CISCO NETWORKING ACADEMY Chabot College ELEC 99.08 Router Components & “Show” Commands.

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ELEC 99.08ELEC 99.08Router Components & “Show” Commands

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Internal ComponentsInternal Components

RAM NVRAM Flash ROM

InterfacesConsoleAuxiliary

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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

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NVRAMNVRAM

• Non-volatile RAM

• Stores backup/startup configuration files

• Content is not lost when router is powered down or restarted.

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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

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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

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InterfacesInterfaces

• Network connections through which packets enter and exit the router

• Attached to the motherboard or as separate modules on “modular” routers.

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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

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Programs include the bootstrap program that • tests the equipment (POST) • and locates the IOS.

RAM SpecificsRAM Specifics

RAMPrograms

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RAM SpecificsRAM Specifics

RAMInternetwork

OperatingSystem(IOS)

Programs

Once the IOS is located by the bootstrap program, it is loaded in to RAM.

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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.

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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.

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RAM SpecificsRAM Specifics

RAMCommandExecutive

InternetworkOperating

System(IOS)

ProgramsActiveConfig

FileTables

The tables are loaded from the configuration file including...• ARP Tables• Routing Tables

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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.

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Router Status CommandsRouter Status Commands

• “Show” commands yield status information about various router components, as shown on the next slides...

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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)

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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

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Example Show CommandsExample Show Commandsshow running-config

– displays the active configuration file loaded in RAM

Try it now with Router e-SIM

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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

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Example Show CommandsExample Show Commandsshow interfaces

– displays statistics for all interfaces configured on the router

Try it now with Router e-SIM.

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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.

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Example Show CommandsExample Show Commandsshow ip route

– displays the routes to all networks known to the router

Try it now with Router e-SIM.

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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...

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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