Rizal Technological University

College of Engineering
Department of Electronics Engineering

DATA COMMUNICATION LAB (COM04L)

ACTIVITY 3

NAME/S: ________________________ _______________________________

DATE PERFORMED: ________________ DATE SUBMITTED: ________________

DAY/TIME/: _____________________ INSTRUCTOR: ____________________

Status Check Evaluation Criteria Poor Fair Good Excellent

Reasoning
Advance
Accuracy
Completeness
On Time
Analytical Ability
Late Neatness of Work

Remarks: _____________________________________________________

___________________________________________________

Rating Signature

Date
 Lab Worksheet 3
Basic Switch Configuration

I. Objective

In this lab, you will examine and configure a standalone LAN switch. Although a switch performs
basic functions in its default out-of-the-box condition, there are a number of parameters that a network
administrator should modify to ensure a secure and optimized LAN. This lab introduces you to the basics
of switch configuration.

II. Discussion of the Theory

Recall that with shared Ethernet networks using hubs, many hosts are connected to a single broadcast
and collision domain. In other words, shared Ethernet media operates at OSI Layer 1.

Each host must share the available bandwidth with every other connected host. When more than one
host tries to talk at one time, a collision occurs, and everyone must back off and wait to talk again. This
forces every host to operate in half-duplex mode, by either talking or listening at any given time. In addition,
when one host sends a frame, all connected hosts hear it. When one host generates a frame with errors,
everyone hears that, too.

At its most basic level, an Ethernet switch provides isolation from other connected hosts in
several ways:

• The collision domain's scope is severely limited. On each switch port, the collision domain
consists of the switch port itself and the devices directly connected to that port—either a single
host or if a shared-media hub is connected, the set of hosts connected to the hub.
• Host connections can operate in full-duplex mode because there is no contention on the media.
Hosts can talk and listen at the same time.
• Bandwidth is no longer shared. Instead, each switch port offers dedicated bandwidth across a
switching fabric to another switch port. (These connections change dynamically.)
• Errors in frames are not propagated. Each frame received on a switch port is checked for errors.
Good frames are regenerated when they are forwarded or transmitted. This is known as store-
and-forward switching technology, where packets are received, stored for inspection, and then
forwarded.
• You can limit broadcast traffic to a volume threshold.
• Other types of intelligent filtering or forwarding become possible.

The switch builds and maintains a table, which is called a MAC table. This table matches a
destination MAC address with the port that is used to connect to a node. For each incoming frame, the
destination MAC address in the frame header is compared to the list of addresses in the MAC table.
Switches then use MAC addresses as they decide whether to filter, forward, or flood frames.

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III. Lab Exercise

where: xx – pair number

TASK 1: VERIFY THE DEFAULT SWITCH CONFIGURATION

Switch>enable
Switch#
Notice that the prompt changed in the configuration to reflect privileged EXEC mode.

Step 1: Examine the current switch configuration.

Examine the current running configuration file.

Switch# show running-config

How many Fast Ethernet interfaces does the switch have? _______________________
How many Gigabit Ethernet interfaces does the switch have? _____________________
What is the range of values shown for the vty lines? ____________________________

Step 2: Examine the current contents of NVRAM:

Switch# show startup-config

startup-config is not present

Why does the switch give this response?
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________

Step 3: Examine the characteristics of the virtual interface VLAN1:

Switch# show interface vlan1

Is there an IP address set on the switch? __________________________________

What is the MAC address of this virtual switch interface? ______________________
Is this interface up? ___________________________________________________
Now view the IP properties of the interface:

Switch#show ip interface vlan1

What output do you see?

_____________________________________________________________________________

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Step 4: Display Cisco IOS information.
Examine the following version information that the switch reports.

Switch#show version

What is the Cisco IOS version that the switch is running? _______________________
What is the system image filename? _______________________________________
What is the base MAC address of this switch? _______________________________

Step 5: Examine the Fast Ethernet interfaces.

Examine the default properties of the Fast Ethernet interface used by PC1.

Switch#show interface fastethernet 0/18

Is the interface up or down? ______________________________________

What event would make an interface go up? _________________________
What is the MAC address of the interface? __________________________
What is the speed and duplex setting of the interface? _________________

Step 6: Examine VLAN information.

Examine the default VLAN settings of the switch.

Switch#show vlan

What is the name of VLAN 1? _____________________________________

Which ports are in this VLAN? _____________________________________
Is VLAN 1 active? _______________________________________________
What type of VLAN is the default VLAN? _____________________________

TASK 2: CREATE A BASIC SWITCH CONFIGURATION

Step 1: Assign a name to the switch.

In the last step of the previous task, you configured the hostname.
Here's a review of the commands used.
Switch#config t !shortcut for configure terminal
Swicth (config)#hostname S1
S1(config)#exit
S1#

Step 2: Set the access passwords.

Enter config-line mode for the console. Set the login password to cisco.
Also configure the vty lines 0 to 15 with the password cisco.

S1#configure terminal

Enter the configuration commands, one for each line. When you are finished, return to global
configuration mode by entering the exit command or pressing Ctrl-Z.
S1(config)#line console 0
S1(config-line)#password cisco
S1(config-line)#login
S1(config-line)#line vty 0 15
S1(config-line)#password cisco
S1(config-line)#login
S1(config-line)#exit
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 Why is the login command required?
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________

Step 3: Set the command mode passwords.

Set the enable secret password to class. This password protects access to privileged EXEC
mode.

S1(config)#enable secret class

Step 4: Configure the Management IP address of the switch.

Before you can manage S1 remotely from PC1, you need to assign the switch an IP address. The
default configuration on the switch is to have the management of the switch controlled through
VLAN 1.
However, a best practice for basic switch configuration is to change the management VLAN to a
VLAN other than VLAN 1. The selection of VLAN xx is arbitrary and in no way implies you should
always use VLAN xx.

First, you will create the new VLAN xx on the switch. Then you will set the IP address of the
switch to 172.17.xx.11 with a subnet mask of 255.255.255.0 on the internal virtual interface VLAN
xx.
S1(config)#vlan xx
S1(config-vlan)#exit
S1(config)#interface vlanxx
%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlanxx, changed state to down
S1(config-if)#ip address 172.17. xx.11 255.255.255.0
S1(config-if)#no shutdown
S1(config-if)#exit
S1(config)#

Notice that the VLAN xx interface is in the down state even though you entered the command no
shutdown. The interface is currently down because no switch ports are assigned to VLAN xx.
Assign all user ports to VLAN xx.

S1(config)#interface range fa0/1 – 24

S1(config-if-range)#switchport access vlan xx
S1(config-if-range)#exit
S1(config-if-range)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlanxx, changed state to up

Notice in the above output that VLAN 1 interface goes down because none of the ports are
assigned to VLAN 1. After a few seconds, VLAN xx will come up because at least one port is now
assigned to VLAN xx.

Step 5: Set the switch default gateway.

S1 is a layer 2 switch, so it makes forwarding decisions based on the Layer 2 header. If multiple
networks are connected to a switch, you need to specify how the switch forwards the internetwork
frames, because the path must be determined at Layer 3. This is done by specifying a default
gateway address that points to a router or Layer 3 switch. Although this activity does not include
an external IP gateway, assume that you will eventually connect the LAN to a router for external
access. Assuming that the LAN interface on the router is 172.17.xx.1, set the default gateway for
the switch.
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 S1(config)#ip default-gateway 172.17. xx.1
S1(config)#exit

Step 6: Verify the management LANs settings.

Verify the interface settings on VLAN xx.

S1#show interface vlan xx

What is the bandwidth on this interface? ______________________________________

What are the VLAN states? VLAN1 is ______________ Line protocol is ______________
What is the queuing strategy? ____________________

Step 7: Configure the IP address and default gateway for PC1.

Set the IP address of PC1 to 172.17.xx.21, with a subnet mask of 255.255.255.0. Configure a
default gateway of 172.17.xx.11

Step 8: Verify connectivity.

To verify the host and switch are correctly configured, ping the IP address of the switch
(172.17.xx.11) from PC1.
Was the ping successful? ________________________
If not, troubleshoot the switch and host configuration. Note that this may take a couple of tries for
the pings to succeed.
Step 9: Configure the port speed and duplex settings for a Fast Ethernet interface.
Configure the duplex and speed settings on Fast Ethernet 0/18. Use the end command to return
to privileged EXEC mode when finished.

S1#configure terminal
S1(config)#interface fastethernet 0/18
S1(config-if)#speed 100
S1(config-if)#duplex full
S1(config-if)#end
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/18, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlanxx, changed state to down
%LINK-3-UPDOWN: Interface FastEthernet0/18, changed state to down
%LINK-3-UPDOWN: Interface FastEthernet0/18, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/18, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlanxx, changed state to up

The line protocol for both interface FastEthernet 0/18 and interface VLAN xx will temporarily go
down. The default on the Ethernet interface of the switch is auto-sensing, so it automatically
negotiates optimal settings. You should set duplex and speed manually only if a port must
operate at a certain speed and duplex mode. Manually configuring ports can lead to duplex
mismatches, which can significantly degrade performance.
Verify the new duplex and speed settings on the Fast Ethernet interface.

S1#show interface fastethernet 0/18

Step 10: Save the configuration.

You have completed the basic configuration of the switch. Now back up the running configuration
file to NVRAM to ensure that the changes made will not be lost if the system is rebooted or loses
power.

S1#copy running-config startup-config

Destination filename [startup-config]?[Enter] Building configuration...
[OK]
S1#
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TASK 3: MANAGING THE MAC ADDRESS TABLE

Step 1: Record the MAC addresses of the hosts.

Determine and record the Layer 2 (physical) addresses of the PC network interface cards using
the following commands:
Click the PC > Device Tab > Command prompt > type ipconfig /all
PC1: ____________________________________________
PC2: ____________________________________________

Step 2: Determine the MAC addresses that the switch has learned.
Display the MAC addresses using the show mac-address-table command in privileged EXEC
mode.

S1#show mac-address-table

How many dynamic addresses are there? _______________________________________

How many MAC addresses are there in total? ____________________________________
Do the dynamic MAC addresses match the host MAC addresses? ____________________

Step 3: List the show mac-address-table options.

S1#show mac-address-table ?

How many options are available for the show mac-address-table command? ___________
Show only the MAC addresses from the table that were learned dynamically.

S1#show mac-address-table address <PC1 MAC here>

How many dynamic addresses are there? _________________

Step 4: Clear the MAC address table.

To remove the existing MAC addresses, use the clear mac-address-table command from
privileged EXEC mode.

S1#clear mac-address-table dynamic

Step 5: Verify the results.

Verify that the MAC address table was cleared.

S1#show mac-address-table

How many static MAC addresses are there?_________________________________________

How many dynamic addresses are there? __________________________________________

Step 6: Examine the MAC table again.

More than likely, an application running on your PC1 has already sent a frame out the NIC to S1.
Look at the MAC address table again in privileged EXEC mode to see if S1 has relearned the
MAC address for PC1

S1#show mac-address-table

How many dynamic addresses are there? ___________________________________________

Why did this change from the last display? __________________________________________

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 _____________________________________________________________________________
_____________________________________________________________________________
If S1 has not yet relearned the MAC address for PC1, ping the VLAN xx IP address of the switch
from PC1

Step 7: Set up a static MAC address.

To specify which ports a host can connect to, one option is to create a static mapping of the host
MAC address to a port. Set up a static MAC address on Fast Ethernet interface 0/18 using the
address that was recorded for PC1 in Step 1 of this task.

S1(config)#mac-address-table static <PC1 MAC> vlan xx interface fastethernet0/18

Step 8: Verify the results.

Verify the MAC address table entries.
S1#show mac-address-table
How many total MAC addresses are there? ______________________________________
How many static addresses are there? __________________________________________

TASK 4: CONFIGURING PORT SECURITY

Step 1: Configure a second host.

A second host is needed for this task. Set the IP address of PC2 to 172.17.xx.32, with a subnet
mask of 255.255.255.0 and a default gateway of 172.17.xx.11. Do not connect this PC to the
switch yet.

Step 2: Verify connectivity.

Verify that PC1 and the switch are still correctly configured by pinging the VLANxx IP address of
the switch from the host.
Were the pings successful? _____________________________________
If the answer is no, troubleshoot the host and switch configurations.

Step 3: Copy the host MAC addresses.

Write down the MAC addresses from Task 3
PC1: ____________________________________________
PC2: ____________________________________________

Step 4: Determine which MAC addresses that the switch has learned.
Display the learned MAC addresses using the show mac-address-table command in privileged
EXEC mode.

S1#show mac-address-table

How many dynamic addresses are there? ___________________________________

Do the MAC addresses match the host MAC addresses? _______________________

Step 5: List the port security options.

Explore the options for setting port security on interface Fast Ethernet 0/18.

S1# configure terminal

S1(config)#interface fastethernet 0/18

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 S1(config-if)#switchport port-security ?
aging Port-security aging commands
mac-address Secure mac address
maximum Max secure addresses
violation Security violation mode
<cr>
S1(config-if)# switchport port-security

Step 6: Configure port security on an access port.

Configure switch port Fast Ethernet 0/18 to accept only two devices, to learn the MAC addresses
of those devices dynamically, and to block traffic from invalid hosts if a violation occurs.

S1(config-if)#switchport mode access

S1(config-if)#switchport port-security
S1(config-if)#switchport port-security maximum 2
S1(config-if)#switchport port-security mac-address sticky
S1(config-if)#switchport port-security violation protect
S1(config-if)#exit

Step 7: Verify the results.

Show the port security settings.

S1#show port-security

How many secure addresses are allowed on Fast Ethernet 0/18? __________________
What is the security action for this port? ______________________________________

Step 8: Modify the port security settings on a port.

On interface Fast Ethernet 0/18, change the port security maximum MAC address count to 1 and
to shutdown if a violation occurs.

S1(config-if)#switchport port-security maximum 1

S1(config-if)#switchport port-security violation shutdown

Step 9: Verify the results.

Show the port security settings.

S1#show port-security

Have the port security settings changed to reflect the modifications in Step 6? ___________
Ping the VLAN xx address of the switch from PC1 to verify connectivity and to refresh the MAC
address table. You should now see the MAC address for PC1 “stuck” to the running configuration.

Step 10: Introduce a rogue host.

Disconnect PC1 and connect PC2 to port Fast Ethernet 0/18. Ping the VLAN xx address
172.17.xx.11 from the new host.
Record any observations:
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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Step 11: Show port configuration information.
To see the configuration information for just Fast Ethernet port 0/18, issue the following command
in privileged EXEC mode:

S1#show interface fastethernet 0/18

What is the state of this interface?

Fast Ethernet0/18 is ______________ Line protocol is _______________

Step 12: Reactivate the port.

If a security violation occurs and the port is shut down, you can use the no shutdown command to
reactivate it. However, as long as the rogue host is attached to Fast Ethernet 0/18, any traffic
from the host disables the port. Reconnect PC1 to Fast Ethernet 0/18, and enter the following
commands on the switch:

S1# configure terminal

S1(config)#interface fastethernet 0/18
S1(config-if)# no shutdown
S1(config-if)#exit

Note: Some IOS version may require a manual shutdown command before entering the no
shutdown command

IV. Conclusion

*End of Lab Worksheet 3*