Senior Acquisitions Editor: Kenyon Brown Development Editor: Kim Wimpsett

copy current to starting

B.

Switch#

copy starting to running

C.

Switch(config)#

copy running-config startup-config

D.

Switch#

copy run start

12.  You try to telnet into SF from router Corp and receive this message:

Corp#

telnet SF

Trying SF (10.0.0.1)...Open

Password required, but none set

[Connection to SF closed by foreign host]

Corp#

Which of the following sequences will address this problem correctly?

A.

Corp(config)#line console 0

Corp(config-line)#password password

Corp(config-line)#login

B.

SF config)#line console 0

SF(config-line)#enable secret password

SF(config-line)#login

C.

Corp(config)#line vty 0 4

Corp(config-line)#password password

Corp(config-line)#login

D.

SF(config)#line vty 0 4

SF(config-line)#password password

SF(config-line)#login

13.  Which command will delete the contents of NVRAM on a switch?

A.

delete NVRAM

B.

delete startup-config

C.

erase flash

D.

erase startup-config

E.

erase start

14.  What is the problem with an interface if you type

show interface g0/1

and receive the following message?

Gigabit 0/1 is administratively down, line protocol is down

A.  The keepalives are different times.

B.  The administrator has the interface shut down.

C.  The administrator is pinging from the interface.

D.  No cable is attached.

15.  Which of the following commands displays the configurable

parameters and statistics of all interfaces on a switch?

A.

show running-config

B.

show startup-config

C.

show interfaces

D.

show versions

16.  If you delete the contents of NVRAM and reboot the switch, what

mode will you be in?

A.  Privileged mode

B.  Global mode

C.  Setup mode

D.  NVRAM loaded mode

17.  You type the following command into the switch and receive the

following output:

Switch#

show fastethernet 0/1

^

% Invalid input detected at '^' marker.

Why was this error message displayed?

A.  You need to be in privileged mode.

B.  You cannot have a space between

fastethernet

and

0/1

.

C.  The switch does not have a FastEthernet 0/1 interface.

D.  Part of the command is missing.

18.  You type

Switch#sh r

and receive a

% ambiguous command

error. Why

did you receive this message?

A.  The command requires additional options or parameters.

B.  There is more than one

show

command that starts with the letter r.

C.  There is no

show

command that starts with r.

D.  The command is being executed from the wrong mode.

19.  Which of the following commands will display the current IP

addressing and the layer 1 and 2 status of an interface? (Choose two.)

A.

show version

B.

show interfaces

C.

show controllers

D.

show ip interface

E.

show running-config

20.  At which layer of the OSI model would you assume the problem is if

you type

show interface serial 1

and receive the following message?

Serial1 is down, line protocol is down

A.  Physical layer

B.  Data Link layer

C.  Network layer

D.  None; it is a router problem.

Chapter 7

Managing a Cisco Internetwork

The following ICND1 exam topics are covered in

this chapter:

2.0 LAN Switching Technologies

2.6 Configure and verify Layer 2 protocols

2.6.a Cisco Discovery Protocol

2.6.bLLDP

4.0 Infrastructure Services

4.1 Describe DNS lookup operation

4.2 Troubleshoot client connectivity issues involving DNS

4.3 Configure and verify DHCP on a router (excluding static

reservations)

4.3.a Server

4.3.b Relay

4.3.c Client

4.3.d TFTP, DNS, and gateway options

4.4 Troubleshoot client- and router-based DHCP connectivity

issues

4.5 Configure and verify NTP operating in client/server mode

5.0 Infrastructure Management

5.1 Configure and verify device-monitoring using syslog

5.2 Configure and verify device management

5.2.a Backup and restore device configuration

5.2.b Using Cisco Discovery Protocol and LLDP for device

discovery

5.2.d Logging

5.2.e Timezone

5.2.f Loopback

Here in Chapter 7, I’m going to show you how

to manage Cisco routers and switches on an internetwork. You’ll be

learning about the main components of a router, as well as the router

boot sequence. You’ll also find out how to manage Cisco devices by using

the

copy

command with a TFTP host and how to configure DHCP and

NTP, plus you’ll get a survey of the Cisco Discovery Protocol (CDP). I’ll

also show you how to resolve hostnames.

I’ll wrap up the chapter by guiding you through some important Cisco

IOS troubleshooting techniques to ensure that you’re well equipped with

these key skills.

To find up-to-the minute updates for this chapter, please see

www.lammle.com/ccna

or the book’s web page at

www.sybex.com/go/ccna

.

The Internal Components of a Cisco Router and

Switch

Unless you happen to be really savvy about the inner and outer workings

of all your car’s systems and its machinery and how all of that technology

works together, you’ll take it to someone who does know how to keep it

maintained, figure out what’s wrong when it stops running, and get it up

and running again. It’s the same deal with Cisco networking devices—you

need to know all about their major components, pieces, and parts as well

as what they all do and why and how they all work together to make a

network work. The more solid your knowledge, the more expert you are

about these things and the better equipped you’ll be to configure and

troubleshoot a Cisco internetwork. Toward that goal, study

Table 7.1

for

an introductory description of a Cisco router’s major components.

TABLE 7.1

Cisco router components

Component Description

Bootstrap

Stored in the microcode of the ROM, the bootstrap is

used to bring a router up during initialization. It boots

the router up and then loads the IOS.

POST (power-

on self-test)

Also stored in the microcode of the ROM, the POST is

used to check the basic functionality of the router

hardware and determines which interfaces are present.

ROM monitor Again, stored in the microcode of the ROM, the ROM

monitor is used for manufacturing, testing, and

troubleshooting, as well as running a mini-IOS when the

IOS in flash fails to load.

Mini-IOS

Called the RXBOOT or bootloader by Cisco, the mini-IOS

is a small IOS in ROM that can be used to bring up an

interface and load a Cisco IOS into flash memory. The

mini-IOS can also perform a few other maintenance

operations.

RAM

(random

access

memory)

Used to hold packet buffers, ARP cache, routing tables,

and also the software and data structures that allow the

router to function. Running-config is stored in RAM, and

most routers expand the IOS from flash into RAM upon

boot.

ROM (read-

only

memory)

Used to start and maintain the router. Holds the POST

and the bootstrap program as well as the mini-IOS.

Flash

memory

Stores the Cisco IOS by default. Flash memory is not

erased when the router is reloaded. It is EEPROM

(electronically erasable programmable read-only

memory) created by Intel.

NVRAM

(nonvolatile

RAM)

Used to hold the router and switch configuration.

NVRAM is not erased when the router or switch is

reloaded. Does not store an IOS. The configuration

register is stored in NVRAM.

Configuration

register

Used to control how the router boots up. This value can

be found as the last line of the

show version

command

output and by default is set to 0x2102, which tells the

router to load the IOS from flash memory as well as to

load the configuration from NVRAM.

The Router and Switch Boot Sequence

When a Cisco device boots up, it performs a series of steps, called the

boot sequence, to test the hardware and load the necessary software. The

boot sequence comprises the following steps, as shown in

Figure 7.1

:

1.  The IOS device performs a POST, which tests the hardware to verify

that all components of the device are present and operational. The

post takes stock of the different interfaces on the switch or router, and

it’s stored in and runs from read-only memory (ROM).

2.  The bootstrap in ROM then locates and loads the Cisco IOS software

by executing programs responsible for finding where each IOS

program is located. Once they are found, it then loads the proper files.

By default, the IOS software is loaded from flash memory in all Cisco

devices.

FIGURE 7.1

Router bootup process

3.  The IOS software then looks for a valid configuration file stored in

NVRAM. This file is called startup-config and will be present only if

an administrator has copied the running-config file into NVRAM.

4.  If a startup-config file is found in NVRAM, the router or switch will

copy it, place it in RAM, and name the file the running-config. The

device will use this file to run, and the router/switch should now be

operational. If a startup-config file is not in NVRAM, the router will

broadcast out any interface that detects carrier detect (CD) for a TFTP

host looking for a configuration, and when that fails (typically it will

fail—most people won’t even realize the router has attempted this

process), it will start the setup mode configuration process.

The default order of an IOS loading from a Cisco device begins

with flash, then TFTP server, and finally, ROM.

Backing Up and Restoring the Cisco

Configuration

Any changes that you make to the configuration are stored in the

running-config file. And if you don’t enter a

copy run start

command

after you make a change to running-config, that change will totally

disappear if the device reboots or gets powered down. As always, backups

are good, so you’ll want to make another backup of the configuration

information just in case the router or switch completely dies on you. Even

if your machine is healthy and happy, it’s good to have a backup for

reference and documentation reasons!

Next, I’ll cover how to copy the configuration of a router to a TFTP server

as well as how to restore that configuration.

Backing Up the Cisco Configuration

To copy the configuration from an IOS device to a TFTP server, you can

use either the

copy running-config tftp

or the

copy startup-config tftp

command. Either one will back up the router configuration that’s

currently running in DRAM or one that’s stored in NVRAM.

Verifying the Current Configuration

To verify the configuration in DRAM, use the

show running-config

command (

sh run

for short) like this:

Router#

show running-config

Building configuration...

Current configuration : 855 bytes

!

version 15.0

The current configuration information indicates that the router is

running version 15.0 of the IOS.

Verifying the Stored Configuration

Next, you should check the configuration stored in NVRAM. To see this,

use the

show startup-config

command (

sh start

for short) like this:

Router#

sh start

Using 855 out of 524288 bytes

!

! Last configuration change at 04:49:14 UTC Fri Mar 5 1993

!

version 15.0

The first line shows you how much room your backup configuration is

taking up. Here, we can see that NVRAM is about 524 KB and that only

855 bytes of it are being used. But memory is easier to reveal via the

show

version

command when you’re using an ISR router.

If you’re not sure that the files are the same and the running-config file is

what you want to go with, then use the

copy running-config startup-

config

command. This will help you ensure that both files are in fact the

same. I’ll guide you through this in the next section.

Copying the Current Configuration to NVRAM

By copying running-config to NVRAM as a backup, as shown in the

following output, you ensure that your running-config will always be

reloaded if the router gets rebooted. Starting in the 12.0 IOS, you’ll be

prompted for the filename you want to use:

Router#

copy running-config startup-config

Destination filename [startup-config]?

[enter]

Building configuration...

[OK]

The reason the filename prompt appears is that there are now so many

options you can use when using the

copy

command—check it out:

Router#

copy running-config ?

flash: Copy to flash: file system

ftp: Copy to ftp: file system

http: Copy to http: file system

https: Copy to https: file system

null: Copy to null: file system

nvram: Copy to nvram: file system

rcp: Copy to rcp: file system

running-config Update (merge with) current system configuration

scp: Copy to scp: file system

startup-config Copy to startup configuration

syslog: Copy to syslog: file system

system: Copy to system: file system

tftp: Copy to tftp: file system

tmpsys: Copy to tmpsys: file system

Copying the Configuration to a TFTP Server

Once the file is copied to NVRAM, you can make a second backup to a

TFTP server by using the

copy running-config tftp

command, or

copy

run tftp

for short. I’m going to set the hostname to

Todd

before I run this

command:

Todd#

copy running-config tftp

Address or name of remote host []?

10.10.10.254

Destination filename [todd-confg]?

!!

776 bytes copied in 0.800 secs (970 bytes/sec)

If you have a hostname already configured, the command will

automatically use the hostname plus the extension

-confg

as the name of

the file.

Restoring the Cisco Configuration

What do you do if you’ve changed your running-config file and want to

restore the configuration to the version in the startup-config file? The

easiest way to get this done is to use the

copy startup-config running-

config

command, or

copy start run

for short, but this will work only if

you copied running-config into NVRAM before you made any changes! Of

course, a reload of the device will work too!

If you did copy the configuration to a TFTP server as a second backup,

you can restore the configuration using the

copy tftp running-config

command (

copy tftp run

for short), or the

copy tftp startup-config

command (

copy tftp start

for short), as shown in the following output.

Just so you know, the old command we used to use for this is

config net

:

Todd#

copy tftp running-config

Address or name of remote host []?

10.10.10.254

Source filename []?

todd-confg

Destination filename[running-config]?

[enter]

Accessing tftp://10.10.10.254/todd-confg...

Loading todd-confg from 10.10.10.254 (via FastEthernet0/0):

!!

[OK - 776 bytes]

776 bytes copied in 9.212 secs (84 bytes/sec)

Todd#

*Mar 7 17:53:34.071: %SYS-5-CONFIG_I: Configured from

tftp://10.10.10.254/todd-confg by console

Okay that the configuration file is an ASCII text file . . . meaning that

before you copy the configuration stored on a TFTP server back to a

router, you can make changes to the file with any text editor.

Remember that when you copy or merge a configuration from

a TFTP server to a freshly erased and rebooted router’s RAM, the

interfaces are shut down by default and you must manually enable

each interface with the

no shutdown

command.

Erasing the Configuration

To delete the startup-config file on a Cisco router or switch, use the

command

erase startup-config

, like this:

Todd#

erase startup-config

Erasing the nvram filesystem will remove all configuration files!

Continue? [confirm]

[enter]

[OK]

Erase of nvram: complete

*Mar 7 17:56:20.407: %SYS-7-NV_BLOCK_INIT: Initialized the

geometry of nvram

Todd#

reload

System configuration has been modified. Save? [yes/no]:

n

Proceed with reload? [confirm]

[enter]

*Mar 7 17:56:31.059: %SYS-5-RELOAD: Reload requested by console.

Reload Reason: Reload Command.

This command deletes the contents of NVRAM on the switch and router.

If you type

reload

while in privileged mode and say no to saving changes,

the switch or router will reload and come up into setup mode.

Configuring DHCP

We went over DHCP in Chapter 3, “Introduction to TCP/IP,” where I

described how it works and what happens when there’s a conflict. At this

point, you’re ready to learn how to configure DHCP on Cisco’s IOS as well

as how to configure a DHCP forwarder for when your hosts don’t live on

the same LAN as the DHCP server. Do you remember the four-step

process hosts used to get an address from a server? If not, now would be a

really great time to head back to Chapter 3 and thoroughly review that

before moving on with this!

To configure a DHCP server for your hosts, you need the following

information at minimum:

Network and mask for each LAN Network ID, also called a scope.

All addresses in a subnet can be leased to hosts by default.

Reserved/excluded addresses Reserved addresses for printers,

servers, routers, etc. These addresses will not be handed out to hosts. I

usually reserve the first address of each subnet for the router, but you

don’t have to do this.

Default router This is the router’s address for each LAN.

DNS address A list of DNS server addresses provided to hosts so

they can resolve names.

Here are your configuration steps:

1.  Exclude the addresses you want to reserve. The reason you do this

step first is because as soon as you set a network ID, the DHCP service

will start responding to client requests.

2.  Create your pool for each LAN using a unique name.

3.  Choose the network ID and subnet mask for the DHCP pool that the

server will use to provide addresses to hosts.

4.  Add the address used for the default gateway of the subnet.

5.  Provide the DNS server address(es).

6.  If you don’t want to use the default lease time of 24 hours, you need to

set the lease time in days, hours, and minutes.

I’ll configure the switch in

Figure 7.2

to be the DHCP server for the Sales

wireless LAN.

FIGURE 7.2

DHCP configuration example on a switch

Understand that this configuration could just have easily been placed on

the router in

Figure 7.2

. Here’s how we’ll configure DHCP using the

192.168.10.0/24 network ID:

Switch(config)#

ip dhcp excluded-address 192.168.10.1 192.168.10.10

Switch(config)#

ip dhcp pool Sales_Wireless

Switch(dhcp-config)#

network 192.168.10.0 255.255.255.0

Switch(dhcp-config)#

default-router 192.168.10.1

Switch(dhcp-config)#

dns-server 4.4.4.4

Switch(dhcp-config)#

lease 3 12 15

Switch(dhcp-config)#

option 66 ascii tftp.lammle.com

First, you can see that I reserved 10 addresses in the range for the router,

servers, and printers, etc. I then created the pool named Sales_Wireless,

added the default gateway and DNS server, and set the lease to 3 days, 12

hours, and 15 minutes (which isn’t really significant because I just set it

that way for demonstration purposes). Lastly, I provided an example on

you how you would set option 66, which is sending a TFTP server address

to a DHCP client. Typically used for VoIP phones, or auto installs, and

needs to be listed as a FQDN. Pretty straightforward, right? The switch

will now respond to DHCP client requests. But what happens if we need

to provide an IP address from a DHCP server to a host that’s not in our

broadcast domain, or if we want to receive a DHCP address for a client

from a remote server?