Senior Acquisitions Editor: Kenyon Brown Development Editor: Kim Wimpsett

copy running-config startup-config

Destination filename [startup-config]? [

press enter]

Building configuration...

[OK]

Todd#

Building configuration...

When you see a question with an answer in

[]

, it means that if you just

press Enter, you’re choosing the default answer.

Also, when the command asks for the destination filename, the default

answer is startup-config. The reason it asks is because you can copy the

configuration to pretty much anywhere you want. Take a look at the

output from my switch:

Todd#

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

vb: Copy to vb: file system

To reassure you, we’ll get deeper into how and where to copy files in

Chapter 7.

For now, you can view the files by typing

show running-config

or

show

startup-config

from privileged mode. The

sh run

command, which is a

shortcut for

show

​

running-config

, tells us that we’re viewing the current

configuration:

Todd#

sh run

Building configuration...

Current configuration : 855 bytes

!

! Last configuration change at 23:20:06 UTC Mon Mar 1 1993

!

version 15.0

[output cut]

The

sh start

command—one of the shortcuts for the

show startup-

config

​command—shows us the configuration that will be used the next

time the router is reloaded. It also tells us how much NVRAM is being

used to store the startup-config file. Here’s an example:

Todd#

sh start

Using 855 out of 524288 bytes

!

! Last configuration change at 23:20:06 UTC Mon Mar 1 1993

!

version 15.0

[output cut]

But beware—if you try and view the configuration and see

Todd#

sh start

startup-config is not present

you have not saved your running-config to NVRAM, or you’ve deleted the

backup configuration! Let me talk about just how you would do that now.

Deleting the Configuration and Reloading the Device

You can delete the startup-config file by using the

erase startup-config

command:

Todd#

erase start

% Incomplete command.

First, notice that you can no longer use the shortcut commands for

erasing the backup configuration. This started in IOS 12.4 with the ISR

routers.

Todd#

erase startup-config

Erasing the nvram filesystem will remove all configuration files!

Continue? [confirm]

[OK]

Erase of nvram: complete

Todd#

*Mar 5 01:59:45.206: %SYS-7-NV_BLOCK_INIT: Initialized the

geometry of nvram

Todd#

reload

Proceed with reload? [confirm]

Now if you reload or power the router down after using the

erase

startup-

​

config

command, you’ll be offered setup mode because there’s

no configuration saved in NVRAM. You can press Ctrl+C to exit setup

mode at any time, but the

reload

command can only be used from

privileged mode.

At this point, you shouldn’t use setup mode to configure your router. So

just say

no

to setup mode, because it’s there to help people who don’t

know how to use the command line interface (CLI), and this no longer

applies to you. Be strong—you can do it!

Verifying Your Configuration

Obviously,

show running-config

would be the best way to verify your

configuration and

show startup-config

would be the best way to verify

the configuration that’ll be used the next time the router is reloaded—

right?

Well, once you take a look at the running-config, if all appears well, you

can verify your configuration with utilities like Ping and Telnet. Ping is a

program that uses ICMP echo requests and replies, which we covered in

Chapter 3. For review, Ping sends a packet to a remote host, and if that

host responds, you know that it’s alive. But you don’t know if it’s alive and

also well; just because you can ping a Microsoft server does not mean you

can log in! Even so, Ping is an awesome starting point for troubleshooting

an internetwork.

Did you know that you can ping with different protocols? You can, and

you can test this by typing

ping ?

at either the router user-mode or

privileged-mode prompt:

Todd#

ping ?

WORD Ping destination address or hostname

clns CLNS echo

ip IP echo

ipv6 IPv6 echo

tag Tag encapsulated IP echo

If you want to find a neighbor’s Network layer address, either you go

straight to the router or switch itself or you can type

show cdp entry *

protocol

to get the Network layer addresses you need for pinging.

You can also use an extended ping to change the default variables, as

shown here:

Todd#

ping

Protocol [ip]:

Target IP address:

10.1.1.1

Repeat count [5]:

% A decimal number between 1 and 2147483647.

Repeat count [5]:

5000

Datagram size [100]:

% A decimal number between 36 and 18024.

Datagram size [100]:

1500

Timeout in seconds [2]:

Extended commands [n]:

y

Source address or interface:

FastEthernet 0/1

Source address or interface:

Vlan 1

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5000, 1500-byte ICMP Echos to 10.1.1.1, timeout is 2

seconds:

Packet sent with a source address of 10.10.10.1

Notice that by using the question mark, I was able to determine that

extended ping allows you to set the repeat count higher than the default

of 5 and the datagram size larger. This raises the MTU and allows for a

more accurate testing of throughput. The source interface is one last

important piece of information I’ll pull out of the output. You can choose

which interface the ping is sourced from, which is really helpful in certain

diagnostic situations. Using my switch to display the extended ping

capabilities, I had to use my only routed port, which is named VLAN 1, by

default.

However, if you want to use a different diagnostic port, you can create a

logical interface called a loopback interface as so:

Todd(config)#

interface loopback ?

<0-2147483647> Loopback interface number

Todd(config)#

interface loopback 0

*May 19 03:06:42.697: %LINEPROTO-5-UPDOWN: Line prot

changed state to ups

Todd(config-if)#

ip address 20.20.20.1 255.255.255.0

Now I can use this port for diagnostics, and even as my source port of my

ping or traceroute, as so:

Todd#

ping

Protocol [ip]:

Target IP address: 10.1.1.1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface:

20.20.20.1

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:

Packet sent with a source address of 20.20.20.1

The logical interface are great for diagnostics and for using them in our

home labs where we don’t have any real interfaces to play with, but we’ll

also use them in our OSPF configurations in ICND2.

Cisco Discovery Protocol (CDP) is covered in Chapter 7.

Traceroute uses ICMP with IP time to live (TTL) time-outs to track the

path a given packet takes through an internetwork. This is in contrast to

Ping, which just finds the host and responds. Traceroute can also be used

with multiple protocols. Check out this output:

Todd#

traceroute ?

WORD Trace route to destination address or hostname

aaa Define trace options for AAA events/actions/errors

appletalk AppleTalk Trace

clns ISO CLNS Trace

ip IP Trace

ipv6 IPv6 Trace

ipx IPX Trace

mac Trace Layer2 path between 2 endpoints

oldvines Vines Trace (Cisco)

vines Vines Trace (Banyan)

And as with ping, we can perform an extended traceroute using

additional parameters, typically used to change the source interface:

Todd#

traceroute

Protocol [ip]:

Target IP address:

10.1.1.1

Source address:

172.16.10.1

Numeric display [n]:

Timeout in seconds [3]:

Probe count [3]:

Minimum Time to Live [1]:

255

Maximum Time to Live [30]:

Type escape sequence to abort.

Tracing the route to 10.1.1.1

Telnet, FTP, and HTTP are really the best tools because they use IP at the

Network layer and TCP at the Transport layer to create a session with a

remote host. If you can telnet, ftp, or http into a device, you know that

your IP connectivity just has to be solid!

Todd#

telnet ?

WORD IP address or hostname of a remote system

Todd#

telnet 10.1.1.1

When you telnet into a remote device, you won't see console messages by

default. For example, you will not see debugging output. To allow console

messages to be sent to your Telnet session, use the terminal monitor

command, as shown on the SF router.

SF#

terminal monitor

From the switch or router prompt, you just type a hostname or IP address

and it will assume you want to telnet—you don’t need to type the actual

command,

telnet

.

Coming up, I’ll show you how to verify the interface statistics.

Verifying with the show interface Command

Another way to verify your configuration is by typing

show interface

commands, the first of which is the

show interface ?

command. Doing

this will reveal all the available interfaces to verify and configure.

The

show interfaces

command, plural, displays the

configurable parameters and statistics of all interfaces on a router.

This command comes in really handy when you’re verifying and

troubleshooting router and network issues.

The following output is from my freshly erased and rebooted 2811 router:

Router#

sh int ?

Async Async interface

BVI Bridge-Group Virtual Interface

CDMA-Ix CDMA Ix interface

CTunnel CTunnel interface

Dialer Dialer interface

FastEthernet FastEthernet IEEE 802.3

Loopback Loopback interface

MFR Multilink Frame Relay bundle interface

Multilink Multilink-group interface

Null Null interface

Port-channel Ethernet Channel of interfaces

Serial Serial

Tunnel Tunnel interface

Vif PGM Multicast Host interface

Virtual-PPP Virtual PPP interface

Virtual-Template Virtual Template interface

Virtual-TokenRing Virtual TokenRing

accounting Show interface accounting

counters Show interface counters

crb Show interface routing/bridging info

dampening Show interface dampening info

description Show interface description

etherchannel Show interface etherchannel information

irb Show interface routing/bridging info

mac-accounting Show interface MAC accounting info

mpls-exp Show interface MPLS experimental accounting

info

precedence Show interface precedence accounting info

pruning Show interface trunk VTP pruning information

rate-limit Show interface rate-limit info

status Show interface line status

summary Show interface summary

switching Show interface switching

switchport Show interface switchport information

trunk Show interface trunk information

| Output modifiers

The only “real” physical interfaces are FastEthernet, Serial, and Async—

the rest are all logical interfaces or commands you can use to verify with.

The next command is

show interface fastethernet 0/0

. It reveals the

hardware address, logical address, and encapsulation method as well as

statistics on collisions, as seen here:

Router#

sh int f0/0

FastEthernet0/0 is up, line protocol is up

Hardware is MV96340 Ethernet, address is 001a.2f55.c9e8 (bia

001a.2f55.c9e8)

Internet address is 192.168.1.33/27

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto Speed, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 00:02:07, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output

drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

16 packets output, 960 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Router#

You probably guessed that we’re going to go over the important statistics

from this output, but first, just for fun, I’ve got to ask you, which subnet is

FastEthernet 0/0 a member of and what’s the broadcast address and

valid host range?

I’m serious—you really have to be able to nail these things NASCAR-fast!

Just in case you didn’t, the address is 192.168.1.33/27. And I’ve gotta be

honest—if you don’t know what a /27 is at this point, you’ll need a miracle

to pass the exam! That or you need to actually read this book. (As a quick

reminder, a /27 is 255.255.255.224.) The fourth octet is a block size of 32.

The subnets are 0, 32, 64, etc.; the FastEthernet interface is in the 32

subnet; the broadcast address is 63; and the valid hosts are 33–62. All

good now?

If you struggled with any of this, please save yourself from

certain doom and get yourself back into Chapter 4, “Easy Subnetting,”

now! Read and reread it until you’ve got it dialed in!

Okay—back to the output. The preceding interface is working and looks to

be in good shape. The

show interfaces

command will show you if you’re

receiving errors on the interface, and it will also show you the maximum

transmission unit (MTU). MTU is the maximum packet size allowed to

transmit on that interface, bandwidth (BW) is for use with routing

protocols, and 255/255 means that reliability is perfect! The load is

1/255, meaning no load.

Continuing through the output, can you figure out the bandwidth of the

interface? Well, other than the easy giveaway of the interface being called

a “FastEthernet” interface, we can see that the bandwidth is 100000 Kbit,

which is 100,000,000. Kbit means to add three zeros, which is 100 Mbits

per second, or FastEthernet. Gigabit would be 1000000 Kbits per second.

Be sure you don’t miss the output errors and collisions, which show 0 in

my output. If these numbers are increasing, then you have some sort of

Physical or Data Link layer issue. Check your duplex! If you have one side

as half-duplex and one at full-duplex, your interface will work, albeit

really slow and those numbers will be increasing fast!

The most important statistic of the

show interface

command is the

output of the line and Data Link protocol status. If the output reveals that

FastEthernet 0/0 is up and the line protocol is up, then the interface is up

and running:

Router#

sh int fa0/0

FastEthernet0/0 is up, line protocol is up

The first parameter refers to the Physical layer, and it’s up when it

receives carrier detect. The second parameter refers to the Data Link

layer, and it looks for keepalives from the connecting end. Keepalives are

important because they’re used between devices to make sure

connectivity hasn’t been dropped.

Here’s an example of where your problem will often be found—on serial

interfaces:

Router#

sh int s0/0/0

Serial0/0 is up, line protocol is down

If you see that the line is up but the protocol is down, as displayed here,

you’re experiencing a clocking (keepalive) or framing problem—possibly

an encapsulation mismatch. Check the keepalives on both ends to make

sure they match. Make sure that the clock rate is set, if needed, and that

the encapsulation type is equal on both ends. The preceding output tells

us that there’s a Data Link layer problem.

If you discover that both the line interface and the protocol are down, it’s

a cable or interface problem. The following output would indicate a

Physical layer problem:

Router#

sh int s0/0/0

Serial0/0 is down, line protocol is down

As you’ll see next, if one end is administratively shut down, the remote

end would present as down and down:

Router#

sh int s0/0/0

Serial0/0 is administratively down, line protocol is down

To enable the interface, use the command

no shutdown

from interface

configuration mode.

The next

show interface serial 0/0/0

command demonstrates the serial

line and the maximum transmission unit (MTU)—1,500 bytes by default.

It also shows the default bandwidth (BW) on all Cisco serial links, which

is 1.544 Kbps. This is used to determine the bandwidth of the line for

routing protocols like EIGRP and OSPF. Another important configuration

to notice is the keepalive, which is 10 seconds by default. Each router

sends a keepalive message to its neighbor every 10 seconds, and if both

routers aren’t configured for the same keepalive time, it won’t work!

Check out this output:

Router#

sh int s0/0/0

Serial0/0 is up, line protocol is up

Hardware is HD64570

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set, keepalive set

(10 sec)

Last input never, output never, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored,

0 abort

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 16 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

DCD=down DSR=down DTR=down RTS=down CTS=down

You can clear the counters on the interface by typing the command

clear

counters

:

Router#

clear counters ?

Async Async interface

BVI Bridge-Group Virtual Interface

CTunnel CTunnel interface

Dialer Dialer interface

FastEthernet FastEthernet IEEE 802.3

Group-Async Async Group interface

Line Terminal line

Loopback Loopback interface

MFR Multilink Frame Relay bundle interface

Multilink Multilink-group interface

Null Null interface

Serial Serial

Tunnel Tunnel interface

Vif PGM Multicast Host interface

Virtual-Template Virtual Template interface

Virtual-TokenRing Virtual TokenRing

Router#

clear counters s0/0/0

Clear "show interface" counters on this interface

[confirm]

[enter]

Router#

00:17:35: %CLEAR-5-COUNTERS: Clear counter on interface

Serial0/0/0 by console

Router#

Troubleshooting with the show interfaces Command

Let’s take a look at the output of the

show interfaces

command one more

time before I move on. There are some statistics in this output that are

important for the Cisco objectives.

275496 packets input, 35226811 bytes, 0 no buffer

Received 69748 broadcasts (58822 multicasts)