Week10-Lab-build a network with switch and observe MAC Addresses and ARP PDF

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Week 2 Lab – Observing MAC Addresses and ARP Topology

Addressing Table Device

Interface

IP Address

Subnet Mask

S1

VLAN1

192.168.1.11

255.255.255.0

N/A

S2

VLAN1

192.168.1.12

255.255.255.0

N/A

PC-A

NIC

192.168.1.3

255.255.255.0

192.168.1.1

PC-B

NIC

192.168.1.2

255.255.255.0

192.168.1.1

Objectives Part 1: Get Familiar with Cisco Packet Tracer Part 2: Set Up the Topology and Initialize Devices Part 3: Configure Devices and Verify Connectivity Part 4: Display, Describe, and Analyze Ethernet MAC Addresses Part 5: Use the IOS Show ARP Command

Required Resources ●

Cisco netcad account

●

Cisco Packet Tracer 7.3.0

Part 1: Step 1:

Default Gateway

Get familiar with Cisco Packet Tracer Register CISCO account

a. Go to h  ttps://www.netacad.com/ and create an account. b. Download CISCO Packet Tracer 7.3.0 fitting your system https://www.netacad.com/portal/resources/packet-tracer.

c. Install the Packet Tracer, Open the Packet Tracer and Log in with your account. You will see the Cisco Packet Tracer as below.

A tutorial of Packet Tracer can be found here http://static-pt-assets.s3.amazonaws.com/tutorials72.htm

Part 1: Set Up the Topology and Initialize Devices In Part 1, you will set up the network topology, clear any configurations, if necessary, and configure basic settings, such as the interface IP addresses on the router and PCs.

Step 1:

Cable the network as shown in the Topology.

a. Attach the devices shown in the Topology and cable as necessary. b. Power on all the devices in the topology. Build the network as shown in the Topology using Packet Tracer. From the bottom-left Device Box, choose “N  etwork Devices” -> “Switch-PT” -> “2960” and drag the switch to your canvas as the S1 and S2.

And from “End Devices” choose “E  nd Devices” -> “PC”, as your PC-A and PC-B:

From the “Connections”, select the corresponding “Copper S  traight-Through” and “Copper Cross-Over” cables to connect the swtiches and PCs, and the two switches using the corresponding ports as shown in the Toplogy. Select the cable first, then click the devices to be connected and select given interface.

PS. Select “Options” -> “Preferences” to u  ncheck “Show Device Model Labels” and check “Show Device Name Labels” and “Always Show Port Label in Logical Workspace”.

Step 2:

Establish console connection and initialize and reload the switches.

Before starting a hands-on lab that makes use of either a Cisco router or switch, you should ALWAYS ensure that the devices in use have been erased and have no startup configurations present. Otherwise, the results of your lab may be unpredictable. Make sure that the switches have been erased and have no startup configurations. If you are unsure, refer to Appendix A for detailed steps for initializing switches. If the switches have been password protected, refer to Appendix B  for password recovery.

Part 2: Configure Devices and Verify Connectivity In Part 2, you will configure basic settings, such as the interface IP addresses and device access. For device names and address information, refer to the Topology and Addressing Table.

Step 1:

Configure basic settings for the switch S1.

In this step, you will configure the device name and the IP address, and disable DNS lookup on the switch S1.

a. Console into the switch and enter global configuration mode. PS. How to console into the switch: Connect to the switch S1’s Console port using a serial console cable from PC-A communication port, and open PuTTy on the desktop of PC-A (connect via Serial).

In Packet Tracer, click the switch and from the open dialog, click the “C  LI” tap on the top to enter the CLI of the switch. Hit the Enter key on your keyboard when the dialog is active and then you will see the system prompt “Switch>”. The console connection is ready for you to proceed with the rest switch configuration. PS, click the “Config” tab and you may change the d  isplay name of the devices.

Switch> enable Switch# configure terminal Enter configuration commands, one per line. Switch(config)#

End with CNTL/Z.

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 192.168.1.11 255.255.255.0 S1(config-if)# no shutdown S1(config-if)# end *Mar

Step 2:

1 00:07:59.048: %SYS-5-CONFIG_I: Configured from console by console

Configure basic settings for the switch S2.

In this step, you will configure the device name and the IP address, and disable DNS lookup on the switch S2.

a. Console into the switch and enter global configuration mode.

PS. How to console into the switch: Connect to the switch S2’s Console port using a serial console cable from PC-B communication port, and open PuTTy on the desktop of PC-B (connect via Serial).

Switch> enable Switch# configure terminal Enter configuration commands, one per line. Switch(config)#

End with CNTL/Z.

b. Assign a hostname to the switch based on the Addressing Table. Switch(config)# hostname S2

c. Disable DNS lookup. S2(config)# no ip domain-lookup

d. Configure and enable the SVI interface for VLAN 1. S2(config)# interface vlan 1 S2(config-if)# ip address 192.168.1.12 255.255.255.0 S2(config-if)# no shutdown S2(config-if)# end *Mar

Step 3:

1 00:07:59.048: %SYS-5-CONFIG_I: Configured from console by console

Configure the IPv4 addresses for the PCs.

a. Configure the IPv4 address, subnet mask, and default gateway address for PC-A and PC-B according to the Addressing Table. In Packet Tracer, click PC-A (do the same for PC-B after). On the open dialog, click the “D  esktop” tap and then “IP Configuration” box to configure the PC’s IP address information according to the Addressing Table:

b. Open the Window’s command prompt (cmd.exe) and type ipconfig /all to verify the IP configuration of the hosts. PS. In Packet Tracer, click PC-A (do the same for PC-B after). On the open dialog, click the “Desktop” tap and then “Command Prompt” box to open the Window’s Command Prompt (cmd.exe) and run the Windows cmd commands.

Step 4:

Verify network connectivity.

a. Ping the switches VLAN1 from each of PC-A and PC-B’s command prompt. Were the pings successful? Yes  they were successful. If not, check your cabling and configuration and ask your instructor for help.

Part 3: Display, Describe, and Analyze Ethernet MAC Addresses Every device on an Ethernet LAN has a MAC address that is assigned by the manufacturer and stored in the firmware of the NIC. Ethernet MAC addresses are 48-bit long. They are displayed using six sets of hexadecimal digits that are usually separated by dashes, colons, or periods. The following example shows the same MAC address using the three different notation methods: 00-05-9A-3C-78-00

00:05:9A:3C:78:00

0005.9A3C.7800

Note: MAC addresses are also called physical addresses, hardware addresses, or Ethernet hardware addresses. You will issue commands to display the MAC addresses on a PC and a switch, and analyze their properties.

Step 1:

Analyze the MAC address for PC-A’s and PC-B’s NICs.

Before you analyze the MAC address on PC-A, look at an example from a different PC NIC. You can issue the ipconfig /all command to view the MAC address of your NIC. An example screen output is shown below. 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. . . . . . . . . . . : 192.168.1.2(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



When using the ipconfig /all command, notice that MAC addresses are referred to as physical addresses. Reading the MAC address from left to right, the first six hex digits refer to the vendor (manufacturer) of this device. These first six hex digits (3 bytes) are also known as the organizationally unique identifier (OUI). This 3-byte code is assigned to the vendor by the IEEE organization. To find the manufacturer, use the keywords IEEE OUI standards to find an OUI lookup tool on the internet or navigate to h  ttp://standards-oui.ieee.org/oui.txt to find the registered OUI vendor codes. The last six digits are the NIC serial number assigned by the manufacturer.

a. Open a command prompt on PC-A and PC-B and type ipconfig /all. What are the LAN connection adapter’s physical addresses? PC-A MAC Address: 0001.43DC.DDB3  What is the OUI portion of the MAC address for PC-A?. 0001.43 What is the serial number portion of the MAC address for PC-A? DC.DDB3 PC-B MAC Address: 0006.2A33.4B24  What is the OUI portion of the MAC address for PC-B? 0006.2A. What is the serial number portion of the MAC address for PC-B? 33.4B24. Find the name of the vendor that manufactured these NICs. Cisco Systems Inc.

Step 2:

Examine the MAC addresses for the switches S1 and S2.

You can use a variety of commands to display MAC addresses on the switch.

a. Console into the switches and use the show interfaces command for vlan 1 and port Fa0/6 or Fa0/18 to display MAC address information. A sample is shown below. Use the output generated by your switch to answer the questions. 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 192.168.1.11/24 MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set

S2# show interface f0/18 FastEthernet0/18 is up, line protocol is up (connected) Hardware is Fast Ethernet, address is 0025.83e6.9081 (bia 0025.83e6.9081) MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,

On the second line of command output, what are the hardware addresses (or burned-in address [bia])? S1 vlan1 MAC Address: 000c.8506.5bd0  S2 Fast Ethernet 0/18 MAC Address: 0003.e41d.3c12

b. Another way to display the MAC address on the switch is to use the show arp command. Use the show arp command to display MAC address information. This command maps the Layer 2 address to its corresponding Layer 3 address. Use output generated by your switch to answer the questions. What Layer 2 addresses are displayed on S1? 000C.8506.5BD0, 0001.4314.D3E4 What Layer 3 addresses are displayed on S1? 192.168.1.12 (S4), 192.168.1.11 (S3)

Step 3:

Display the switch MAC address table.

Issue the show mac address-table command on S1. Use output generated by your switch to answer the questions. Instructor Note: The show mac address-table command can vary based on the model switch you are using. For example, the syntax on some switches is show mac-address-table. S1# show  mac address-table

Even though there has been no network communication initiated across the network (i.e., no use of ping), it is possible that the switch has learned MAC addresses from its connection to the PCs and the other switch. Are there any MAC addresses recorded in the MAC address table? Yes there is one MAC address. What MAC addresses are recorded in the table? To which switch ports are they mapped and to which devices do they belong? Ignore MAC addresses that are mapped to the CPU. The MAC address is 0003.e41d.3c01 is mapped to port Fa0/1 which belongs to PC2 If you had not previously recorded MAC addresses of network devices in Step 1, how could you tell which devices the MAC addresses belong to, using only the output from the show mac address-table command? Does it work in all scenarios? You can use the ipconfig /all command on the PC’s command prompt and viewing their physical addresses and compare to the address table command.

Step 4:

Clear the S2 MAC address table and display the MAC address table again.

a. In privileged EXEC mode, type the clear mac address-table dynamic command and press Enter. S2# clear mac address-table dynamic

b. Quickly type the show mac address-table command again. Does the MAC address table have any addresses in it for VLAN 1? Are there other MAC addresses listed? Yes there is one. Wait 10 seconds, type the show mac address-table command, and press Enter. Are there new addresses in the MAC address table? There are no new addresses. From PC-B, ping the devices on the network and observe the switch MAC address table.

c. From PC-B, open a command prompt and type arp -a. Not including multicast or broadcast addresses, how many device IP-to-MAC address pairs have been learned by ARP? There is one displayed.

d. From the PC-B command prompt, ping PC-A, S1, and S2. Did all devices have successful replies? If not, check your cabling and IP configurations. Yes all devices had successful replies.

e. From a console connection to S2, enter the show mac address-table command. Has the switch added additional MAC addresses to the MAC address table? If so, which addresses and devices? Yes there are 3 new ones.

Internet Address Physical Address Type 192.168.1.3 0001.43dc.ddb3 dynamic 192.168.1.11 000c.8506.5bd0 dynamic 192.168.1.12 0001.4314.d3e4 dynamic

From PC-B, open a command prompt and retype arp -a. Does the PC-B ARP cache have additional entries for all network devices that were sent pings? If so, which do they devices do they correspond with? Yes, there are 2 new entries shown that correspond with devices PC-A and S1.

Reflection 1. Can you have broadcasts at the Layer 2 level? If so, what would the MAC address be? Yes broadcasts can be present at layer 2 level. ARP will use broadcasts for MAC address which will be FF.FF.FF.FF.FF.FF.

2. Why would you need to know the MAC address of a device? MAC address provides information for identification purposes. It can be used to identify a device as it is easier than using an IP address.

3. On Ethernet networks, data is delivered to devices by their MAC addresses. For this to happen, switches and PCs dynamically build ARP caches and MAC address tables. With only a few computers on the network this process seems fairly easy. What might be some of the challenges on larger networks?

On larger networks, presence of more devices can slow down the ARP cache. Consequently, we get more discrepancies, errors and inaccuracies on networks which are larger.

Part 4: Use the IOS show arp Command The Cisco IOS on routers and switches can also display the ARP cache on routers and switches with the show arp or show  ip arp command.

Step 1:

Display ARP entries on switch S1. S1# show ip arp

Step 2:

Protocol Internet

Address 192.168.1.2

Internet Internet S1#

192.168.1.3 192.168.1.11

Age (min) 8 8 -

Hardware Addr 0050.56be.f6db

Type ARPA

Interface Vlan1

0050.56be.768c 0cd9.96e8.8a40

ARPA ARPA

Vlan1 Vlan1

Add ARP entries on switch S1.

By pinging other devices, ARP entries can also be added to the ARP table of the switch.

a. From switch S1, ping switch S2. S1# ping 192.168.1.12 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.12, timeout is 2 seconds: .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 1/2/8 ms

b. Verify that the ARP entry for switch S2 has been added to ARP table of S1. S1# show ip arp Protocol Internet

Address 192.168.1.2

Internet Internet Internet

192.168.1.3 192.168.1.11 192.168.1.12

S1#

Age (min) 11 11 2

Hardware Addr 0050.56be.f6db

Type ARPA

Interface Vlan1

0050.56be.768c 0cd9.96e8.8a40 0cd9.96d2.4040

ARPA ARPA ARPA

Vlan1 Vlan1 Vlan1...