VLANs Flashcards
What OSI Layer do VLANs live at?
Layer 2
True or False - Switches do not forward broadcast traffic by default
False. They do forward broadcast traffic by default
True or False - Switches forward broadcast traffic everywhere, including between IP Subnets
True
What kind of traffic were VLANs designed to segment?
Broadcast Traffic
What does broadcast traffic on a switch bypass?
It bypasses the router and/or the firewall because it’s a Layer 2 broadcast
VLANS segment the LAN into what?
Separate Broadcast Domains
If you have VLANs set up on a switch, the switch will only allow traffic within the same what?
VLAN
How would you create a VLAN on a switch?
vlan {vlan #id}
vlan {name}
How would you put an interface in a specific VLAN?
int {int}
switchport mode access
switchport acc vlan {vlan-id}
How would you configure a range of interfaces from fa0/1 to fa0/5 to go in a VLAN?
int range fa0/1 - 5
sw mode access
sw acc vlan {vlan #id}
What is the command to verify which ports are in specific VLANs?
show vlan brief
What is the command to view specific information about a switchport?
show int {int} switchport
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?
No, unicast traffic between subnets still need a router to get to where it’s going
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?
Yes, broadcast traffic, regardless of what subnet the device is in, will get forwarded out ALL ports on the switch.
Do switches send traffic between multiple VLANs?
No, routers do this
What encapsulation mode is a VLAN Trunk configured in?
Dot1Q
Why would you want to have trunk ports between switches?
So that your devices can talk to other devices in their same VLAN on other switches.
What happens to the Layer 2 header when it forwards traffic to another switch for the same VLAN?
It tags the Layer 2 Dot1Q header with the correct VLAN
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?
Only ports configured in VLAN 299
What happens when a switch forwards traffic tagged with a Dot1Q VLAN out to an access port?
It strips the Layer 2 Dot1Q tag. The end device isn’t VLAN aware so it wouldn’t know what do with it
Scenario: If you have a server with multiple VMs running in multiple different VLANs, what should you make sure of?
You need to have the link between the switch and the server trunked
True or False - For a phone that is daisychained, you only need to have the voice vlan command configured
False. You need to the port configured in access mode and also the access vlan designation as well
How would you configure a trunkport?
int {int}
description {description of trunk port}
switchport trunk encapsulation dot1q (modern switches don’t require this command)
switchport mode trunk
Do you need to configure both sides of the link to be a trunk?
Yes
What is the default native VLAN?
1