CCNA Ch. 1 - Implementing Ethernet Virtual LANs

Question 1

A LAN includes all devices in the same

Answer 1

broadcast domain

Question 2

Five reasons to create smaller broadcast domains

Answer 2

• Reduce CPU overhead by reducing the number of hosts that get each broadcast frame
• Reduce security risks by reducing the number of hosts that see each frame
• Create a more flexible network design by grouping people logically instead of physically
• Reduce the failure domain of many problems, leading to faster troubleshooting times
• Reduce the workload for STP by limiting the VLAN to a single switch

Question 3

Define VLAN tagging

Answer 3

The extra VLAN trunking header includes a VLAN identifier (VLAN ID) field so that the sending switch can associate the frame with a particular VLAN ID, and the recieveing switch can then know in what VLAN each frame belongs.

Question 4

What are the normal and extended VLAN ID ranges?

Answer 4

Cisco switches break the range of VLAN IDs (1-4094) into two ranges, the normal range (1-1005) and the extended range (1006-4094). Only some switches can use extended while all can use the normal range.

Question 5

What is and why us a native VLAN?

Answer 5

By definition, the native VLAN does not require a 802.1Q header. It is assumed that if a switch receives a frame without a trunking header, that the frame belongs to the native VLAN. Both switches must agree on which VLAN is the native VLAN. Native VLANs allow switches that understand trunking to communicate with switches that don’t

Question 6

VTP and its three modes

Answer 6

VLAN Trunking Protocol (VTP)

A proprietary tool on Cisco switches that advertieses each VLAN configured in one switch so that all switches in the campus learn about that VLAN

Each switch can choose one of three VTP modes: server, client, or transparent. With many Cisco IOS version, VTP cannot be completely disabled, so instead a switch disables VTP by setting it to VTP transparent mode

Question 7

DTP

Answer 7

Dynamic Trunking Protocol (DTP) handles negotiations related to trunking

Question 8

Define the four VLAN trunking administrative modes

Answer 8

• access: Always act as an access port
• trunk: Always act as a trunk port
• dynamic desirable: Initiates negotiation messages and responds to negotiation messages to dynamically choose whether to start using trunking
• dynamic auto: Passively waits to recieve trunk negotiation messages, at which point the swithc will respond and negotiate whether to use trunking

Question 9

The two VLANs required for IP phones to work

Answer 9

• Data VLAN: Same idea and configuration as the access VLAN on an access port, but defined as the VLAN on that link for forwarding the traffic for the device connected to the phone on the desk (usually the PC)
• Voice VLAN: The VLAN defined on the link for forwarding the phone’s traffic. Typically tagged with a 802.1Q header

Question 10

Creates the VLAN and puts the CLI into VLAN configuration mode

Answer 10

vlan

Question 11

VLAN subcommand that names the VLAN

Answer 11

name

Question 12

VLAN mode subcommand that enables or disables the VLAN

Answer 12

[no] shutdown

Question 13

Global config command that defines the VTP mode

Answer 13

vtp mode {server | client | transparent | off}

Question 14

Interface subcommand that configures the trunking administrative mode on the interface

Answer 14

switchport mode {access | dynamic auto | dynamic desirable | trunk}

Question 15

Interface subcommand that statically configures the interface into that on VLAN

Answer 15

switchport access vlan

Question 16

Interface subcommand that defines which type of trunking to use

Answer 16

switchport trunk encapsulation {dot1q | isl | negotiate}

Question 17

Interface subcommand that defines the native VLAN for a trunk port

Answer 17

switchport trunk native vlan

Question 18

Interface subcommand that disables the negotiation of VLAN trunking

Answer 18

switchport nonegotiate

Question 19

Interface subcommand that defines the voice VLAN on a port

Answer 19

switchport voice vlan

Question 20

Interface subcommand that defines the list of allowed VLANs

Answer 20

switchport trunk allowed vlan {add | all| except | remove}

Question 21

Lists information about any interface regarding administrative settings and operational use

Answer 21

show interfaces [interface-id] switchport

Question 22

Lists information about all operational trunks (but no other interfaces), including the list of VLANs that can be forwarded over the trunk

Answer 22

show interfaces [interface-id] trunk

Question 23

Displays VLAN information

Answer 23

show vlan [vlan]

Question 24

Lists informtion about the VLAN

Answer 24

show vlan [brief | id | name | summary]

Question 25

Lists VTP configuration and status information

Answer 25

show vtp status