1. Chapter 5: Managing a Cisco Internetwork
Sybex CCNA
Chapter 5: Managing a Cisco Internetwork

2. Chapter 5 Objectives Cisco Router Components Boot Sequence
Configuration register
Backing up and restoring the IOS
Backing up and restoring the configuration
Cisco Discovery Protocol
Telnet
Resolving hostnames
Troubleshooting tools 2

3. Cisco Router Components
Bootstrap
Brings up the router during initialization
POST
Checks basic functionality; hardware & interfaces
ROM monitor
Manufacturing testing & troubleshooting
Mini-IOS
Loads Cisco IOS into flash memory
RAM
Holds packet buffers, routing tables, & software
Stores running-config

4. Cisco Router Components (cont)
ROM
Starts & maintains the router
Flash Memory
Holds Cisco IOS
Not erased when the router is reloaded
NVRAM
Holds router (& switch) configurations (startup-config)
Configuration Register
Controls how the router boots up

5. Boot Sequence 1: Router performs a POST
2: Bootstrap looks for & loads the Cisco IOS
3: IOS software looks for a valid configuration file
4: Startup-config file (from NVRAM) is loaded
If startup-config file is not found, the router will start the setup mode

6. Configuration Registers
16-bit software written into NVRAM
Loads from flash memory & looks for the startup-config file
Configuration Register Bits
16 bits read 15-0, from left to right
default setting: 0x2102
Register ,
Bit number
Binary
NOTE: 0x means the digits that follow are in hexadecimal
You read the numbers in the “Binary” (lower) line above as four groups of four bits each.
Each group reads across: “ ”, so in the binary line, the groups are:
= 2, = 1, = 0, and = 2
The entire row, therefore, reads “2102”

7. Configuration Registers (cont)
Bit number
Binary
The characters “0x” indicates that the following digits are in hexadecimal.
Note that with reference to the config register, each hex character translates as a separate “nibble”, or a 4-bit, binary number.
This is why the hex 0x2102 translates as the “Binary” line above

8. Configuration Registers (cont)
The lowest four bits of the configuration register (bits 3, 2, 1, and 0) form the boot field. The order in which the switch/router looks for system bootstrap information depends on the boot field setting in the configuration register.
When the boot field is set to either 0 or 1 ( or ), the system ignores any boot instructions in the system configuration file and the following occurs:
When the boot field is set to 1 you will boot from an IOS image stored in ROM.
When the boot field is set to 0, you must boot the operating system manually by giving a boot command to the system bootstrap program, or ROM monitor (ROMmon mode).

9. Configuration Registers (full text)9

10. Checking the Register Value
Router#sh version
Cisco Internetwork Operating System Software
IOS ™ C2600 Software (C2600-I-M), Version 12.0(3)T3
RELEASE SOFTWARE (fc1)
[output cut]
Configuration register is 0x2102

11. Configuration Meanings

12. Boot Field Meanings (Config Register bits 00 – 03)

13. Changing the Configuration Register
Why would you want to change the config register? Several reasons:
to force the system into the ROM monitor mode
to select a boot source & default boot filename
to enable or disable the Break function
to set the console terminal baud rate
to load operating software from ROM
to enable booting from a TFTP server

14. Changing the Configuration Register
One way to change the config register is to use the command below:
Router(config)#config-register 0x0101
Router(config)#^Z
Router#sh ver
Configuration register is 0x2102 (will be 0x0101 at next reload)
The command displays both the current value of the config register as well as the value at the next reload.

15. Recovering Passwords 1: Boot the router
1(a): interrupt the boot sequence by performing a break
2: Change the configuration register to turn on bit 6 (0x2142)
3: Reload the router
4: Enter the privileged mode
5: Copy the startup-config to running-config
6: Change the password
7: Reset the configuration register to the default value
8: Reload the router
Note: You need physical access to the router to do this.

16. Recovering Passwords – (Step by step)
1: Boot the router & interrupt the boot sequence by performing a break using the Ctrl+Break key combination.
You may need to upgrade your version of hyper-terminal in order for this to work successfully.
(I’ve never had to do this, and I’ve used some pretty old versions of HyperTerminal; grain of salt here).

17. Recovering Passwords
2: Change the configuration register to turn on bit 6 (0x2142)
rommon>confreg 0x2142
You must reset or power cycle for new config to take effect
3: Reload the router
Type reset
The router will reload & ask if you want to enter setup mode
Answer NO
4: Enter the privileged mode
Router>enable
Router#

18. Recovering Passwords 5: Copy the startup-config to running-config
Router#copy startup-config running-config
6: Change the password
Router#config t
Router(config)#enable secret cisco
7: Reset the configuration register to the default value
Router(config)#config-register 0x2102
8: Reload the router

19. Backing up & Restoring the Cisco IOS
Before you upgrade…..
Copy the existing IOS to a TFTP host!
Verify Flash Memory
Router#sh flash
System flash directory:
File Length Name/status
c2500-js bin
[ bytes used, available, total]
16384K bytes of processor board System flash (Read ONLY)
Router#

20. Restoring or Upgrading the Cisco IOS
#1: Ensure you have good connectivity to the TFTP host
Router#ping
#2: Copy the IOS from the TFTP host to flash
Router#copy tftp flash
This copies the new IOS, currently in the default directory of the TFTP server, to NVRAM where it will become the operating system for the router, switch or other Cisco device being upgraded.
The TFTP host must have a default directory specified
Copying the IOS from a TFTP host to flash requires a router reboot
20 / 265

21. Backing up the Cisco IOS
#1: Ensure you have good connectivity to the TFPT host
Router#ping
#2: Copy the IOS from flash to the TFTP host
Router#copy flash tftp
This command copies the contents of flash (the old IOS version) to the TFTP host.
The TFTP host must have a default directory specified

22. Backing up the Configuration
1: Verify the Current Configuration
Router#sh run
2: Verify the Stored Configuration
Router#sh start
Verify available memory
3: Copy running-config to NVRAM
Router#copy run start
The configuration you are currently running becomes the config that you will now boot to, after copying it to NVRAM, the startup config.
4: Copy running-config to a TFTP host
Router#copy run tftp
A second backup

23. Restoring the Configuration
Used when…
You need to copy the startup-config to the running-config
Errors made in editing the running-config
Changes made at the TFTP host need to be copied to the running-config or startup-config
Router#copy tftp run or Router#copy tftp start
NOTE: The configuration file is ASCII. Any text editor will enable changes
Erasing the Configuration
Router#erase startup-config
Note: When the router reboots it will be in setup mode
See Supp Power Point 2 for recovering the Configuration using Xmodem:
“Download using Xmodem from rommon >”

24. Table 1 Network Prefixes for Cisco IFS URLs
Cisco IOS File System
Cisco has a file system called IFS that allows you to work with files and directories just as you would from a DOS prompt.
Some IFS commands use URLs as part of the command syntax.
This link is to “Cisco IOS File System Command Syntax”
Below are some tables showing examples of the IFS:
Table 1 Network Prefixes for Cisco IFS URLs
Prefix
Description
ftp:
Specifies a File Transfer Protocol (FTP) network server.
rcp:
Specifies an remote copy protocol (rcp) network server.
tftp:
Specifies a TFTP server.

25. Table 2 File ID Suffixes for Cisco IFS URLs
Cisco IOS File System
Table 2 File ID Suffixes for Cisco IFS URLs
Prefix
Suffix Options
ftp:
For example:
ftp://network-config (prefix://filename)
rcp:
tftp:
tftp:[[//location]/directory]/filename

26. Cisco IOS File System Prefix Description
Table 3: File System Prefixes for Cisco IFS URLs 
Prefix
Description
bootflash:
Bootflash memory.
disk0:
Rotating disk media.
flash: [partition-#]
Flash memory. This prefix is available on all platforms
flh:
Flash load helper log files.
null:
Null destination for copies. Copy a remote file to null to find its size.
nvram:
NVRAM. This is the default location for the running-configuration file.
slavebootflash:
Internal Flash on slave RSP card of a router configured with 2 RSPs.
slavenvram:
NVRAM on a slave RSP card.
slaveslot0:
First PCMCIA card on a slave RSP card.
slaveslot1:
Second PCMCIA card on a slave RSP card.
slot0:
First PCMCIA Flash memory card.
slot1:
Second PCMCIA Flash memory card.
xmodem:
Obtain the file from a network machine using the Xmodem protocol.
ymodem:
Obtain the file from a network machine using the Ymodem protocol.

27. Cisco IOS File System
The limitations of the IFS are, of course, that it is simply a tool to carry out some fairly basic tasks: copying files, transferring files, working with specific types of memory found in routers and switches, etc. But within these parameters, it does have some benefits:
One of the benefits is that the file system’s user interface is universal — it’s not platform specific. You get to use the same syntax for all your commands on all of your routers.
Another benefit is that it cuts down on all those obligatory prompts for a lot of the commands.
If you want to enter a command, all you have to do is type all the necessary info straight into the command line.
if you want to copy a file to an FTP server, all you do is:
first indicate where the desired source file is on your router
pinpoint where the destination file is on the FTP server
determine the username and password you’re going to use, and
type it all in on one line!

28. Using Cisco Discovery Protocol (CDP)
A Cisco proprietary protocol
Designed to collect information about directly attached & remote devices
Hardware information
Protocol information
Useful in troubleshooting & documenting the network

29. Getting CDP Timers & Holdtime Information
Configuration:
CDP Timer: How often CDP packets are transmitted to all active interfaces
CDP Holdtime: The amount of time that the device will hold packets received from neighbor devices
Router#sh cdp
Global CDP information
Sending CDP packets every 60 seconds
Sending a value of 180 seconds
Router#config t
Router(config)#cdp timer 90
Router(config)#cdp holdtime 240

30. Getting Neighbor Information
Shows information about directly connected devices
CDP packets are not passed through a Cisco switch
Can only see what is directly attached
Router#sh cdp nei (“nei” stands for “Neighbor”, i.e., “directly attached” devices). or
Router#sh cdp neighbor detail
Detailed information; hostname, IP address, etc

31. Getting Interface Traffic & Port Information
Interface Traffic Information:
CDP packets sent & received
Errors with CDP
Router# sh cdp traffic
Port & Interface Information:
Encapsulation on the line
Timer & Holdtime for each interface
Router# sh cdp interface

32. Using Telnet A virtual terminal protocol Part of the TCP/IP suite
Allows connections to remote devices
Gather information
Run programs
Note: The VTY passwords must be set on the routers in order for them to allow a telnet session.

33. Using Telnet Setting VTY passwords:
RouterB#config t - to global config mode
RouterB(config)#line vty to get to line-config mode, for telnet
RouterB(config)#login - sets the state to enter login PW
RouterB(config)#password cisco - set the login PW as “cisco”
RouterB(config)#^Z - brings you back to privileged mode
RouterA# entering just an IP addr tries telnet
Trying … Open
User Access Verification
Password:
RouterB>

34. Using Telnet Setting VTY password: Remember…. RouteBr#config t
RouterB(config)#line vty 0 4
RouterB(config)#login
RouterB(config)#password cisco
RouterB(config)#^Z
RouterA#
Trying … Open
User Access Verification
Password:
RouterB>
Remember….
VTY password is the user mode (>) password - not the enable mode (#) password
With no enable/enable secret password set, the following happens:
RouterB>en
% No password set
RouterB>
This equates to good security!
(in other words, with telnet, you MUST have a password set in order to access the utility!)

35. Telnet Commands Telnetting into Multiple Devices
Ctrl+Shift+6 (release) X
Checking Telnet Connections
Router#sh sessions
Checking Telnet Users
Router#sh users
Closing Telnet Sessions
RouterB>exit
RouterB>disconnect

36. Resolving Hostnames
To use a hostname rather than an IP address to connect to a remote host a device must be able to translate the hostname to an IP address
Build a host table on each router
Build a Domain Name System (DNS) server

37. Building a Host Table
Provides name resolution only on the router on which it is built
[ip host name tcp_port_number ip_address]u
Router(config)#ip host RouterB
Router(config)#ip host switch
Router#sh hosts
Default TCP port number: 23
Router#RouterB
RouterB#(Ctrl+Shift+6) (X)
Router#switch

38. Using DNS to Resolve Names
Used when you have many devices on your network
Making DNS work…
ip domain-lookup
Turned on by default
ip name-server
Sets the IP address of the DNS server (up to 6 each)
ip domain-name
Appends the domain name to the hostname
Ex: RouterA.neversail.navy.mil

39. Checking Network Connectivity
Ping
Displays the minimum, average, & maximum times it takes for a ping packet to find a specified system + return
Router#ping RouterB
Trace
Shows the path a packet takes to get to a remote device
Router#trace RouterB

40. Summary Go through all the written and review questions
Go through the answers with the class 40