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CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Chabot CollegeChabot College
ELEC 99.08ELEC 99.08Router Components & “Show” Commands
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Internal ComponentsInternal Components
RAM NVRAM Flash ROM
InterfacesConsoleAuxiliary
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAMRAM
• Temporary storage for router configuration files
• RAM content is lost on power down or restart
• Stores...– Routing tables– ARP cache– Fast switching cache– Packet buffering
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
NVRAMNVRAM
• Non-volatile RAM
• Stores backup/startup configuration files
• Content is not lost when router is powered down or restarted.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
FlashFlash
• EEPROM (Electronically Erasable Programmable Read-Only Memory)
• Holds the Cisco IOS (Internetworking Operating System)
• Allows updating of software without replacing the Flash chip
• Multiple versions of IOS can be stored• Retained on power down
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
ROMROM
• Contains POST (Power On Self Test)
• A bootstrap program (loads the Cisco IOS)
• And mini-operating system software:– Backup, trimmed down version of the IOS– Upgrades require installing new chip set
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
InterfacesInterfaces
• Network connections through which packets enter and exit the router
• Attached to the motherboard or as separate modules on “modular” routers.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM NVRAM Flash ROM
InterfacesConsoleAuxiliary
As the router is booted, the following is loaded into RAM’s Working Storage.
RAM SpecificsRAM Specifics
RAMCommandExecutive
InternetworkOperating
System(IOS)
ProgramsActiveConfig
FileTables Buffers
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Programs include the bootstrap program that • tests the equipment (POST) • and locates the IOS.
RAM SpecificsRAM Specifics
RAMPrograms
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM SpecificsRAM Specifics
RAMInternetwork
OperatingSystem(IOS)
Programs
Once the IOS is located by the bootstrap program, it is loaded in to RAM.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM SpecificsRAM Specifics
RAMCommandExecutive
InternetworkOperating
System(IOS)
Programs
Part of the IOS is the Command EXEC. This is the program that translates the commands you type into a language that the IOS can understand.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM SpecificsRAM Specifics
RAMCommandExecutive
InternetworkOperating
System(IOS)
ProgramsActiveConfig
File
Once the IOS is initialized, it looks for an active configurations file (usually in NVRAM) and loads it. This file tells the router specifically what to do.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM SpecificsRAM Specifics
RAMCommandExecutive
InternetworkOperating
System(IOS)
ProgramsActiveConfig
FileTables
The tables are loaded from the configuration file including...• ARP Tables• Routing Tables
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
RAM SpecificsRAM Specifics
RAMCommandExecutive
InternetworkOperating
System(IOS)
ProgramsActiveConfig
FileTables Buffers
Finally, all leftover memory in RAM is used as the buffer for processing incoming and outgoing packets.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Router Status CommandsRouter Status Commands
• “Show” commands yield status information about various router components, as shown on the next slides...
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow version
– displays:
• configuration of the system hardware
• IOS version
• names and sources of configuration files
• the current setting of the configuration register(used in password recovery)
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow version
Try it now with Router e-SIM:
– Start Router e-SIM
– Give all your routers a configuration:
• click SHOW DONE
• in the row of SET buttons at the bottom, click A, B, C, D, E
• click HIDE DONE
– Login - Password - cisco
– Enable privileged mode: Secret Password: class
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow running-config
– displays the active configuration file loaded in RAM
Try it now with Router e-SIM
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow startup-config
– displays the backup configuration file stored in NVRAM
Try it now with Router e-SIM:
• Your router will not have a startup configuration until you save the running configuration to the startup file:
Lab_A# copy run start
• Now try show start again
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow interfaces
– displays statistics for all interfaces configured on the router
Try it now with Router e-SIM.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow protocols
– displays the status of all configured Layer 3 protocols
– displays the status of all interfaces
Try it now with Router e-SIM.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow ip route
– displays the routes to all networks known to the router
Try it now with Router e-SIM.
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
Example Show CommandsExample Show Commandsshow controller
– displays information about each interface controller.
Key: shows whether serial interface is DTE or DCE (setting determined by the connected cable).
Important mainly in Cisco lab, where some routers are configured DCE.
Router e-SIM doesn’t understand this command, so you’ll need to try it on a real router...
CISCO NETWORKING ACADEMYCISCO NETWORKING ACADEMY
FlashNVRAMRAM
Internetwork Operating System
ProgramsActive
ConfigurationFile
Tablesand
Buffers
BackupConfiguration
File
OperatingSystems
Inte
rface
sRouter#show version Router#show flash
Router#show interfaces
Router#show processes CPURouter#show protocols
Router#show running-config
Router#show ip routeRouter#show buffers
Router#show startup-config