Module 5 notes

What is a VLAN?

A logical network that separates devices into different broadcast domains.

What does VLAN stand for?

Virtual Local Area Network

At which OSI layer do VLANs primarily operate?

Layer 2 (Data Link)

What type of domain does each VLAN create?

A separate broadcast domain

What device is needed for communication between different VLANs?

A router or Layer 3 switch

What is inter-VLAN routing?

Routing traffic between different VLANs.

Can devices on different switches communicate within the same VLAN?

Yes, through a VLAN trunk.

How are devices grouped into VLANs regardless of physical location?

By function, department, or application.

What happens when a device sends a broadcast within a VLAN?

Only devices in that VLAN receive it.

What happens to broadcasts when multiple IP subnets share one VLAN?

They reach all devices in that VLAN.

What is the main performance benefit of VLANs?

Reduced unnecessary broadcast traffic

How do VLANs improve network security?

By isolating traffic between groups of devices.

How do VLANs improve IT efficiency?

By grouping devices with similar network requirements.

How do VLANs reduce network costs?

By using existing infrastructure more efficiently.

How do VLANs simplify application management?

By separating users and resources by function.

What addressing approach should VLAN design consider?

Hierarchical IP addressing

What is hierarchical IP addressing?

Organizing IP address blocks by network segment or location.

How many VLANs are needed to create three separate broadcast domains?

Three VLANs

What VLAN is assigned to Cisco switch ports by default?

VLAN 1

What is the default native VLAN on Cisco switches?

VLAN 1

What is the default management VLAN on a Cisco Layer 2 switch?

VLAN 1

Which VLAN cannot be deleted or renamed on a Cisco switch?

VLAN 1

What type of traffic does a data VLAN carry?

User-generated data traffic

What is another name for a data VLAN?

User VLAN

What type of traffic should be separated from data VLANs?

Voice and network management traffic

What is the purpose of a native VLAN?

To carry untagged traffic on an 802.1Q trunk.

What happens to an untagged frame received on an 802.1Q trunk?

It is assigned to the native VLAN.

What is a recommended security practice for native VLANs?

Use an unused VLAN other than VLAN 1.

Why should the native VLAN be separated from the management VLAN?

To reduce security risks.

What is a management VLAN?

A VLAN dedicated to managing network devices.

What protocol provides encrypted command-line management of switches?

SSH

What protocol provides unencrypted remote command-line management?

Telnet

What protocol provides encrypted web-based device management?

HTTPS

What protocol is commonly used to monitor network devices?

SNMP

What is the purpose of a voice VLAN?

To carry VoIP traffic separately from data traffic.

What does VoIP stand for?

Voice over Internet Protocol

Why does VoIP traffic need priority over regular data?

To minimize delay and maintain call quality.

What is the recommended maximum one-way delay for VoIP traffic?

Less than 150 milliseconds

What Cisco protocol can inform an IP phone about its voice VLAN?

CDP

Can a Cisco switch port support both a PC and an IP phone using different VLANs?

Yes, with a data VLAN and a voice VLAN.

What is a VLAN trunk?

A link that carries traffic for multiple VLANs.

What is the main purpose of VLAN trunking?

To extend VLANs across network devices.

What IEEE standard is used for Ethernet VLAN tagging?

IEEE 802.1Q

What type of connection is a trunk link?

A point-to-point link between network devices.

Does a trunk port belong to only one data VLAN?

No, it carries multiple VLANs.

Which VLANs are allowed on a Cisco trunk by default?

All VLANs

What is an access port?

A switch port that normally carries one data VLAN.

What is the main difference between access and trunk ports?

Access ports carry one data VLAN; trunks carry multiple VLANs.

What is VLAN tagging?

Adding VLAN identification information to Ethernet frames.

Why is VLAN tagging necessary on trunk links?

To identify which VLAN each frame belongs to.

How many bytes does an IEEE 802.1Q VLAN tag add?

4 bytes

Where is the 802.1Q tag inserted in an Ethernet frame?

Between the source MAC address and Type/Length field.

What does TPID stand for?

Tag Protocol Identifier

What is the standard Ethernet TPID hexadecimal value?

0x8100

How large is the TPID field in an 802.1Q tag?

2 bytes

How many bits are used for the 802.1Q priority field?

3 bits

What is the purpose of the 802.1Q priority field?

To identify traffic priority.

What does CFI stand for?

Canonical Format Identifier

How many bits are used for the CFI field?

1 bit

How many bits identify the VLAN ID in an 802.1Q tag?

12 bits

How many VLAN ID values can a 12-bit field represent?

4096

What does FCS stand for?

Frame Check Sequence

What happens to the FCS when a switch inserts an 802.1Q tag?

It is recalculated.

What does PVID stand for?

Port VLAN Identifier

What does the PVID identify on an 802.1Q trunk?

The VLAN assigned to untagged incoming frames.

What is the default PVID on a Cisco trunk?

VLAN 1

If VLAN 99 is the native VLAN, where does incoming untagged traffic go?

VLAN 99

What can happen if a Cisco trunk receives a tagged frame for its native VLAN?

The frame may be dropped.

What happens when untagged traffic enters an unused native VLAN with no forwarding path?

The frame is dropped.