CCNA RSE Lab: 6.2.2.5 Configuring VLANs and Trunking

CCNA RSE Lab: 6.2.2.5 Configuring VLANs and Trunking

Topology

ccna-rse-lab-configuring-vlans-trunking

Addressing Table

Device Interface IP Address Subnet Mask Default Gateway
S1 VLAN 1 192.168.1.11 255.255.255.0 N/A
S2 VLAN 1 192.168.1.12 255.255.255.0 N/A
PC-A NIC 192.168.1 0.3 255.255.255.0 192.168.1 0.1
PC-B NIC 192.168.10.4 255.255.255.0 192.168.0.1
PC-C NIC 192.168.20.3 255.255.255.0 192.168.20.1

Objectives
Part 1: Build the Network and Configure Basic Device Settings
Part 2: Create VLANs and Assign Switch Ports
Part 3: Maintain VLAN Port Assignments and the VLAN Database
Part 4: Configure an 802.1Q Trunk between the Switches
Part 5: Delete the VLAN Database

Background / Scenario
Modern switches use virtual local-area networks (VLANs) to improve network performance by separating large Layer 2 broadcast domains into smaller ones. VLANs can also be used as a security measure by controlling which hosts can communicate. In general, VLANs make it easier to design a network to support the goals of an organization.

VLAN trunks are used to span VLANs across multiple devices. Trunks allow the traffic from multiple VLANS to travel over a single link, while keeping the VLAN identification and segmentation intact. In this lab, you will create VLANs on both switches in the topology, assign VLANs to switch access ports, verify that VLANs are working as expected, and then create a VLAN trunk between the two switches to allow hosts in the same VLAN to communicate through the trunk, regardless of which switch the host is actually attached to.

Note: The switches used are Cisco Catalyst 2960s with Cisco IOS Release 1 5.0(2) (lanbasek9 image). Other switches and Cisco IOS versions can be used. Depending on the model and Cisco IOS version, the commands available and output produced might vary from what is shown in the labs.

Note: Ensure that the switches have been erased and have no startup configurations. If you are unsure contact your instructor.

Instructor Note: Refer to the Instructor Lab Manual for the procedures to initialize and reload devices.

Required Resources

  • 2 Switches (Cisco 2960 with Cisco IOS Release 15.0(2) lanbasek9 image or comparable)
  • 3 PCs (Windows 7, Vista, or XP with terminal emulation program, such as Tera Term)
  • Console cables to configure the Cisco IOS devices via the console ports
  • Ethernet cables as shown in the topology
Part 1: Build the Network and Configure Basic Device Settings

In Part 1, you will set up the network topology and configure basic settings on the PC hosts and switches.

Step 1: Cable the network as shown in the topology.
Attach the devices as shown in the topology diagram, and cable as necessary.
Step 2: Initialize and reload the switches as necessary.

Step 3: Configure basic settings for each switch.
a. Console into the switch and enter global configuration mode.
b. Copy the following basic configuration and paste it to the running-configuration on the switch.

c. Configure the host name as shown in the topology.
d. Configure the IP address listed in the Addressing Table for VLAN 1 on the switch.
e. Administratively deactivate all unused ports on the switch.
f. Copy the running configuration to the startup configuration.

Step 4: Configure PC hosts.
Refer to the Addressing Table for PC host address information.

Step 5: Test connectivity.
Verify that the PC hosts can ping one another.

Note: It may be necessary to disable the PCs firewall to ping between PCs.
Can PC-A ping PC-B? _________ Yes
Can PC-A ping PC-C? _________ No
Can PC-A ping S1? _________ No
Can PC-B ping PC-C? _________ No
Can PC-B ping S2? _________ No
Can PC-C ping S2? _________ No
Can S1 ping S2? _________ Yes

If you answered no to any of the above questions, why were the pings unsuccessful?
Pings were unsuccessful when trying to ping a device on a different subnet. For those pings to be successful, a default gateway must exist to route traffic from one subnet to another.

Part 2: Create VLANs and Assign Switch Ports

In Part 2, you will create student, faculty, and management VLANs on both switches. You will then assign the
VLANs to the appropriate interface. The show vlan command is used to verify your configuration settings.

Step 1: Create VLANs on the switches.
a. Create the VLANs on S1 .

b. Create the same VLANs on S2.
c. Issue the show vlan command to view the list of VLANs on S1 .

S1# show vlan
ccna-rse-lab-configuring-vlans-trunking-1

What is the default VLAN? ___________ VLAN 1

What ports are assigned to the default VLAN?
All switch ports are assigned to VLAN 1 by default.

Step 2: Assign VLANs to the correct switch interfaces.
a. Assign VLANs to the interfaces on S1.

b. Issue the show vlan brief command and verify that the VLANs are assigned to the correct interfaces.
ccna-rse-lab-configuring-vlans-trunking-2

c. Issue the show ip interface brief command.

What is the status of VLAN 99? Why?
The status of VLAN 99 is up/down, because it has not been assigned to an active port yet.

d. Use the Topology to assign VLANs to the appropriate ports on S2.
e. Remove the IP address for VLAN 1 on S2.
f. Configure an IP address for VLAN 99 on S2 according to the Addressing Table.
g. Use the show vlan brief command to verify that the VLANs are assigned to the correct interfaces.

ccna-rse-lab-configuring-vlans-trunking-3

Is PC-A able to ping PC-B? Why?
No. Interface F0/1 is not assigned to VLAN 10, so VLAN 10 traffic will not be sent over it.

Is S1 able to ping S2? Why?
No. The IP addresses for the switches now reside in VLAN 99. VLAN 99 traffic will not be sent over interface F0/1 .

Part 3: Maintain VLAN Port Assignments and the VLAN Database

In Part 3, you will change VLAN assignments to ports and remove VLANs from the VLAN database.

Step 1: Assign a VLAN to multiple interfaces.
a. On S1, assign interfaces F0/11 – 24 to VLAN 10.

b. Issue the show vlan brief command to verify VLAN assignments
ccna-rse-lab-configuring-vlans-trunking-4
c. Reassign F0/11 and F0/21 to VLAN 20.

d. Verify that VLAN assignments are correct.
ccna-rse-lab-configuring-vlans-trunking-5
ccna-rse-lab-configuring-vlans-trunking-5-1
tep 2: Remove a VLAN assignment from an interface.
a. Use the no switchport access vlan command to remove the VLAN 1 0 assignment to F0/24.

b. Verify that the VLAN change was made.
Which VLAN is F0/24 now associated with?
VLAN 1, the default VLAN.
ccna-rse-lab-configuring-vlans-trunking-6
Step 3: Remove a VLAN ID from the VLAN database.
a. Add VLAN 30 to interface F0/24 without issuing the VLAN command.

Note: Current switch technology no longer requires that the vlan command be issued to add a VLAN to the database. By assigning an unknown VLAN to a port, the VLAN adds to the VLAN database.

b. Verify that the new VLAN is displayed in the VLAN table.
ccna-rse-lab-configuring-vlans-trunking-7
ccna-rse-lab-configuring-vlans-trunking-7-1

What is the default name of VLAN 30?
VLAN0030

c. Use the no vlan 30 command to remove VLAN 30 from the VLAN database.

d. Issue the show vlan brief command. F0/24 was assigned to VLAN 30.
After deleting VLAN 30, what VLAN is port F0/24 assigned to? What happens to the traffic destined to the host attached to F0/24?

Port F0/24 is not assigned to any VLAN. This port will not transfer any traffic.

ccna-rse-lab-configuring-vlans-trunking-8

e. Issue the no switchport access vlan command on interface F0/24.

f. Issue the show vlan brief command to determine the VLAN assignment for F0/24. To which VLAN is F0/24 assigned?
VLAN 1

ccna-rse-lab-configuring-vlans-trunking-9
Note: Before removing a VLAN from the database, it is recommended that you reassign all the ports assigned to that VLAN.

Why should you reassign a port to another VLAN before removing the VLAN from the VLAN database?
The interfaces assigned to a VLAN that is the removed from the VLAN database are unavailable for use until they are reassigned to another VLAN. This can be a tricky thing to troubleshoot as trunked interfaces do not show up in the port list as well (Part 4 contains more information about trunked interfaces).

Part 4: Configure an 802.1Q Trunk Between the Switches
In Part 4, you will configure interface F0/1 to use the Dynamic Trunking Protocol (DTP) to allow it to negotiate the trunk mode. After this has been accomplished and verified, you will disable DTP on interface F0/1 and manually configure it as a trunk.

Step 1: Use DTP to initiate trunking on F0/1 .
The default DTP mode of a 2960 switch port is dynamic auto. This allows the interface to convert the link to a trunk if the neighboring interface is set to trunk or dynamic desirable mode.

a. Set F0/1 on S1 to negotiate trunk mode.

ccna-rse-lab-configuring-vlans-trunking-10
b. Issue the show vlan brief command on S1 and S2. Interface F0/1 is no longer assigned to VLAN 1. Trunked interfaces are not listed in the VLAN table.

ccna-rse-lab-configuring-vlans-trunking-11

c. Issue the show interfaces trunk command to view trunked interfaces. Notice that the mode on S1 is set to desirable, and the mode on S2 is set to auto.

ccna-rse-lab-configuring-vlans-trunking-12

Note: By default, all VLANs are allowed on a trunk. The switchport trunk command allows you to control what VLANs have access to the trunk. For this lab, keep the default settings which allows all VLANs to traverse F0/1 .

d. Verify that VLAN traffic is traveling over trunk interface F0/1.
Can S1 ping S2? ___________ Yes
Can PC-A ping PC-B? ___________ Yes
Can PC-A ping PC-C? ___________ No
Can PC-B ping PC-C? ___________ No
Can PC-A ping S1? ___________ No
Can PC-B ping S2? ___________ No
Can PC-C ping S2? ___________ No

If you answered no to any of the above questions, explain below.
PC-C cannot ping PC-A or PC-B because PC-C is in a different VLAN. The switches are in different VLANs than the PCs; therefore, the pings were unsuccessful.

Step 2: Manually configure trunk interface F0/1.
The switchport mode trunk command is used to manually configure a port as a trunk. This command should be issued on both ends of the link.

a. Change the switchport mode on interface F0/1 to force trunking. Make sure to do this on both switches.

b. Issue the show interfaces trunk command to view the trunk mode. Notice that the mode changed from desirable to on.

ccna-rse-lab-configuring-vlans-trunking-13

Why might you want to manually configure an interface to trunk mode instead of using DTP?
Not all equipment uses DTP. Using the switchport mode trunk command ensures that the port will become a trunk no matter what type of equipment is connected to the other end of the link.

Part 5: Delete the VLAN Database

In Part 5, you will delete the VLAN Database from the switch. It is necessary to do this when initializing a switch back to its default settings.

Step 1: Determine if the VLAN database exists.
Issue the show flash command to determine if a vlan.dat file exists in flash.

ccna-rse-lab-configuring-vlans-trunking-14
Note: If there is a vlan.dat file located in flash, then the VLAN database does not contain its default settings.

Step 2: Delete the VLAN database.
a. Issue the delete vlan.dat command to delete the vlan.dat file from flash and reset the VLAN database back to its default settings. You will be prompted twice to confirm that you want to delete the vlan.dat file.

b. Issue the show flash command to verify that the vlan.dat file has been deleted.

To initialize a switch back to its default settings, what other commands are needed?

To get a switch back to its default settings, the erase startup-config and reload commands need to be issued after the delete vlan.dat command.

Reflection
1. What is needed to allow hosts on VLAN 10 to communicate to hosts on VLAN 20?
Answers will vary, but Layer 3 routing is needed to route traffic between VLANs.

2. What are some primary benefits that an organization can receive through effective use of VLANs?
Answers will vary, but VLAN benefits include: better security, cost savings (efficient use of bandwidth and uplinks), higher performance (smaller broadcast domains), broadcast storm mitigation, improved IT staff efficiency, simpler project and application management.

Device Configs – Final
Switch S1

Switch S2

More Resources

About the author

Prasanna

Leave a Comment