Networking - Understanding Chassis devices

A chassis in networking is a metal frame that can host a series of different types of modules. Chassis devices are typically switches, but they can also be routers or firewalls as well.

This modular design allows for scalability and flexibility, enabling the addition or removal of modules as needed. For example, the Cisco 9400 switch is a chassis switch with slots for different blades, each providing various interfaces and capabilities.

When purchasing a chassis switch or router, you typically buy the chassis and the necessary cards for your current needs. The modular nature allows for future expansion or modification over the device's lifetime.

A line card is a module inserted into these devices, providing interfaces for the device. For instance, a Cisco 9400 switch can have line cards with different types of ports, such as SFP ports for fiber connections or RJ-45 Ethernet ports.

An empty chassis consists of a backplane and a fan tray, with no intelligence. To add intelligence, you need an RSP (Route Switch Processor) or supervisor engine, which includes CPU, memory, and other necessary circuitry. Multiple supervisor engine models are available, offering varying capabilities. Redundancy can be achieved by using two supervisor engine cards.

You must think about a chassis switch in the same way as a non-modular switch, except that the various components of the switch are separated onto different components (line cards and supervisor engines) for the purpose of modularity.