7.2.7 Lab – View Network Device MAC Addresses (Answers)


 Objectives

Configure Devices and Verify Connectivity in Part 1

Part 2: Display, Describe, and Analyze MAC Addresses for Ethernet


Context / Scenario

A Layer 2 MAC address uniquely identifies each device on an Ethernet LAN. The manufacturer assigns and stores this address in the NIC's firmware. This lab will investigate and evaluate the components of a MAC address, as well as how to locate this information on a switch or a PC.

You will connect the equipment in the topology depicted. The switch and PC will be configured to match the addressing table. You will validate your settings by attempting to connect to the network.

After configuring the devices and verifying network connection, you'll use a variety of commands to get information from the devices in order to answer questions about your network equipment.

Cisco Catalyst 2960 switches running Cisco IOS Release 15.2(2) were utilised (lanbasek9 image). Other Cisco switches and Cisco IOS versions are also supported. Depending on the model and Cisco IOS version, the available commands and output may differ from what is shown in the labs.

Nota bene: Ensure that the switches have been wiped and are not configured for a startup. If in doubt, consult your teacher.

Instructor Note: The processes for initialising and reloading devices are detailed in the Instructor Lab Manual.


Ressources Required

1 switch (Cisco 2960 running Cisco IOS 15.2(2) lanbasek9 image or equivalent)

1 personal computer (Windows with a terminal emulation program, such as Tera Term)

The console cable is used to configure the Cisco switch through the console ports' Ethernet cables, as seen in the topology.


Instructions

Configure Devices and Verify Connectivity in Part 1

This section configures the network's structure and fundamental parameters, such as interface IP addresses and device names. The Topology and Addressing Table contains information on the device's name and address.


Step 1: Connect the network in the topology depicted.

a. Assemble the devices and cables depicted in the topology.

b. Ensure that all devices in the topology are powered on.

Step 2: Configure the PC's IPv4 address.

a. Assign PC-A an IPv4 address, a subnet mask, and a default gateway address.

b. Ping the switch address from the command prompt on PC-A.


Were the pings effective? Explain.

No. The switch is currently unconfigured.


Step 3: Configure the switch's basic parameters.

In this step, you'll specify the device's name and IP address, as well as disable the switch's DNS lookup.

a. Log in to the switch's console and choose global configuration mode.

Switch> enable
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#
b. Assign a hostname to the switch based on the Addressing Table.
Switch(config)# hostname S1
c. Disable DNS lookup.
S1(config)# no ip domain-lookup
d. Configure and enable the SVI interface for VLAN 1.
S1(config)# interface vlan 1
S1(config-if)# ip address 192.168.1.2 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# end
*Mar 1 00:07:59.048: %SYS-5-CONFIG_I: Configured from console by console
Verify network connection in Step 4.
From PC-A, ping the switch.

Were the pings effective?
Ping attempts should be successful.

Part 2: Display, Describe, and Analyze MAC Addresses for Ethernet
Each device on an Ethernet LAN is issued a MAC address by the manufacturer and saved in the NIC's firmware. Ethernet MAC addresses have a length of 48 bits. They are represented by six groups of hexadecimal numbers separated by dashes, colons, or periods. The following example illustrates the same MAC address in three distinct notational styles:

00-05-9A-3C-78-00 0005.9A3C.7800 00:05:9A3C.7800 0005.9A3C.7800

MAC addresses may also be referred to as physical addresses, hardware addresses, or Ethernet hardware addresses.

You will issue instructions to view and examine the MAC addresses on a PC and a switch.

Analyze the PC-A NIC's MAC address in Step 1.
Consider an example from a separate PC NIC before analysing the MAC address on PC-A. You may examine the MAC address of your NIC by using the ipconfig /all command. Below is an example of a screen output. When running the ipconfig /all command, take note of the term "physical address" for MAC addresses. When reading the MAC address from left to right, the first six hex digits indicate the device's vendor (maker). These first six hex digits (3 bytes) are also referred to as the unique identification for the organisation (OUI). The IEEE organisation assigns this three-byte code to the vendor.

To locate the manufacturer, search the internet for IEEE OUI standards or browse to http://standards-oui.ieee.org/oui.txt to see the registered OUI vendor codes. The last six numbers are the manufacturer-assigned NIC serial number.

Answer the following questions using the results of the ipconfig /all command.
C:\> ipconfig /all

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) 82577LM Gigabit Network Connection
Physical Address. . . . . . . . . : 5C-26-0A-24-2A-60
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::b875:731b:3c7b:c0b1%10(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.147(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Friday, September 6, 2019 11:08:36 AM
Lease Expires . . . . . . . . . . : Saturday, September 7, 2019 11:08:36 AM
Default Gateway . . . . . . . . . : 192.168.1.1
<output omitted?
What is the OUI component of this device's MAC address?
5C-26-0A

What is the serial number component of this device's MAC address?

24-2A-60

Determine the vendor who built this NIC using the example above.

b. From the command prompt on PC-A, type ipconfig /all and note the OUI component of the MAC address for PC-NIC. A's

The answers will vary according on the manufacturer.

Determine the serial number component of the MAC address for PC-NIC. A's

The responses will vary according on the manufacturer serial number code.

Identify the firm that produced the PC-NIC. A's

The answers will differ according on the manufacturer's OUI.

Step 2: Analyze the S1 F0/6 interface's MAC address.
You may show MAC addresses on the switch through a number of instructions.
a. Log into S1 through the console and use the show interfaces vlan 1 command to get the MAC address. Below is an example. Answer the questions using the output given by your switch.
S1# show interfaces vlan 1
Vlan1 is up, line protocol is up
Hardware is EtherSVI, address is 001b.0c6d.8f40 (bia 001b.0c6d.8f40)
Internet address is 192.168.1.2/24
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not supported
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 00:14:51, 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, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
34 packets output, 11119 bytes, 0 underruns
0 output errors, 2 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
Which MAC address is assigned to VLAN 1 on S1?
The student's answers will differ depending on the switch he or she is using. Using the results from the previous section, the answer is 001b.0c6d.8f40.

What is VLAN 1's MAC serial number?

The student's answers will differ depending on the switch he or she is using. Using the result from the previous section, the solution is 6d-8f-40.

What is VLAN 1's OUI?

The student's answers will differ depending on the switch he or she is using. Using the result from the previous section, the solution is 00-1b-0c.

What is the vendor's name based on this OUI?

Cisco Networking Systems

What does the abbreviation bia mean?

Address has been obliterated.

Why is the same MAC address shown twice in the output?

A software command may be used to modify the MAC address. The original address (bia) will remain. It is shown in parentheses.
b. The show arp command is another method to see the switch's MAC address. The show arp command displays information about the MAC address. This command converts the Layer 2 address to its Layer 3 equivalent. Below is an example. Answer the questions using the output given by your switch.
S1# show arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 192.168.1.2 - 001b.0c6d.8f40 ARPA Vlan1
Internet 192.168.1.3 0 5c26.0a24.2a60 ARPA Vlan1

On S1, which Layer 2 addresses are displayed?
MAC addresses for S1 VLAN 1 and PC-A. If the student additionally keeps track of the MAC addresses, their responses will differ.

On S1, which Layer 3 addresses are displayed?

IP addresses for S1 and PC-A

Step 3: Display the switch's MAC addresses.
On S1, execute the display mac address-table command. Below is an example. Answer the questions using the output given by your switch.
Note to the instructor: The display mac address-table command may differ depending on the model switch being used. For instance, on certain switches, the syntax is display mac-address-table.
S1# show mac address-table
Mac Address Table
-------------------------------------------

Vlan Mac Address Type Ports
---- ----------- -------- -----
All 0100.0ccc.cccc STATIC CPU
All 0100.0ccc.cccd STATIC CPU
All 0180.c200.0000 STATIC CPU
All 0180.c200.0001 STATIC CPU
All 0180.c200.0002 STATIC CPU
All 0180.c200.0003 STATIC CPU
All 0180.c200.0004 STATIC CPU
All 0180.c200.0005 STATIC CPU
All 0180.c200.0006 STATIC CPU
All 0180.c200.0007 STATIC CPU
All 0180.c200.0008 STATIC CPU
All 0180.c200.0009 STATIC CPU
All 0180.c200.000a STATIC CPU
All 0180.c200.000b STATIC CPU
All 0180.c200.000c STATIC CPU
All 0180.c200.000d STATIC CPU
All 0180.c200.000e STATIC CPU
All 0180.c200.000f STATIC CPU
All 0180.c200.0010 STATIC CPU
All ffff.ffff.ffff STATIC CPU
1 5c26.0a24.2a60 DYNAMIC Fa0/6
Total Mac Addresses for this criterion: 21
Was the switch displaying PC-MAC A's address? If you responded yes, which port did it originate from?
Yes. The port number should be F0/6. The MAC address will provide a variety of responses. The MAC address in the above example would be 5c26.0a24.2a60.

1. Is it possible to conduct broadcasts at the Layer 2 level? If such is the case, what would be the MAC address?
Layer 2 transmissions are possible. ARP will search for MAC address information through broadcasts. The broadcast address is FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.FF.

2. Why would you need to know a device's MAC address?
There could be numerous reasons. In a vast network, it may be simpler to determine a device's location and identity using its MAC address rather than its IP address. The MAC OUI displays the manufacturer, which might assist in narrowing the search. Layer 2 security measures are possible, and hence knowledge of allowed MAC addresses is required.

Configuration of the Device

S1 switch
S1# show run
Building configuration...

Current configuration : 1335 bytes
!
version 15.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname S1
!
boot-start-marker
boot-end-marker
!
no aaa new-model
system mtu routing 1500
!
no ip domain-lookup
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
ip address 192.168.1.2 255.255.255.0
!
ip http server
ip http secure-server
logging esm config
!
line con 0
line vty 5 15
!
end

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