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16.
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 & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| In the switchport mode command, you can set the trunking mode to any of the following: trunk - This setting places the port in permanent trunking mode. The corresponding switch port at the other end of the trunk should be similarly configured because negotiation is not allowed. You should also manually configure the encapsulation mode. dynamic desirable (the default)-The port actively attempts to convert the link into trunking mode. If the far-end switch port is configured to trunk , dynamic desirable , or dynamic auto mode, trunking is successfully negotiated. dynamic auto -The port converts the link into trunking mode. If the far-end switch port is configured to trunk or dynamic desirable , trunking is negotiated. Because of the passive negotiation behavior, the link never becomes a trunk if both ends of the link are left to the dynamic auto default. |
17.
You need to configure a new Company switch for trunking. 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 & Explanation
- Report
Answer : [D]
Explanation :
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 . |
18.
While using a packet analyzer, you notice four additional bytes being added to the packets in the
Company network. Which protocol inserts a four byte tag into the Ethernet frame and recalculates
CRC value?
- A.DTP
- B.VTP
- C.802.1Q
- D.ISL
- E.None of the other alternatives apply.
- Answer & Explanation
- Report
Answer : [C]
Explanation :
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. |
19.
You need to configure a new Company switch to support DTP. Which DTP switchport mode
parameter sets the switch port to actively send and respond to DTP negotiation frames?
- A.Access
- B.No negotiate
- C.Trunk
- D.Dynamic desirable
- E.Dynamic auto
- F.None of the other alternatives apply
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| dynamic desirable (the default)-The port actively attempts to convert the link into trunking mode. If the far-end switch port is configured to trunk , dynamic desirable , or dynamic auto mode, trunking is successfully negotiated. |
20.
A new Company switch was just configured using the "switchport trunk native vlan 7" command.
What does this interface command accomplish?
- A.Causes the interface to apply ISL framing for traffic on VLAN 7
- B.Configures the trunking interface to forward traffic from VLAN 7
- C.Configures the interface to be a trunking port and causes traffic on VLAN 7 to be 802.1q tagged
- D.Configures the trunking interface to send traffic from VLAN 7 untagged
- E.None of the other alternatives apply
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
|
In 802.1Q trunking, all VLAN packets are tagged on the trunk link to indicate the VLAN to which
they belong. Frames belonging to the Native VLAN are sent untagged on the trunk link. The Native
VLAN contains ports not assigned to other VLANs that by default belong to VLAN 1. VLAN 1 is the
Native VLAN by default, but VLANs other than VLAN 1 may be designated as the Native VLAN.
However, the Native VLAN must be the same on trunked switches in 802.1Q trunking. If a VLAN
other than VLAN 1 is to be the Native VLAN, it needs to be identified on the trunk ports. In the
interface configuration mode of the trunk port(s), the IOS-based command to designate the Native
VLAN is switchport trunk native . Switch( config-if)# switchport trunk native vlan vlan-id |
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