Hardware, Ports, and Lights– Cisco Basic Network Hardware
Racks of equipment, wire running all over the place, lights blinking on and off—when you walk into a large room holding lots of networking gear, you might wonder, “What is all this stuff?” You might feel like the person in Figure 10-1.
Figure 10-1 Racks of Equipment
The good news is there are only a few classes of equipment in any data processing or networking facility:
• Routers
• Patch panels
• Compute servers
• Storage devices
• Optical gear
• Other middleboxes
The bad news is all these kinds of devices tend to look alike.
Figure 10-2 shows a few pieces of computer networking equipment of different kinds (without wiring).
Figure 10-2 Stacked Networking Equipment
From top to bottom, Figure 10-2 shows:
• A Cisco 4000 series integrated services router (ISR). You would generally see this kind of router in a small office, where it provides connectivity to the corporate network and Internet as well as voice, security, and other services.
• A Cisco 1004 series optical networking convergence system.
You would generally see this type of device in a service provider facility or perhaps used for corporate campus connectivity.
• A Cisco UCS C220 rack server. This is a set of hosts attached to the network rather than providing network connectivity.
• A Cisco email security appliance. This specialized appliance is wired into the network so email traffic can pass through rather than providing network connectivity.
In Figure 10-2, each device’s height is labeled in rack units (RUs). An RU is 1.75 inches or 44.45 mm high. Designers are always trying to make more functionality fit into a single RU.
Equipment with more ports, or requiring more cooling surface, will require more RUs.
Beyond making broad generalizations, the only way to know which equipment does what is to read the labels and recognize broad classes of equipment based on their model numbers.
Recognizing hardware based on model numbers is not as hard as it might seem because most companies use only a limited range of equipment. For example, they will use only a few models of routers, switches, and other appliances in any individual facility.
Because the ISR router serves many different purposes, it has many kinds of ports. Look at each section of the ISR’s back
panel, beginning with the upper-left corner in Figure 10-3.
Figure 10-3 ISR Upper-Left Corner Ports
The first ports on the left, up to the two 10 Gb/s ports, are fixed.
You cannot replace fixed ports. Note the lack of screws or a separate plate, unlike the four ports on the left.
The management network port connects to a low-speed (normally 1 Gb/s) network to access and manage network equipment. User data is never carried over this network, usually called the out-of-band management network. Not all operators build out-of-band management networks. Instead, they manage all their equipment in-band, using the same network to carry management and user traffic.
The auxiliary port and console port provide access to the router’s command-line interface (CLI) via a terminal application.
Console connections come in many forms, including lower-speed Ethernet ports, various kinds of universal serial bus (USB), and multi-pin serial connectors. Most network engineers who spend a lot of time working with physical hardware build a collection of connectors to connect a laptop or tablet computer to network equipment.
Operators typically use console ports to configure a device to connect to the network. Once the device is connected, operators use telnet, Secure Shell (SSH), and other methods to connect to and configure the device. You can think of the console port in most modern networks as a sort of “backup plan”; this is how you connect if all the other ways fail.