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The IOS and Its User Interface
27
·
ROM
--This type of memory (read-only memory) stores a bootable IOS image, which is
not typically used for normal operation. ROM contains the code that is used to boot the
router until the router knows where to get the full IOS image.
·
Flash memory
--Either an EEPROM or a PCMCIA card, Flash memory stores fully
functional IOS images and is the default where the router gets its IOS at boot time. Flash
memory also can be used to store configuration files on Cisco 7500 series platforms.
·
NVRAM
--Nonvolatile RAM stores the initial or
startup
configuration file.
All these types of memory are permanent memory except RAM. No hard disk or diskette
storage exists on Cisco routers. Figure 2-2 summarizes the use of memory in Cisco routers.
Figure 2-2
Cisco Router Memory Types
The processors in the routers vary from model to model. Although they are not specifically
listed as requirements for the CCNA exam, some reference to terminology is useful. In most
routers, only one processor option is available; thus, you would not order a specific processor
type or card. The exception to this is the 7200 and 7500 families of routers. For instance, on the
7500 series, you choose either a Route Switch Processor 1 (RSP-1), RSP-2, or RSP-4
processor. In any case, all 7200 and 7500 routers, as well as most of the other Cisco router
families, run IOS. This commonality enables Cisco to formulate exams, such as CCNA, that
cover the IOS features without having to cover many hardware details.
Interfaces are used by a router for routing packets and bridging frames through a router. The
types of interfaces available change over time due to new technology. For example, packet-
over-SONET and voice interfaces are relatively recent additions to the product line. However,
some confusion exists about what to call the actual cards that house the physical interfaces.
Table 2-2 summarizes the terminology that might be referred to on the test.
Table 2-2
Samples of Router Interface Terminology
Model Series
What the IOS Calls
Interfaces
What the Product Catalog Calls the Cards
with the Interfaces on Them
2500
Interface
Modules and WAN interface cards
3600
Interface
Network modules and WAN interface cards
4500
Interface
Network processor modules
7200
Interface
Port adapters and service adapters
7500
Interface
Interface processors, and versatile interface
processors with port adapters
RAM
(Working
Memory)
Flash
(IOS)
ROM
(IOS)
NVRAM
(Config)
ch02.fm Page 27 Monday, March 20, 2000 4:57 PM