An input/output (I/O) switch fabric includes input physical ports that convey packets associated with at least a first network flow. Moreover, virtual routers in the I/O switch fabric, which have associated routing tables, provide types of service and/or routes for different source-destination pairs based on link-layer information and network-layer information in the packets. Note that different virtual routers can provide different types of service and/or different routes. For example, a type of service associated with a first virtual router may include changing packet headers when crossing service domains in a global network, and a type of service associated with a second virtual router may avoid changing packet headers when providing connectivity in the network. Furthermore, the I/O switch fabric includes output physical ports that convey packets associated with at least a second network flow. The virtual routers may facilitate InfiniBand inter-subnet crossing.