2.1 VLANs Flashcards
Configure and verify VLANs (normal range) spanning multiple switches, including access ports (data and voice), default VLAN, and InterVLAN connectivity. (30 cards)
Define:
VLAN
A logical grouping of network devices.
VLANs allow for network segmentation, improving security, reducing broadcast traffic, and simplifying network management. They enable devices on different physical networks to communicate as if they were on the same network.
List the types of VLANs commonly used in networks.
- Default VLAN
- Data VLAN
- Voice VLAN
- Management VLAN
- Native VLAN
Default VLAN: The VLAN assigned to all ports by default, typically VLAN 1.
Data VLAN: Used for user traffic and general network communication.
Voice VLAN: Dedicated to VoIP traffic to prioritize voice communication.
Management VLAN: Used for network management and monitoring traffic.
Native VLAN: Handles untagged frames on a trunk link, usually VLAN 1 by default.
What is the default VLAN for all ports on a Cisco switch?
VLAN 1
By default, all ports on a Cisco switch are assigned to VLAN 1 unless otherwise configured. This is a standard setting across Cisco devices.
What is VLAN trunking?
A method for carrying traffic from multiple VLANs over a single link.
Trunking is essential for inter-switch communication, enabling VLAN traffic to be transmitted across switches using protocols like 802.1Q.
Fill in the blank:
The protocol used for VLAN trunking in modern networks is ________.
802.1Q
802.1Q is the industry-standard protocol for VLAN tagging, allowing multiple VLANs to be carried over a single trunk link.
What is the size of the VLAN ID field in the 802.1Q header?
12 bits
The VLAN ID field occupies 12 bits within the 4-byte header of the 802.1Q protocol, which is used for tagging frames in a network.
True or False:
The default VLAN is always VLAN 2 on Cisco switches.
False
The default VLAN on Cisco switches is VLAN 1, not VLAN 2. It cannot be deleted, though it can be reassigned.
Fill in the blank:
A switch forwards a frame lacking an _______ header on a trunk.
802.1Q
Frames without an 802.1Q header are sent to the native VLAN, which defaults to VLAN 1.
If a switch has two broadcast domains, how many VLANs does it have?
Two
Each broadcast domain corresponds to a VLAN. Therefore, two broadcast domains indicate the presence of two VLANs.
What can be said about the VLAN ID of a native VLAN?
It can have its VLAN ID changed and is VLAN 1 by default.
A native VLAN can be configured to any VLAN ID, but it starts as VLAN 1 by default.
How can broadcast traffic be reduced in a multi-department network?
By implementing VLANs.
VLANs create separate broadcast domains, which limits broadcast traffic to only the relevant department, thus reducing overall network congestion.
True or False:
A Layer 2 switch can’t forward traffic between VLANs without a router.
True
A Layer 2 switch cannot route traffic between VLANs; InterVLAN routing requires either a router or a Layer 3 switch.
What are the four components found in the tag of an 802.1Q frame.
- VID (VLAN Identifier)
- CFI (Canonical Format Indicator)
- PRI (Priority)
- TPID (Tag Protocol Identifier)
VID: Identifies the VLAN to which the frame belongs.
CFI: Indicates the MAC address format.
PRI: Specifies the priority level for the frame.
TPID: Marks the frame as an 802.1Q tagged frame.
What are the characteristics of access interfaces on a switch?
They do not use VLAN trunking and are configured for one VLAN only.
Access ports are dedicated to a single VLAN and do not participate in trunking, which is reserved for inter-switch connections.
Which subfield in an 802.1Q frame identifies the VLAN?
VID
The VLAN Identifier (VID) is crucial for specifying the VLAN to which the frame belongs, allowing for proper traffic management.
What are two identifying features of a switch’s default VLAN?
It cannot have its VLAN ID changed and has a default VLAN ID of 1.
The default VLAN remains at ID 1 and cannot be modified; it is essential for basic switch operations.
True or False:
VLAN 1 is the default VLAN for interfaces and cannot be deleted.
True
VLAN 1 is a fundamental component of Cisco switches, serving as the default and undeletable VLAN.
Fill in the blank:
VLANs ______ CPU workload on network devices.
reduce
By isolating broadcast domains, VLANs ensure that devices only process relevant broadcasts, preventing unnecessary processing of every broadcast frame and improving overall performance.
What command is used to designate VLAN 2 as the native VLAN on a switch?
switchport trunk native vlan 2.
This command configures the specified VLAN as the native VLAN for trunk ports, allowing untagged traffic to flow correctly.
Which command checks a switch interface’s administrative mode?
show interfaces gigabit 0/1 switchport.
This command provides detailed information about the specified interface, including its VLAN configuration.
How many VLANs are available by default on a Cisco switch?
5
Cisco switches come with five default VLANs: 1, 1002, 1003, 1004, and 1005, with VLAN 1 being the active default for interfaces.
List three advantages of implementing VLANs in a network.
- Flexible network design.
- Improved security by isolating VLAN traffic.
- Fewer hosts processing unnecessary broadcasts.
VLANs allow for organized traffic management, improved security, and decreased unnecessary load on devices.
How can you delete a VLAN from a Cisco switch?
By using the command “no vlan [VLAN_ID]”.
This command removes the VLAN configuration, but you may also need to remove the VLAN from any trunk configurations to fully delete it.
Which command configures an access port for VLAN 10, ignoring DTP?
switchport mode access.
This command ensures the port operates solely as an access interface, preventing it from being influenced by trunking protocols.
