13-07-2012, 04:46 PM
Cisco Router Configuration Basics
[attachment=27592]
Router Components
Bootstrap – stored in ROM microcode – brings router up during initialisation, boots router and loads the IOS.
POST – Power On Self Test - stored in ROM microcode – checks for basic functionality of router hardware and determines which interfaces are present
ROM Monitor – stored in ROM microcode – used for manufacturing, testing and troubleshooting
Mini-IOS – a.k.a RXBOOT/boot loader by Cisco – small IOS ROM used to bring up an interface and load a Cisco IOS into flash memory from a TFTP server; can also perform a few other maintenance operations
Purpose of the Config Register
Reasons why you would want to modify the config-register:
Force the router into ROM Monitor Mode
Select a boot source and default boot filename
Enable/Disable the Break function
Control broadcast addresses
Set console terminal baud rate
Load operating software from ROM
Enable booting from a TFTP server
Where is the Configuration?
Router always has two configurations:
Running configuration
In RAM, determines how the router is currently operating
Is modified using the configure command
To see it: show running-config
Startup confguration
In NVRAM, determines how the router will operate after next reload
Is modified using the copy command
To see it: show startup-config
Router Access Modes
User EXEC mode – limited examination of router
Router>
Privileged EXEC mode – detailed examination of router, debugging, testing, file manipulation (router prompt changes to an octothorp)
Router#
ROM Monitor – useful for password recovery & new IOS upload session
Setup Mode – available when router has no startup-config file
Using Access Control Lists (ACLs)
Access Control Lists used to implement security in routers
powerful tool for network control
filter packets flow in or out of router interfaces
restrict network use by certain users or devices
deny or permit traffic
[attachment=27592]
Router Components
Bootstrap – stored in ROM microcode – brings router up during initialisation, boots router and loads the IOS.
POST – Power On Self Test - stored in ROM microcode – checks for basic functionality of router hardware and determines which interfaces are present
ROM Monitor – stored in ROM microcode – used for manufacturing, testing and troubleshooting
Mini-IOS – a.k.a RXBOOT/boot loader by Cisco – small IOS ROM used to bring up an interface and load a Cisco IOS into flash memory from a TFTP server; can also perform a few other maintenance operations
Purpose of the Config Register
Reasons why you would want to modify the config-register:
Force the router into ROM Monitor Mode
Select a boot source and default boot filename
Enable/Disable the Break function
Control broadcast addresses
Set console terminal baud rate
Load operating software from ROM
Enable booting from a TFTP server
Where is the Configuration?
Router always has two configurations:
Running configuration
In RAM, determines how the router is currently operating
Is modified using the configure command
To see it: show running-config
Startup confguration
In NVRAM, determines how the router will operate after next reload
Is modified using the copy command
To see it: show startup-config
Router Access Modes
User EXEC mode – limited examination of router
Router>
Privileged EXEC mode – detailed examination of router, debugging, testing, file manipulation (router prompt changes to an octothorp)
Router#
ROM Monitor – useful for password recovery & new IOS upload session
Setup Mode – available when router has no startup-config file
Using Access Control Lists (ACLs)
Access Control Lists used to implement security in routers
powerful tool for network control
filter packets flow in or out of router interfaces
restrict network use by certain users or devices
deny or permit traffic