, the configuration is a part of the Cisco IOS for the switch itself (assuming native IOS). Each of the modules is hot-swappable, with the only limitation being that some modules must be shut down before being removed. Also, because the modules communicate with each other over the backplane, they offer substantial increases in speed over their standalone counterparts. The FWSM, for example, capable of more than 4 Gbps of throughput, while the fastest standalone PIX fire- wall at the time of this writing is capable of only 1.8 Gbps. While this processing difference has a lot to do with the design of the FWSM and PIX firewalls, the fact remains that standalone devices must communicate through Gigabit Ethernet inter- faces, while service modules communicate directly over the backplane of the switch. 6500 switches are designed to be highly redundant. They support dual power sup- plies and dual supervisors. The supervisor MSFCs can run as individual routers or in single-router mode. The power supplies can be configured in a failover mode or a combined mode to allow more power for hungry modules. Combine this switch's features, scalability, and resilience with the additional fault- tolerance of a high-availability network design, and you've got a world-class architecture at your fingertips. Architecture The 6500-series switches are an evolution of the 6000 series. The 6000-series switch contained only a 32-Gbps backplane bus, whereas the 6500 series contains an addi- tional bus called the fabric bus or crossbar switching bus. This bus allows backplane speeds to be boosted up to 720 Gbps and beyond. The addition of the crossbar switching fabric in the 6500 series also provides an amazing amount of flexibility in the new chassis. Legacy modules from the 6000 chassis could still be used, as the 32 Gbps bus in the 6500 is identical to one found in the 6000 series. However, with the addition of a required Switch Fabric Module (SFM), newer fabric-enabled modules are able to take advantage of the new bus. The SFM is essential