Chapter 1 – Implement VLAN based solution, given a network design and a set of requirements
QUESTION NO: 36
The Company core switches use 802.1Q trunks to connect to each other. How does 802.1Q trunking keep track of multiple VLANs?
A. It tags the data frame with VLAN information and recalculates the CRC value
B. It encapsulates the data frame with a new header and frame check sequence
C. It modifies the port index of a data frame to indicate the VLAN
D. It adds a new header containing the VLAN ID to the data frame
E. None of the other alternatives apply
Answer: A
Explanation:
The IEEE 802.1Q protocol can also carry VLAN associations over trunk links. However, this frame identification method is standardized, allowing VLAN trunks to exist and operate between equipment from multiple vendors.
In particular, the IEEE 802.1Q standard defines an architecture for VLAN use, services provided with VLANs, and protocols and algorithms used to provide VLAN services. Like Cisco ISL, IEEE 802.1Q can be used for VLAN identification with Ethernet trunks. Instead of encapsulating each frame with a VLAN ID header and trailer, 802.1Q embeds its tagging information within the Layer 2 frame. This method is referred to as single-tagging or internal tagging. 802.1Q also introduces the concept of a native VLAN on a trunk. Frames belonging to this VLAN are not encapsulated with any tagging information. In the event that an end station is connected to an 802.1Q trunk link, the end station can receive and understand only the native VLAN frames. This provides a simple way to offer full trunk encapsulation to the devices that can understand it, while giving normal access stations some inherent connectivity over the trunk.
QUESTION NO: 37
Refer to the exhibit. On the basis of the output generated by the show commands, which two statements are true? (Choose two.)
A. Because it is configured as a trunk interface, interface gigabitethernet 0/1 does not appear in the show vlan output.
B. VLAN 1 will not be encapsulated with an 802.1q header.
C. There are no native VLANs configured on the trunk.
D. VLAN 2 will not be encapsulated with an 802.1q header.
E. All interfaces on the switch have been configured as access ports.
F. Because it has not been assigned to any VLAN, interface gigabitethernet 0/1 does not appear in the show vlan output.
Answer: A,B
Explanation:
The IEEE 802.1Q protocol can also carry VLAN associations over trunk links. However, this frame identification method is standardized, allowing VLAN trunks to exist and operate between equipment from multiple vendors. In particular, the IEEE 802.1Q standard defines an architecture for VLAN use, services provided with VLANs, and protocols and algorithms used to provide VLAN services. Like Cisco ISL, IEEE 802.1Q can be used for VLAN identification with Ethernet trunks. Instead of encapsulating each frame with a VLAN ID header and trailer, 802.1Q embeds its tagging information within the Layer 2 frame. This method is referred to as single-tagging or internal tagging. 802.1Q also introduces the concept of a native VLAN on a trunk. Frames belonging to this VLAN are not encapsulated with any tagging information. In the event that an end station is connected to an 802.1Q trunk link, the end station can receive and understand only the native VLAN frames. This provides a simple way to offer full trunk encapsulation to the devices that can understand it, while giving normal access stations some inherent connectivity over the trunk. show vlan: This commands shows the vlan, ports belonging to VLAN means that port on access mode. It doesn’t show the port on trunk mode.
QUESTION NO: 38
Which three statements are correct with regard to the IEEE 802.1Q standard? (Choose three.)
A. The IEEE 802.1Q frame format adds a 4 byte field to a Ethernet frame
B. The packet is encapsulated with a 26 byte header and a 4 byte FCS
C. The protocol uses point-to-multipoint connectivity
D. The protocol uses point-to-point connectivity
E. The IEEE 802.1Q frame uses multicast destination of 0x01-00-0c-00-00
F. The IEEE 802.1Q frame retains the original MAC destination address
Answer: A,D,F
Explanation:
The IEEE 802.1Q protocol can also carry VLAN associations over trunk links. However, this frame identification method is standardized, allowing VLAN trunks to exist and operate between equipment from multiple vendors. In particular, the IEEE 802.1Q standard defines an architecture for VLAN use, services provided with VLANs, and protocols and algorithms used to provide VLAN services. Like Cisco ISL, IEEE 802.1Q can be used for VLAN identification with Ethernet trunks. Instead of encapsulating each frame with a VLAN ID header and trailer, 802.1Q embeds its tagging information within the Layer 2 frame. This method is referred to as single-tagging or internal tagging.
802.1Q also introduces the concept of a native VLAN on a trunk. Frames belonging to this VLAN are not encapsulated with any tagging information. In the event that an end station is connected to an 802.1Q trunk link, the end station can receive and understand only the native VLAN frames. This provides a simple way to offer full trunk encapsulation to the devices that can understand it, while giving normal access stations some inherent connectivity over the trunk.
QUESTION NO: 39
Switch R1 has been configured with DTP using the desirable option. Which statement describes Dynamic Trunking Protocol (DTP) desirable mode?
A. The interface actively attempts to convert the link to a trunk link.
B. The interface is put into permanent trunking mode but prevented from generating DTP frames.
C. The interface is put into permanent trunking mode and negotiates to convert the link into a trunk link.
D. The interface is put into a passive mode, waiting to convert the link to a trunk link.
E. None of the other alternatives apply
Answer: A
Explanation: In the switchport mode command, you can set the trunking mode to any of the following:
QUESTION NO: 40
Which switch command enables a trunking protocol that appends a four byte CRC to the packet?
A. CompanySwitch(config-if)#switchport trunk encapsulation dot1q
B. CompanySwitch(config-if)#switchport trunk encapsulation itef
C. CompanySwitch(config-if)#switchport trunk encapsulation fddi
D. CompanySwitch(config-if)#switchport trunk encapsulation isl
E. None of the other alternatives apply
Answer: D
Explanation:
The Inter-Switch Link (ISL) protocol is a Cisco proprietary method for preserving the source VLAN identification of frames passing over a trunk link. ISL performs frame identification in Layer 2 by encapsulating each frame between a header and trailer. Any Cisco switch or router device configured for ISL can process and understand the ISL VLAN information. ISL is primarily used for Ethernet media, although Cisco has included provisions to carry Token Ring, FDDI, and ATM frames over Ethernet ISL. (A Frame-Type field in the ISL header indicates the source frame type.) When a frame is destined out a trunk link to another switch or router, ISL adds a 26-byte header and a 4-byte trailer to the frame. The source VLAN is identified with a 10-bit VLAN ID field in the header. The trailer contains a cyclic redundancy check (CRC) value to ensure the data integrity of the new encapsulated frame. Figure 6-3 shows how Ethernet frames are encapsulated and forwarded out a trunk link. Because tagging information is added at the beginning and end of each frame, ISL is sometimes referred to as double tagging.
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