How to change the ECMP load balancing mode on S series switches

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Equal-cost multi-path routing (ECMP) applies to the network where multiple links to the same destination are available. In the traditional routing technology, packets are forwarded to the destination through one link only; the other links are in backup or inactive state; switching between these links takes a certain period when dynamic routes are used. Different from the traditional routing technology, ECMP uses multiple links to increase transmission bandwidth and transmits data without any delay or packet loss in the case of a faulty link.
To configure the ECMP load balancing mode on ECMP-capable S series switches, run the ecmp load-balance sip [ dip ] [ port ] command in the system view. By default, packets are load balanced based on the source and destination IP addresses and the source port number at the transmission layer. When you repeatedly run the ecmp load-balance command in the system view, the latest configuration overrides the previous configuration.
Example:
Set ECMP load balancing based on the source IP address.
[HUAWEI] ecmp load-balance sip

Other related questions:
How to modify the ECMP load balancing mode of S series switch?
ECMP is applied to a network environment where multiple different links reach the same destination address.If you use traditional routing technology, packets destined for the destination address can only use one of the links, the other links in the backup state or invalid state, and in the dynamic routing environment to switch between each other takes some time. The ECMP can be used to multiple links in the network environment at the same time, not only increased the transmission bandwidth, and can be no delay without packet loss backup link data transmission.

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.

Which is the recommended load balancing mode on S series switches
Q: Which is the recommended load balancing mode on S series switches? A: If you know the rate of traffic from specified network segments, configure flow-based policy routing to forward traffic from specified network segments through specified outbound interfaces. If you have confirmed that the source and destination IP addresses of service flows are discrete, configure equal-cost routes to load balance the service flows.

How load balancing is implemented on S series switches when link aggregation is configured
For S series switches (except the S1700), there are two load balancing modes: per-packet load balancing and per-flow load balancing. 1. Per-packet load balancing mode When there are multiple physical links between the two devices of the Eth-Trunk, the first data frame of a data flow is transmitted on one physical link, and the second data frame is transmitted on another physical link. In this case, the second data frame may arrive at the peer device earlier than the first data frame. As a result, packet mis-sequencing occurs. 2. Per-flow load balancing mode This mechanism uses the hash algorithm to calculate the address in a data frame and generates a hash key value. Then the system searches for the outbound interface in the Eth-Trunk forwarding table based on the generated hash key value. Each MAC or IP address corresponds to a hash key value, so the system uses different outbound interfaces to forward data. This mechanism ensures that frames of the same data flow are forwarded on the same physical link and implements flow-based load balancing. Per-flow load balancing ensures the correct sequence of data transmission, but cannot ensure the bandwidth usage. Notes: Currently, S series switches support only per-flow load balancing mode, including the following: 1. Load balancing based on the source MAC address of packets; 2. Load balancing based on the destination MAC address of packets; 3. Load balancing based on the source IP address of packets; 4. Load balancing based on the destination IP address of packets; 5. Load balancing based on the source and destination MAC addresses of packets; 6. Load balancing based on the source and destination IP addresses of packets; 7. Enhanced load balancing for L2, IPv4, IPv6, and MPLS packets based on the VLAN ID and source physical interface number. When you configure load balancing modes, follow these guidelines: The load balancing mode only takes effect on the outbound interface of traffic. If load is unevenly distributed on the inbound interfaces, change the load balancing mode on the uplink outbound interfaces. Configure load balancing to ensure data flow is transmitted on all active links instead of only one link, preventing traffic congestion and ensuring normal service operation. For example, if data packets have only one destination MAC address and IP address, you are advised to configure load balancing based on the source MAC address and IP address. If you implement load balancing based on the destination MAC address and IP address, the data flow may be transmitted on only one link, causing traffic congestion.

Do S series switches support ratio-based load balancing
S series switches (except the S1700) support per-flow load balancing but do not support ratio-based load balancing.

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