A hybrid server and multi-layer switch system architecture, referred to hereinafter as the Enterprise Fabric (EF) architecture, forms the basis for a number of Enterprise Server (ES) chassis embodiments. Each ES embodiment generally includes one or more Processor Memory Modules (PMMs, each generally having one or more symmetric multiprocessor complexes), one or more Network Modules, and a System Control Module (SCM). The SCM includes a cellified switching-fabric core (SF) and a System Intelligence Module (SIM). Each PMM has one or more resident Virtual IO Controller (VIOC) adapters. Each VIOC is a specialized I/O controller that includes embedded layer-2 forwarding and filtering functions and tightly couples the PMM to the SF. Thus the layer-2 switch functionality within the ES chassis is distributed over all of the SCM, NM, and PMM modules. Through the use of VIOC/VNIC device drivers, host operating system software (Host O/S) running on the PMMs is presented with a plurality of Virtual Network Interface Cards (VNICs). In some embodiments, each VNIC behaves as a high-performance Ethernet interface at the full disposal of the Host O/S. In other embodiments, at least some of the VNICs behave as high-performance Fiber Channel Host Bus Adapters.