| Existing and emerging layer-4 switching technologies require packet classication to be performed on more than one header elds, known as layer-4 lookup. Currently, the fastest general layer-4 lookup scheme delivers a throughput of 1 Million Lookups Per Second (MLPS), far o from 25/75 MLPS needed to support 50/150 Gbps layer4 router. We propose the use of route caching to speed up layer-4 lookup, and design and implement a cache architecture for this purpose. We investigated the locality behavior of the Interent trac (at layer-4) and proposed a near-LRU algorithm that best harness this behavior. In implementation, to best approximate fully-associative nearLRU using relatively inexpensive set-associative hardware, we invented a dynamic set-associative scheme that exploits the nice properties of N-universal hash functions. The cache architecture achieves a high and stable hit ratio above 90 percent and a fast throughput up to 75 MLPS at a reasonable cost ($700/1700 for 50/150 Gbps rou...