Huawei Alibaba Huawei When a Spine-Leaf topology adopts the Intermediate System to Intermediate System (IS-IS) routing protocol, the Leaf node receives Link State Packets (LSPs) from all the other nodes thus having the entire routing information of the topology. This is usually considered unnecessary and costly. This document describes a solution to this problem by utilizing IS-IS's inherent multi-level and area partition features, which requires that an IS-IS router SHOULD check a level-1 LSP's area addresses before advertising it to a neighbor.