A minimum of 128MB DRAM is generally required for stable operation of the IP Services feature set on IOS 15.
The "IP Services" feature set transforms the Catalyst 3560 from a basic multilayer switch into a robust edge router. c3560ipservicesk9mz1502se11bin upd
Comprehensive support for IP unicast and multicast routing, Policy-Based Routing (PBR), and fallback bridging. A minimum of 128MB DRAM is generally required