14. Bringing Up an Interface
• Conf t
• Interface ?
• No shutdown
• Ip address # #
15. Using the pipe |
• Pipe means: Output Modifier
• Show run | begin interface
• Show ip route | include #
16. Serial Interface Commands
• DCE vs. DTE ‘find the clock symbol’
• Add clocking to DCE only
– Does it really matter?
• Conf t
• Int serial ?
• Clock rate ?
• Show controllers
– Command that shows DCE connection
17. Viewing, Saving, and Erasing
Configurations
• Show running-config
• Show startup-config
• Copy running-config startup-config
• Erase start-up config
• Reload
– Take care
• Erase running-config
18. Verifying Settings
• Ping #destination-ip
• Ping
– Called: extended ping
• Traceroute #destination-ip
– No map this time
• telnet #destination-ip
• Show interface #interface-id
• Show ip interface
• Show ip interface brief
• Show protocols
• Show controllers #serial-id
19. Internal Components
• Bootstrap:
– Stored in ROM, used to bring router up during
initialization. Boot the router, load the IOS.
• POST:
– Stored in ROM, used to check the basic
functionality of the router hardware and
determines which interfaces are present
20. Internal Components
• RAM:
– Hold packet buffers, ARP cache, routing tables,
running-config, most routers expand IOS from flash to
RAM on boot
• ROM:
– Start and maintain the router. Hold Boot Strap, and
POST
• Flash Memory:
– Store CISCO IOS by default. It is not erased when
router is reloaded.
21. Internal Components
• NVRAM:
– Hold the router and switch configuration. Not
erased when device is reloaded. Does not store
IOS. Configuration Register is stored in NVRAM.
• Configuration Register
– Control how the router boots up. This value can
be found as the last line in #show version. Default:
0x2102 -> load IOS from flash and load
configuration from NVRAM
22. Router Boot Sequence
When router boots up, it performs sequence of
steps, called: Boot Sequence.
1. Router performs POST
2. Locate IOS. Bootstrap loads IOS.
24. Changing Configuration Register Value
• Main Reasons:
– Force system into the ROM monitor mode
– Select boot source
– Enable or disable Break function
– Control Broadcast addresses
– Set console terminal baud rate
– Load OS from ROM
– Enable booting from TFTP
26. • Router(config)#config-register 0x2101
• Show version
• Show flash
• Config-register 0x2102
• Reload
• Now What?
27. Recovering Passwords
• The default configuration register value is
0x2102, meaning that bit 6 is off. With the
default setting, the router will look for and
load a router configuration stored in NVRAM
(startup-config). To recover a password, you
need to turn on bit 6. Doing this will tell the
router to ignore the NVRAM contents. The
configuration register value to turn on bit 6 is
0x2142.
28. main steps to password recovery
1. Boot the router and interrupt the boot sequence by
performing a break, which will take the router into ROM
monitor mode.
2. Change the configuration register to turn on bit 6 (with the
value 0x2142).
3. Reload the router.
4. Enter privileged mode.
5. Copy the startup-config file to running-config.
6. Change the password.
7. Reset the configuration register to the default value.
8. Save the router configuration.
9. Reload the router (optional).
29. 1. Break the Boot Sequence
• Ctrl + Break
• While loading!
• Rommon: Rom Monitor Mode
