Transcript Network Devices - Pennsylvania State University

IST 228\Ch7: Managing Cisco...
Router Components: ROM
• Read-only memory (ROM)
• Stores:
– the bootstrap program, also called the ROM Monitor,
that initializes the router’s basic hardware
components.
– POST (power-on self test), that checks the basic
functionality of the router hardware and determines
interfaces.
– Mini-IOS, which is used to bring up an interface.
• ROM monitor mode
– Router mode that allows to configure your router in
the event that there is no valid IOS file on your flash
memory
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IST 228\Ch7: Managing Cisco...
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Router Components: RAM
RAM stores following components:
(3) Command
Executive
(2) Internetwork Operating System
(IOS)
RAM
Commands are loaded.
(1)Programs
POST and
bootstrap to test
the equipment
and locate the
IOS
The IOS is located by the bootstrap program, it
is loaded in to RAM
(4) Running
Config. File
the IOS loads active
configuration file
(usually from
NVRAM)
(5) Tables
ARP and
routing tables
(6) Buffers
used for routing
incoming and
outgoing
packets
IST 228\Ch7: Managing Cisco...
Router Components: NVRAM
• Nonvolatile random access memory
(NVRAM)
– Special type of RAM
– Not cleared when the router is rebooted
– Startup configuration for the router is stored in
NVRAM by default
– Stores all the user-defined configuration
information for the router
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IST 228\Ch7: Managing Cisco...
Router Components: Flash Memory
• Erasable, programmable, read-only
memory (EPROM)
– Not typically modified during normal
operations
– Can be upgraded or erased when necessary
– Content of flash memory is maintained even
when the router is rebooted
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Show Commands
R#show flash
R#show version
RAM
R#show interfaces
NVRAM
Flash
Backup
Configuration
File
Operating
Systems
Internetwork Operating System
Programs
Running
Configuration
Table
and
Buffers
R#show mem
R#show stacks
R#show buffers
R#show running-config
R#write term
R#show process CPU
R#show protocols
Interfaces
R#show startup-config
IST 228\Ch7: Managing Cisco...
Startup
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IST 228\Ch7: Managing Cisco...
Managing Configuration Registers
• 16-bit software register, which is written
into NVRAM.
• By default, it is set to load IOS from flash
memory and look for startup-configuration
from NVRAM.
• ..\Calc\config_register.exe
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IST 228\Ch7: Managing Cisco...
Checking Current Configuration
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IST 228\Ch7: Managing Cisco...
Chancing the Configuration Register
Router(config)#config-register 0x101.
Recovering Passwords: pp. 356-359
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