Role of Switched Networks

A few years ago the flat Layer 2 switched networks were the standard. Flat Layer 2 data networks work on the basic principles of Ethernet and the common use of hub and repeaters to broadcast LAN traffic throughout a campus. As shown in Figure 1, networks have primarily changed to switched LANs in a hierarchical network. A switched LAN allows traffic management, additional flexibility, and extra features, such as:

• QoS


• Wireless network connectivity and support


• IP telephony and mobility services


• Additional security

Form Factors

Different types of switches are used in a business network. Considering common business requirement the appropriate switched equipment selection is a very important factor.  Selecting the type of switch the network administrator and designer must select a modular or fixed configuration and stackable or non-stackable. The physical installation is also an important consideration of the switch. The thickness of the switch decides where to install the switch. The switch can be installed in a rack or in a cabinet. These options are sometimes referred to as switch form factors, which I am going to explain below:-

Fixed Configuration Switches

Fixed Configuration switches are switches with a fixed number of ports and are normally not expandable. These switches do not support features or options further than those that originally came with the switch. The switch model determines the features and options available. Such as, if you have a 16-port gigabit fixed switch, you cannot add additional ports when you need them. This category is discussed in further detail below. Cisco Catalyst 2K, 3K, and the Cisco 300/500 series are good examples of Fixed Configuration switches. The Fixed configuration switch category is further broken down into:

• Unmanaged Switches


• Smart Switches


• Managed L2 and L3 Switches

Modular Configuration Switches

Modular switches are expendable switches comes with different sized chassis which allow a different number of modular line cards inside the chassis. The modular switches offer more flexibility in their configuration. If you have a 24 port modular switch you can easily expand the switch to 48 port.  

Stackable Configuration Switches

A stackable switch is a switch that is completely functional operating standalone but which can also be set up to operate jointly with one or more other switches in a group. This group of switches will show the characteristics of a single switch but have the port capacity of the sum of all switches. Stackable switches can be interconnected using a special cable that provides high-bandwidth throughput between the switches. The Cisco Stack Wise Technology allows the interconnection of nine switches in the group. These stacked switches effectively operate as a single larger switch.

Cisco Borderless Network

With the rising demands of the converged network, the recent developments in network design are the Cisco Borderless Network. The Cisco Borderless Network is a network design that allows organizations to support a borderless network that can connect any person, everywhere on any device very securely and consistently. This design address IT and business challenges.

The Cisco Borderless Network structure merge wired and wireless access, as well as access control, policy; and performance management of different device types. Using the Cisco Borderless Network architecture is built on a hierarchical infrastructure of hardware that is scalable and flexible, the Figure below illustrates the Cisco Borderless Network which provides two primary sets of services: network services and endpoint services; all services managed by an integrated management solution. This design enables different network elements to work mutually and also allow to access resources from any place at any time; as providing optimization, scalability as well as security.

Hierarchy in the Cisco Borderless Network

Availability, flexibility, security, and manageability is the primary requirement of the borderless switched network. The borderless switched network should deliver current and future requirement. The basic principles of the Borderless switched network are the following:

• hierarchical network Design


• Modularity


• Resiliency


• Flexibility

Understanding the principle to fits in the different situation is very important. The hierarchical borderless 

switched network is providing a base for the network designer to cover security, mobility, and unified communication features. Cisco designs three-tier and two-tier hierarchical network for a campus. The figure below illustrates the Cisco hierarchical network design. The three-tier of this design are the access, distribution, and core layers.  Every layer of this design can be seen as a clear structured module with particular roles and functions in the campus network.

The campus hierarchical network design which containing modularity provide critical network services with resilient and flexible.  The modularity also provide assistance for increase and change that occurs over time

Access, Distribution, and Core Layers

Access Layer

The access layer is the place where traffic enters or exits the campus network. It is the edge of the campus network. Usually, the main function of an access layer is to provide network connectivity and access to end users.  The switches of the access layer connect to switches of the distribution layer. The switches in the distribution layer apply network foundation technologies such as routing, QoS, and security.

To meet user requirement and network application, the next-generation switching platforms currently present extra converged integrated; and quick services to different types of endpoints at the edge of the network. Creating intelligence into the switches of an access layer allows applications to function on the network more capable and securely.

 Distribution Layer

The distribution layer provides connectivity between access layer and core layer with many important functions. This layer provides intelligent switching and routing. The distribution layer provides network access policy functions to access the whole network as long as differentiated services to different classes of service applications at the edge of the network. This layer providing high ease of use throughout redundant distribution layer switches to the end-user and equal cost paths to the core layer. The distribution layer also aggregate large-scale wiring closet networks and aggregate Layer 2 broadcast domains and Layer 3 routing boundaries

Core Layer

This layer is the backbone of the Cisco borderless network. The core layer connects a number of layers of the campus network and work as the aggregator for all of the other campus blocks and interconnects the campus with each other inside the network. The core layer main function is to provide speedy fault isolation and high-speed backbone connectivity.

Collapsed Core Network

Three-tier campus network usually planed for organizations where the access, distribution, and core, each are required as separate layers. This is required because of a basic, cost-effective, scalable, and efficient physical layout design for the large-scale network where many campuses exist. The best practice is to make an extended-star 

physical topology from the main campus to all other campuses.

The campus where fewer users accessing the network or single building campus usually not required a separate core and distribution layers. Network structure required in this situation is called a collapsed network or two-tier campus network.  In a collapsed network the role of the core switches moves to the distribution switches, merging the core- and distribution layer.

The figure below illustrates the collapsed campus network example for where the distribution and core layers are collapsed into a single layer.