Chapter 8: Implementing Ethernet Virtual LANs

Question 1

What does a VLAN allow?

Answer 1

Multiple broadcast domains on one device

Question 2

Which hosts receive frames sent within a VLAN?

Answer 2

Only other hosts within the same VLAN

Question 3

List 3 advantages of VLANs, along with the reasoning

Answer 3

Reduce CPU usage - Reducing number of devices receiving frames
Reduce security risks - Reducing hosts which receive copies of frames
Improve security - Apply security policies to different VLANs
Reduce STP workload
Faster problem solving - Issues limited by devices on broadcast domain
Group users by department, not physical location

Question 4

What does VLAN tagging do?

Answer 4

Adds extra header to the frame

Question 5

What process inserts a VLAN header to a frame?

Answer 5

VLAN tagging

Question 6

What is a VLAN trunk?

Answer 6

One link containing multiple VLANs

Question 7

Name IEEE protocol name for a VLAN

Answer 7

802.1Q

Question 8

What is different about frames within a networks default VLAN?

Answer 8

No VLAN tag is inserted into the header

Question 9

What is the name for multiple VLANs running over 1 link?

Answer 9

VLAN trunking

Question 10

What command creates a VLAN? What configuration mode is required?

Answer 10

VLAN <vlan-ID>
Global configuration</vlan-ID>

Question 11

What commands assign a VLAN to an access interface?

Answer 11

Interface <interface-ID> - on which the VLAN is required
Switchport access vlan <vlan-ID></vlan-ID></interface-ID>

Question 12

What command shows the VLAN settings of the router?

Answer 12

Show vlan brief

Question 13

What would the following achieve?

interface range Fastethernet 0/15-16
switchport access vlan 3

Answer 13

Assign VLAN 3 to interfaces Fa0/15 and 16

Question 14

What command ensures an interface only acts as an access port, not a trunk?

Answer 14

Switchport mode access

Question 15

What is VTP?

Answer 15

VLAN Trunking Protocol. Cisco protocol which advertises a each VLAN so all switches on a site learn about it

Question 16

What command ensures an interface acts as a trunk port?

Answer 16

Switchport mode trunk

Question 17

What switchport mode do switches default to? What does this mean?

Answer 17

Auto. Neither port will initiate a trunk negotiation process

Question 18

List the command which tells a switch to initiate trunk negotiation

Answer 18

Swtichport mode dynamic desirable

Question 19

With all interfaces set as switchport mode dynamic auto, what would show in the show interfaces trunk output? Why?

Answer 19

Nothing. No trunks are configured, as no switches start the negotiation process

Question 20

What does command switchport mode access set?

Answer 20

Tells an interface to only act as an access interface

Question 21

What does switchport mode dynamic desirable set?

Answer 21

Both ports to negotiate switchport mode, and to initiate the negotiation

Question 22

In what situation can a port act as both an access and a trunk?

Answer 22

IP Telephone

Question 23

What must be enabled for a voice access port?

Answer 23

CDP

Question 24

List a minimum of 2 steps an engineer can take to troubleshoot VLAN issues

Answer 24

Check they are defined and active
Check the VLAN is allowed on both ends of each trunk
Check for incorrect trunk configuration
Check native VLAN on each end of trunk to ensure match

Question 25

What trunk status would an interface with both native and voice VLANs enabled show as?

Answer 25

Not trunking

Question 26

What occurs when one switch is trunking, however the other end is not?

Answer 26

Frames are discarded, as they have a VLAN tag in the header