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30 Cards in this Set

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VLAN Tagging
VLAN tagging is where the sending switch adds another header to the frame before sending it over the trunk.

The extra header includes a VLAN identifier (VLAN ID) field so that the sending switch can list the VLAN ID and the receiving switch can then know in what VLAN each frame belongs.

This header typically encapsulates the original Frame, which remains unchanged. Once the Switch knows the appropriate VLAN, the additional header is discarded, and the frame is delivered as normal.
ISL Trunking Standard
ISL is a Cisco propriety Trunking Standard. Some newer Cisco switches do not support it, as 802.1Q is much more popular.

ISL fully encapsulates each original Ethernet frame in an ISL header and trailer. The original frame remains unchanged.

The ISL header is 26 Bytes, and the trailer with CRC is 4 Bytes.
IEEE 802.1Q
IEEE 802.1Q is the standard trunking protocol today.

802.1Q does not actually encapsulate the original frame in another header and trailer. Instead, it inserts and extra 4-byte VLAN header into the original frame's Ethernet header. It retains the original source and destination MAC addresses.
How many VLANs are supported by trunking protocols?

1 - 1005 is the normal range, and higher is the extended range. The distinction matters for VTP
Native VLAN
802.1Q defines one VLAN on each trunk as the native VLAN.

By default, the native VLAN is 1. If a switch receives a frame that does not have an 802.1Q header, the receiving switch knows that the frame is part of the native VLAN.

This allows the switch to support connections to devices that do not understand trunking. A switch that does not understand 802.1Q, can send frames with no trunking headers, and the other switch would understand the frame. This allows some basic functions (like telnet) to function.
VLAN Trunking Protocol (VTP)
VTP is a Cisco proprietary trunking protocol for switches to exchange VLAN configuration information.

VTP advertises each VLAN ID and VLAN name, but does not advertise the details about which interfaces are assigned to each VLAN.

VTP defines a Layer 2 protocol that the switches use to exchange VLAN configuration information. VTP causes the switches to synchronize their VLAN configuration to include the same VLAN IDs and VLAN names.
What are the 3 VTP Modes?
Server Mode

Client Mode

Transparent Mode
What is the purpose of VTP Transparent Mode?
VTP cannot be disabled on Cisco switches, so Transparent mode means the switch will ignore VTP, other than to forward VTP messages so that any other clients or servers can receive a copy.
VTP Server Mode
VTP Server is the device that sends out the VLAN information.
VLAN database configuration revision number
VTP Clients and Servers use the VLAN database configuration revision number to choose whether to react to a received VTP update.

Each time a VTP Server modifies its VLAN configuration, the VTP Server increments the current configuration revision number by 1.

If the revision number is higher than its own, the switch updates its VLAN configuration. The complete sequence is called synchronization.
Types of VTP messages
1. Summary Advertisements

Summary Advertisements list the revision number, domain name, and other information, but no VLAN information. These occur every 5 minutes by default.

2. Subset Advertisements

If something changes, the summary advertisement advertises some subset of the VLAN database.

3. Advertisement Request Message

The advertisement request message allows a switch to immediately request VTP messages from a neighboring switch as soon as a trunk comes up.
3 requirements for VTP to work between two switches
1. The link between the switches must be operating as a VLAN trunk (ISL or 802.1Q).

2. The two switches' case sensitive VTP domain name must match.

3. If configured on at least one of the switches, the the two switches VTP password must match. The VTP password protects against attackers forcing a switch to change its VLAN configuration.
VTP Domains
VTP Domains allow for the creation of multiple groups of VTP switches, called domains, whose VLAN configurations are autonomous.

One set of switches in one VTP domain and another set in another VTP domain, and switches in the different domains will ignore each other's VTP messages.
How are VLAN configurations stored?
VLAN Configurations are stored in Flash. The file is ' vlan.dat '.

Cisco IOS does not store VLAN configurations in the running or startup config.

Storing the configuration in flash in the vlan.dat file allows both clients and servers to dynamically learn about VLANs and have the configuration automatically stored, making both client and server prepared for their next reload.
VTP Pruning
VTP Pruning allows VTP to dynamically determine which switches do not need frames from certain VLANs, and then VTP prunes those VLANs from the appropriate trunks.

This means that switch trunk interfaces do not flood frames in that VLAN. This increases the available bandwidth by restricting flooded traffic.
What is the command to configure a new VLAN?
vlan ## vlan id ##

global configuration command
How is a VLAN name assigned?
From the VLAN configuration, the command is:

name ##name##
How do you assign an interface to a VLAN?
switchport access vlan ## id number ##

If there is not a VLAN created with that number, then it will be created. If one exists, the interface will be added to that VLAN.
What is the command to disable trunking?
switchport mode access
What are the Cisco switch defaults regarding VLANs and VTP?
- VTP Server mode

- No VTP domain name

- VLAN 1 and VLANs 1002 - 1005 are automatically configured and cannot be deleted

- All access interfaces are assigned to VLAN1
Dynamic Trunk Protocol (DTP)
Switches will negotiate the type of trunking with the switch on the other end of the trunk.
If both switches support ISL and 802.1Q, the switches will negotiate 802.1Q by default.

(True of false)

If both switches support ISL, then they will negotiate that.
What is the command to set the trunking encapsulation type?
switchport trunk encapsulation {dot1q | isl | negotiate}

switches default to 'switchport trunk encapsulation dot1q'
What are the 4 options for the 'Switchport mode' command?
- access - prevents the use of trunking, making the port always act as an access (nontrunk) port

- trunk - always uses trunking

- dynamic desirable - initiates negotiation messages and responds to negotiation messages to dynamically choose whether to start using trunking and defines the trunking encapsulation

- dynamic auto - passively waits to receive trunk negotiation messages, at which point the switch will respond and negotiate whether to use trunking, and if so, the type of trunking - this is the default
What is the command to modify the 'allowed VLAN list'?
switchport trunk allowed vlan {add | all | except | remove} ##vlan-list##

- 'add' adds VLANs to the existing allowed VLAN list

- 'remove' removes VLANs from the existing list

- 'all' adds all VLANs, effectively returning to the original settings

- 'except' adds all VLANs that are not part of the command
What VLANs show up in the 'show interfaces trunk' command?
- VLANs in the allowed VLAN list

- VLANs that are configured and active (not shutdown)

- VLANs that are not pruned and are in an STP forwarding state
Voice Gateway
Voice gateways connect to the existing, traditional telephone network.
Cisco IP Phone trunking
Links between IP Phones and the switch use 802.1Q trunking, and the phone and PC should be in different VLANs.
What is the command to configure the 'switchport voice vlan' ?
switchport voice vlan ##vlan id##
What is the command to set the VTP mode?
vtp mode {server | client}