Some routers do not
load the Cisco IOS Software image into RAM, but execute it directly
from ?¬‚ash memory.
Step 5 The default is to look in NVRAM for a valid saved con?¬?guration ?¬?le,
called startup-con?¬?g.
Step 6 The desired con?¬?guration for the router is loaded and executed. If no
con?¬?guration exists, the router will enter the setup utility or attempt an
AutoInstall to look for a con?¬?guration ?¬?le from a TFTP server.
Internal Router Components
The major internal components of a Cisco router include the interfaces, RAM, ROM, ?¬‚ash
memory, NVRAM, and the con?¬?guration register.
The major components of a router are shown in Figure 6-5.
Managing Cisco Router Startup and Configuration 435
Figure 6-5 Router Components
Most of these components are hardware, as follows:
?– CPU: This is the processor that runs the Cisco IOS and features like route processing.
?– RAM: This read/write memory contains the software and data structures that enable
the router to function. The principal software running in RAM is the Cisco IOS
Software image and the running con?¬?guration. The RAM also contains the routing
tables and packet buffers. RAM is volatile; its memory contents will be lost when
power is turned off.
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