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642-813 Q&A – Implement VLAN based solution (66-70)

Section 1 – Implement VLAN based solution, given a network design and a set of requirements

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?
C. 802.1Q
E. None of the other alternatives apply

Answer: C
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 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.

Refer to the exhibit. Based upon the output of show vlan on switch CAT2, what can we conclude about interfaces Fa0/13 and Fa0/14?

A. that interfaces Fa0/13 and Fa0/14 are in VLAN 1
B. that interfaces Fa0/13 and Fa0/14 are down
C. that interfaces Fa0/13 and Fa0/14 are trunk interfaces
D. that interfaces Fa0/13 and Fa0/14have a domain mismatch with another switch
E. that interfaces Fa0/13 and Fa0/14have a duplex mismatch with another switch
Answer: C
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.
show vlan: This commands shows the vlan, ports belonging to VLAN means that port on access mode. It doesn’t shows the port on trunk mode.

You need to investigate a VTP problem between two Company switches. The lack of which two prevents VTP information from propagating between switches? (Select two)
A. A root VTP server
B. A trunk port
C. VTP priority
E. None of the other alternatives apply
Answer: B,D
In Switch two types of links are available, access and trunk. The interface is in access mode can carry the information of only one VLAN and trunk can carry the information of more than one VLAN. VTP carry the information of more than one vlan so Switch port should be in trunk mode.
VLAN1 is the default VLAN on Cisco Switch, by default all interface belongs to VLAN 1.

By default, all VLANs will belong to which MST instance when using Multiple STP?
A. MST00
B. MST01
C. the last MST instance configured
D. none
Answer: A
Recall that the whole idea behind MST is the capability to map multiple VLANs to a smaller number of STP instances. Inside a region, the actual MST instances (MSTIs) exist alongside the IST. Cisco supports a maximum of 16 MSTIs in each region. IST always exists as MSTI number 0, leaving MSTI 1 through 15 available for use. By default all VLANs are belonged to MST00 instance.

If you needed to transport traffic coming from multiple VLANs (connected between switches), and your CTO was insistent on using an open standard, which protocol would you use?
A. 802.11B
B. spanning-tree
C. 802.1Q
F. Q.921
Answer: C
The act involved in the above question is trunking. The two trunking protocols in the answer choices are: 802.1Q and ISL. ISL is Cisco proprietary and IEEE 802.1Q is based on an open standard. When non-Cisco switches are used along with Cisco switches and trunking is required, it is best to use the 802.1Q encapsulation.
Incorrect Answers:
A: This standard is used in wireless networking and has nothing to do with VLAN switching.
B: The Spanning Tree Protocol (STP) is used to prevent loops within a bridged network. Each
VLAN runs a separate instance of the STP and this is enabled by default.
D: This is the alternative Cisco proprietary method of trunking.
E: VLAN Trunking Protocol (VTP) is a Layer 2 messaging protocol that manages the addition, deletion, and renaming of VLANs on a network-wide basis. It is not used to actually transport VLAN traffic.
F: This is an ISDN signaling standard and is not related with VLAN switching.