China Mobile eBay Nvidia Google IS-IS is a commonly used routing protocol in MSDC (Massively Scalable Data Center) networks where CLOS is the most popular topology. In a CLOS topology, each IS-IS router would receive multiple copies of the same LSP (Link State Packet) from multiple IS-IS neighbors. Moreover, two IS-IS neighbors may send each other the same LSP simultaneously. The unnecessary link-state information flooding results in a large waste of resources for IS-IS routers, as there are too many neighbors for each router. To address this scaling problem, this document introduces some extensions to the IS-IS protocol. These extensions aim to significantly reduce the IS-IS flooding within MSDC networks, which can greatly improve the scalability of such networks.