VLANs

Question 1

What OSI Layer do VLANs live at?

Answer 1

Layer 2

Question 2

True or False - Switches do not forward broadcast traffic by default

Answer 2

False. They do forward broadcast traffic by default

Question 3

True or False - Switches forward broadcast traffic everywhere, including between IP Subnets

Answer 3

True

Question 4

What kind of traffic were VLANs designed to segment?

Answer 4

Broadcast Traffic

Question 5

What does broadcast traffic on a switch bypass?

Answer 5

It bypasses the router and/or the firewall because it’s a Layer 2 broadcast

Question 6

VLANS segment the LAN into what?

Answer 6

Separate Broadcast Domains

Question 7

If you have VLANs set up on a switch, the switch will only allow traffic within the same what?

Answer 7

VLAN

Question 8

How would you create a VLAN on a switch?

Answer 8

vlan {vlan #id}
vlan {name}

Question 9

How would you put an interface in a specific VLAN?

Answer 9

int {int}
switchport mode access
switchport acc vlan {vlan-id}

Question 10

How would you configure a range of interfaces from fa0/1 to fa0/5 to go in a VLAN?

Answer 10

int range fa0/1 - 5
sw mode access
sw acc vlan {vlan #id}

Question 11

What is the command to verify which ports are in specific VLANs?

Answer 11

show vlan brief

Question 12

What is the command to view specific information about a switchport?

Answer 12

show int {int} switchport

Question 13

If you’re sending unicast traffic to a different subnet with both devices in VLAN 1 will the traffic make it there without a router?

Answer 13

No, unicast traffic between subnets still need a router to get to where it’s going

Question 14

Scenario: You have 3 computers.

PC1: 10.10.10.5/24
PC2: 10.10.10.6/24
PC3: 10.10.20.2/24
All 3 are in VLAN 1

If PC1 sends a ping to 10.10.10.255 will PC3 receive that broadcast traffic as well?

Answer 14

Yes, broadcast traffic, regardless of what subnet the device is in, will get forwarded out ALL ports on the switch.

Question 15

Do switches send traffic between multiple VLANs?

Answer 15

No, routers do this

Question 16

What encapsulation mode is a VLAN Trunk configured in?

Answer 16

Dot1Q

Question 17

Why would you want to have trunk ports between switches?

Answer 17

So that your devices can talk to other devices in their same VLAN on other switches.

Question 18

What happens to the Layer 2 header when it forwards traffic to another switch for the same VLAN?

Answer 18

It tags the Layer 2 Dot1Q header with the correct VLAN

Question 19

When a switch receives a packet with a Layer 2 header Dot1Q VLAN tag for VLAN 299. What ports will it send that traffic out of?

Answer 19

Only ports configured in VLAN 299

Question 20

What happens when a switch forwards traffic tagged with a Dot1Q VLAN out to an access port?

Answer 20

It strips the Layer 2 Dot1Q tag. The end device isn’t VLAN aware so it wouldn’t know what do with it

Question 21

Scenario: If you have a server with multiple VMs running in multiple different VLANs, what should you make sure of?

Answer 21

You need to have the link between the switch and the server trunked

Question 22

True or False - For a phone that is daisychained, you only need to have the voice vlan command configured

Answer 22

False. You need to the port configured in access mode and also the access vlan designation as well

Question 23

How would you configure a trunkport?

Answer 23

int {int}
description {description of trunk port}
switchport trunk encapsulation dot1q (modern switches don’t require this command)
switchport mode trunk

Question 24

Do you need to configure both sides of the link to be a trunk?

Answer 24

Yes

Question 25

What is the default native VLAN?

Answer 25

1

Question 26

Do Native VLANs have to match on both sides of a trunk to come up?

Answer 26

Yes

Question 27

What is a Native VLAN used for?

Answer 27

To assign any traffic which is untagged on a trunk port to the native VLAN

Question 28

What is a full configuration for a Trunk Port to SW2 with a Native VLAN of 100 on int gi1/0/1

Answer 28

vlan 100 name Native VLAN int {int} description Trunk to SW2 switchport trunk encapsulation dot1q switchport mode trunk switchport trunk native vlan 100

Question 29

How would you LIMIT allowed VLANs on a switch? Allowed: 10 Allowed: 20 Allowed: 30 Not Allowed: 40

Answer 29

int {int} switchport trunk allowed vlan 10,20,30 We don't include 40 because it's not allowed

Question 30

If two switches are cabled together in the right circumstances they can negotiate a trunk using what?

Answer 30

Cisco's Dynamic Trunking Protocol

Question 31

What is switchport mode dynamic auto?

Answer 31

This command will form a trunk IF the neighbor switch port is set to trunk or switchport mode dynamic desirable

Question 32

This will form a trunk if the neighbor switch port is set to trunk, desirable or auto. Default on older switches.

Answer 32

sw mode trunk or switchport mode dynamic desirable

Question 33

How would you disable DTP?

Answer 33

switchport nonegotiate

Question 34

What command would you enter to check the administrative mode on a switchport?

Answer 34

show int {int} switchport

Question 35

What 2 items would be in the Operational Mode of a show int switchport command?

Answer 35

It will show whether it's a Trunk or Access port

Question 36

What 2 items would be in the Administrative Mode of a show int switchport command?

Answer 36

Dynamic Auto or Dynamic Desirable

Question 37

An Access port is considered what type of port?

Answer 37

An untagged port

Question 38

A Trunk port is considered what type of port?

Answer 38

A tagged port

Question 39

Do untagged packets contain a VLAN tag?

Answer 39

No

Question 40

How many VLANs can an untagged port belong to?

Answer 40

1

Question 41

True or False - A tagged port can send both untagged and tagged packets

Answer 41

True

Question 42

When a tagged port receives an untagged packet it does what?

Answer 42

It applies its native VLAN to that packet

Question 43

When an untagged port (Access Port) receives a Tagged Packet (Containing a VLAN Tag) the switch will do what?

Answer 43

Send it out the port with that VLAN tag or it will drop the packet if the VLAN tag on the packet is not the same as the VLAN configured on that port

Question 44

Packets that match the native VLAN configured on a tagged port are sent out as what?

Answer 44

Untagged packet because the tagged port will strip the dot1q header off as it sends it out to the switchport

Question 45

What is the default DTP mode on modern switches?

Answer 45

Switchport mode dynamic auto

Question 46

What does VTP stand for?

Answer 46

VLAN Trunking Protocol

Question 47

What is VTP used for?

Answer 47

VTP allows you to add, edit or delete VLANs on switches configured as VTP Servers and have other switches configured as VTP Clients sync their VLAN database with the Server

Question 48

Will a transparent mode VTP switch get updated with the Server's VLAN database?

Answer 48

No, transparent mode will not update anything that the Server mode switch pushes

Question 49

How do you configure a VTP mode server?

Answer 49

config mode vtp domain {domain-name} vtp mode server

Question 50

How do you configure a VTP mode client?

Answer 50

config mode vtp mode client

Question 51

How do you configure a VTP mode transparent switch?

Answer 51

config mode vtp mode transparent

Question 52

If you want a transparent switch to know about the VLANs in a network, what do you need to do?

Answer 52

Manually add the VLANs because since it's in transparent mode it will not receive VLAN database info from the server mode switch

Question 53

How would you verify VTP?

Answer 53

show vtp status

Question 54

If you wanted to, could you manually add, edit or delete VLAN database info on a Client mode switch?

Answer 54

No, that has to come the server mode switch

Question 55

What 3 types of InterVLAN routing are there?

Answer 55

1. Router with Separate Interfaces 2. Router on a Stick 3. Layer 3 Switch Routing

Question 56

What are the commands to configure Layer 3 Switching on a non-WAN configuration?

Answer 56

ip routing int vlan {vlan-id) (this creates the SVI) ip address {ip-address} {subnet-mask}

Question 57

What are the commands to configure WAN Layer 3 Routing on a Switch?

Answer 57

int {int} no switchport ip address {ip-address} {subnet-mask} then include that port in a network statement for a routing protocol or use a static route

Question 58

Assigning IP Addresses to an interface in the same subnet as other connected devices on the Router and then tagging them in the proper VLAN on the switch as an access port is considered what type of InterVLAN routing?

Answer 58

Router with Separate Interfaces

Question 59

Why is Router with Separate Interfaces considered bad practice?

Answer 59

Because you'll quickly run out of interfaces to use on the router

Question 60

What commands would be used to configure Router with Separate Interfaces?

Answer 60

On the Router: int {int} ip address {ip-address} {subnet-mask} On the Switch: sw mode acc sw acc vlan {vlan}

Question 61

For Router on a Stick to work the cable going from the Switch to the Router has to be a what?

Answer 61

A Trunk Port

Question 62

What does a Subinterface look like on a Router?

Answer 62

int fa0/1.10 or even int gi0/2.20

Question 63

What are the commands to configure Router on a Stick on the Router and the Switch?

Answer 63

Router int {int} no ip address no shut exit out of the int int {sub-interface} -- Ex: int fa0/1.10 encapsulation dot1q 10 ip address {ip-address} {subnet-mask} (This will be the gateway address for that VLAN) On the Switch int {int} sw mode trunk

Question 64

What are the general steps to create a VLAN and have it configured for interVLAN routing and WAN routing to other sites?

Answer 64

1. Create the VLAN 2. Enable IP Routing 3. Create the SVI and IP it w/ a subnet mask 4. Configure the Layer 3 interface to have it be a no switchport and add an IP Address and add a subnet mask to it 5. Include that Layer 3 interface in a routing protocol or a static route