Router Overview - Router Ports and Modules
(Page 11 of 15 )
A router’s window to the internetwork is through its ports and modules. Without them, a router is a useless box. The ports and modules that are put into a router define what it can do.
Internetworking can be intimidating, with the seemingly endless combinations of products, protocols, media, feature sets, standards—you name it. The acronyms come so fast and so hard that it might seem hopeless to learn how to properly configure a router. But choosing the right router product can be boiled down to manageable proportions. Table 4-4 lays out five major requirement areas that, if met, will lead you to the best router solution.
Cisco obviously can’t manufacture a model of router to match every customer’s specific requirements. To make them more flexible to configure, routers come in two major parts:
- ▼ Chassis The actual box and basic components inside it, such as power supply, fans, rear and front faceplates, indicator lights, and slots
- ▲ Ports and modules The printed circuit boards that slide into the router box
Cisco’s router product-line structure tries to steer you to a product—or at least to a reasonably focused selection of products—meeting all five requirement areas in Table 4-4.
Finding the right router for your needs is basically a three-step process. The following illustrates the process of selecting a router for a large branch office operation:
First, Cisco’s routers are grouped into product families called series. Choosing a router product series is usually a matter of budget, because each series reflects a price/ performance tier. Models within series are generally based on the same chassis, which is the metal frame and basic components (power supply, fans, and so on) around which the router is built. We’ll select the Cisco 2000 Series because it fits both the purchase budget and performance requirements for our large branch office.
From the 2000 Series, we’ll take the Cisco 2600 Series. The 2600 chassis is versatile enough to fit a lot of situations, making it a popular brand of branch office router.
Third, we’ll select the Cisco 2650 because it has two Ethernet ports; and our imaginary branch office will operate two subnets, one for the customer service office and another for the front office. The two Ethernet ports will let us separate the two departments, thereby isolating traffic.
NOTE: The term “port” can cause confusion if you’re not careful. When speaking of hardware, port means a physical connection through which I/O can pass(a serial port, for example), but there are also so-called ports at the transport layer of network protocols. These “ports” are actually port numbers used to identify what network application packets contain. These ports (port numbers) are also referred to as TCP ports or “listeners,” because they inform the receiver what’s inside the message. Example TCP-defined port numbers include Port 25 for Simple Mail Transfer Protocol and Port 80 for HTTP. Refer to Chapter 2’s section, “The Transport Layer,” for more on TCP ports.
 This chapter is from Cisco: A Beginner's Guide, by Velte and Velte (McGraw-Hill/Osborne, 2004, ISBN: 0072256354). Check it out at your favorite bookstore today.
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