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642-813 Q&A – Implement VLAN based solution (41-45)

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

Company uses MSTP within their switched LAN. What is the main purpose of Multiple Instance Spanning Tree Protocol (MSTP)?
A. To enhance Spanning Tree troubleshooting on multilayer switches
B. To reduce the total number of spanning tree instances necessary for a particular topology
C. To provide faster convergence when topology changes occur in a switched network
D. To provide protection for STP when a link is unidirectional and BPDUs are being sent but not received
E. None of the other alternatives apply
Answer: B

MST is built on the concept of mapping one or more VLANs to a single STP instance. Multiple instances of STP can be used (hence the name MST), with each instance supporting a different group of VLANs.
Each could be tuned to result in a different topology, so that Instance 1 would forward on the left uplink, while Instance 2 would forward on the right uplink. Therefore, VLAN A would be mapped to Instance 1, and VLAN B to Instance 2.
To implement MST in a network, you need to determine the following: The number of STP instances needed to support the desired topologies. Whether to map a set of VLANs to each instance.

Refer to the exhibit. The user who is connected to interface FastEthernet 0/1 is on VLAN 10 and cannot access network resources. On the basis of the information in the exhibit, which command sequence would correct the problem?

A.SW1(config)# vlan 10
SW1(config-vlan)# no shut
B.SW1(config)# interface fastethernet 0/1
SW1(config-if)# switchport mode access
SW1(config-if)# switchport access vlan 10
C.SW1(config)# interface fastethernet 0/1
SW1(config-if)# switchport mode access
D.SW1(config)# vlan 10
SW1(config-vlan)# state active
E.SW1(config)# interface fastethernet 0/1
SW1(config-if)# no shut
Answer: E

Switch R1 and R2 both belong to the Company VTP domain. What’s true about the switch operation in VTP domains? (Select all that apply)
A. A switch can only reside in one management domain
B. A switch is listening to VTP advertisements from their own domain only
C. A switch is listening to VTP advertisements from multi domains
D. A switch can reside in one or more domains
E. VTP is no longer supported on Catalyst switches
Answer: A,B
A VTP domain is made up of one or more interconnected devices that share the same VTP domain name. A switch can be configured to be in only one VTP domain, and each VLAN has a name that is unique within a management domain.
Typically, you use a VTP domain to ease administrative control of your network or to account for physical boundaries within your network. However, you can set up as many or as few VTP domains as are appropriate for your administrative needs. Consider that VTP is transmitted on all trunk connections, including ISL, IEEE 802.1Q, 802.10, and LANE.
Switches can only belong to one management domain with common VLAN requirements, and they only care about the neighbors in their own domains.

Refer to the exhibit. VTP has been enabled on the trunk links between all switches within the TEST domain. An administrator has recently enabled VTP pruning. Port 1 on Switch 1 and port 2 on Switch 4 are assigned to VLAN 2. A broadcast is sent from the host connected to Switch 1. Where will the broadcast propagate?

A. Every switch in the network receives the broadcast and will forward it out all ports.
B. Every switch in the network receives the broadcast, but only Switch 4 will forward it out port 2.
C. Switches 1, 2, and 4 will receive the broadcast, but only Switch 4 will forward it out port 2.
D. Only Switch 4 will receive the broadcast and will forward it out port 2.
Answer: C
The default behavior of a switch is to propagate broadcast and unknown packets across the network. This behavior results in a large amount of unnecessary traffic crossing the network.
VTP pruning increases bandwidth efficiency by reducing unnecessary flooding of traffic, such as broadcast, multicast, unknown, and flooded unicast packets. VTP pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to access the appropriate network devices. By default, VTP pruning is disabled.
Enabling VTP pruning on a VTP server enables pruning for the entire management domain. VTP pruning takes effect several seconds after it is enabled. By default, VLANs 2 through 1000 or 2 through 1001 are pruning eligible, depending upon the platform. VTP pruning does not prune traffic from VLANs that are pruning ineligible. VLAN 1 is always pruning ineligible and VLAN 1 cannot be removed from a trunk. However, the “VLAN 1 disable on trunk” feature available on Catalyst 4000, 5000, and 6000 family switches enables the pruning of user traffic, but not protocol traffic such as CDP and VTP, for VLAN 1 from a trunk. Use the vtp pruning command to make VLANs pruning eligible on a Cisco IOS-based switch.

Switch( vlan)# vtp pruning

Once pruning is enabled, use the switchport trunk pruning command to make a specific VLAN pruning ineligible.

Switch( config)# interface fastethernet 0/3
Switch(config-if)# switchport trunk pruning vlan remove vlan 5

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
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.

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