How to configure link redundancy on S series switches


S series switches (except the S1700) support link redundancy by using stacking, link aggregation, or VRRP.

Other related questions:
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.

Does an S series switch support link aggregation after stacking configuration
S series switches (except the S1700) support link aggregation after stacking configuration.

Why configure OSPF virtual links on S series switches
Question: What are the functions of OSPF virtual links configured on S series switch supporting OSPF? Answer: OSPF virtual links can connect areas that are not physically connected to the backbone area to the backbone area so that these areas can route traffic normally. This function is mainly used to merge networks. Virtual links also improve network reliability by allowing normal routing after the physical connection to the backbone area is down. On actual networks, virtual links are seldom used. Generally, networks are planned properly and areas are seldom physically disconnected from the backbone areas. It is rare that networks are merged without network re-planning. In addition, virtual links are seldom used to enhance the robustness of backbone areas.

Why configure sham links for OSPF on S series switches
In Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) configuration, OSPF is used as the routing protocol between PEs and CEs so that the sites in a VPN can be connected through the MPLS backbone network. Though the connectivity between OSPF PEs and CEs ensures the connectivity between VPN sites, the intra-area link between VPN sites should also be considered. For two sites that belong to the same site, the path through the intra-area link is always preferred because, according to OSPF specifications, an intra-area path is always preferred to an inter-area path. Therefore, when an intra-area link exists, you can control routes through a policy. If the intra-area link is used for backup only, the default processing flow will be unacceptable. For connections to be re-established between sites through the MPLS VPN backbone area, a logical intra-area link must be established between the ingress and egress Virtual Routing and Forwarding (VRF) interfaces of the related PEs. An OSPF sham link can be established between two sites as an intra-area channel to enable the two sites to communicate with each other through the MPLS backbone area, and the intra-area link is used for backup. If no intra-area link exists between the two sites, no sham link is required.

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