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According to Huawei data center network design guidelines, the selection of an underlay routing protocol depends on the scale and complexity of the network. For small to medium-sized data centers , particularly when the number of ToR (Top of Rack) switches is less than 100 , OSPF (Open Shortest Path First) is the recommended routing protocol.

OSPF is a mature and widely deployed link-state protocol that offers fast convergence, simple configuration, and strong interoperability. It is well-suited for smaller-scale spine-leaf networks where operational simplicity is a priority. Huawei recommends OSPF in such scenarios because it provides sufficient scalability and performance without the added complexity of protocols like BGP.

For larger-scale data centers (typically more than 100 ToR switches), Huawei suggests using IS-IS or BGP to improve scalability and simplify large-scale route management. RIP is not suitable due to its limitations in scalability and convergence speed.

Therefore, for networks with fewer than 100 ToR switches, OSPF is the optimal and recommended choice .