Cisco Switching Products at different layers

Cisco Systems Inc. supports a broad range of local area network (LAN) switching architecture technologies and platforms.  The general minimal requirements that the Cisco switching platforms are designed to address include the following:

• High-performance switched Ethernet, capable of delivering 100 Mbps and 1Gbps to the desktop, and 1Gbps or 10Gbps uplinks.
• Quality of Service (QoS) features permitting prioritization of delay-sensitive traffic and control over packet delay and jitter.
• Simple, highly structured, and deterministic design (Predictable – in both normal and failure recovery modes).
• Support for both IP version 4 and IP version 6 protocols.
• Fault tolerance (Redundancy for critical components and links ‑ eliminating network single-points-of-failure).
• Flexibility (Network logically partitioned at Layers 2, 3 and 4, to direct traffic flow).
• Secured through authentication, authorization and accounting (AAA) controls.
• Modular design capable of supporting new applications and network growth without requiring “fork-lift” upgrades.
• Scalability for cost-effective delivery of the smallest to the largest telecommunications rooms and campuses
• Multicast protocol support for end-to-end management and optimization of streaming content delivery.
• Switches capable of powering IP telephones (via phantom power).
• Capable of being remotely monitored and managed using network management tools, such as HP Openview.

All Cisco switches are based on a distributed hardware architecture in which the LAN switching functions are separated from the “control plane” functions of switch management by utilizing both one or more general-purpose central processing chips and port or line card application-specific integrated circuits (ASICs).
The general-purpose CPU handles network management functions, like user logins, SNMP, and maintenance operations like operating system booting.  The general-purpose processor controls the configuration of the switch platforms with a command-line interface.  The ASICs optimize packet and frame switching at the port and line card level in order to reduce inter-frame delays and increase overall system throughput.
Older Cisco switches used an operating system called CatOS, with a command-line syntax based on set and clear statements.  Newer switch use an operating system referred to as the Cisco Internetwork Operating System (IOS), which is common across both switching and routing platforms.  The older CatOS is end-of-life and end-of-sale.  Only configurations involving IOS will be shown here.  A newer switching operating system based on the Cisco next-generation Nexus platforms is called NXOS, but is nearly identical to the IOS command syntax, and most of the Cisco switch product is based on IOS.
Cisco switching utilizes recommendations for a hierarchical design in switched network infrastructures, called core, distribution, and access layers.  It is acceptable to combine the functions of the core and distribution layers in smaller switched networks, which is called a collapsed core design.  The functions of each layer are as follows:
Core layer

• Links to WAN (Internet or other wide-area network)
• Links to distribution switches
• Additional Virtual Local Area Networks (VLANs) —Used by the system for routed ports as well as WAN ports

Distribution Layer

• Server connections
• Links to downstream (closet) access switches via layer 2 or layer 3 links.
• Site services, like wireless LAN controllers
• Service VLANs—To forward traffic to the service modules, such as the client VLAN of a content switch
• Fault tolerant VLANs—For redundancy with CSM, FWSM, CSS, and so forth

Access Layer

• Client connectivity at 10/100/1000Mbps