the number of radios in a load balancing group is limited. 2. The load balancing function applies to scenarios where there is a high degree of overlapping between APs' coverage ranges. You can adjust the AP power to enable the APs' coverage areas to overlap. When the load difference between APs reaches the load difference threshold, some STAs may access the network slowly, because the APs will reject access requests of STAs according to the load balancing algorithm. If a STA continues to send association requests to an AP, the AP allows the STA to associate when the number of consecutive association attempts of the STA exceeds the maximum number of rejection times.

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