The larger the environment, the more switches that make up the overall fabric and the greater the possibility for one component of the data center switching fabric to fail. A resilient fabric can sustain individual link or switch failures without widespread impact.

Compensation for a Link Failure
Even though spine switch S1 has failed, the leaf switches can connect to other spine switches and are not blocked.

For example, if one of the spine switches fails, traffic between racks continues to be routed across the remaining spine switches in a Layer 3 fabric. The routing protocol ensures that only available paths are chosen. Utilizing more than two spine switches reduces the impact of a spine switch failure. 

Multipathing-capable fabrics handle switch or link failures, reducing the need for manual network maintenance and operations. If a software upgrade of a fabric switch becomes necessary, the administrator can take the node out of service gracefully by changing routing protocol metrics, which will quickly drain network traffic from that switch, freeing the switch for maintenance.

Depending on the width of the spine, that is, how many switches are in the aggregation or spine layer, the additional load that the remaining switches must carry is not as significant as if there were only two switches in the aggregation layer. For example, in an environment with four spine switches, a failure of a single spine switch only reduces the available capacity by 25%.