L2 VPN Fr, ATM, Ethernet, Vpls
By IMS Asia (https://www. Imsasia. Com)
Questions and Answers
- 1.
A 16-port switch running spanning-tree can have a maximum of how many root ports.
- A.
1
- B.
2
- C.
5
- D.
16
Correct Answer
A. 1Explanation
A 16-port switch running spanning-tree can have a maximum of 1 root port because in a spanning-tree protocol, there can only be one root bridge in a network. The root bridge is the bridge with the lowest bridge ID and all other switches in the network will have a single root port that connects them to the root bridge. Therefore, regardless of the number of ports on the switch, there can only be one root port.Rate this question:
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- 2.
Which of the following is not a method for differentiating between logical layer-2 connections across a shared physical media?
- A.
Ethernet VLAN's
- B.
ATM VPI/VCI
- C.
TCP/IP Port number
- D.
Frame-relay DLCI
Correct Answer
C. TCP/IP Port numberExplanation
The TCP/IP Port number is not a method for differentiating between logical layer-2 connections across a shared physical media. Layer-2 connections are typically differentiated using methods such as Ethernet VLAN's, ATM VPI/VCI, and Frame-relay DLCI. TCP/IP Port numbers are used at the layer-4 (transport layer) of the TCP/IP protocol stack to differentiate between different applications or services running on a device.Rate this question:
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- 3.
Why is the spanning-tree protocol used in a network?
- A.
To prevent routing loops in networks with redundant routed paths
- B.
To segment a network into separate collision domains
- C.
To prevent routing loops in networks with redundant switched paths
- D.
To allow bundling of multiple physical links into one logical connection
Correct Answer
C. To prevent routing loops in networks with redundant switched pathsExplanation
The spanning-tree protocol is used in a network to prevent routing loops in networks with redundant switched paths. This protocol helps to create a loop-free logical topology by selecting a root bridge and blocking certain redundant paths. By doing so, it ensures that packets are not endlessly forwarded in a loop, which can cause network congestion and instability. Instead, it establishes a single active path between network devices, improving network efficiency and reliability.Rate this question:
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- 4.
A disadvantage of spanning-tree is that the path chosen is not necessarily the optimal one.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Spanning-tree is a network protocol used to prevent loops in Ethernet networks. However, one disadvantage of spanning-tree is that it does not always choose the optimal path for data transmission. Instead, it selects a path that avoids loops but may not be the most efficient or shortest path. This can result in suboptimal network performance and slower data transmission times. Therefore, the statement that the path chosen by spanning-tree is not necessarily the optimal one is true.Rate this question:
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- 5.
Spanning tree protocol calculates the path cost based on what?
- A.
Bridge Priority
- B.
Link Bandwidth
- C.
Link Utilisation
- D.
Hop Count
Correct Answer
B. Link BandwidthExplanation
The Spanning Tree Protocol calculates the path cost based on the link bandwidth. This means that it considers the capacity or speed of the links when determining the best path for data transmission. By taking into account the link bandwidth, the protocol aims to ensure efficient and optimal utilization of the network resources. It prioritizes paths with higher link bandwidth, as they can handle more traffic and provide faster data transmission.Rate this question:
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- 6.
Multiple VPLS services can be provisioned over the same set of provider MPLS tunnels.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Multiple VPLS services can be provisioned over the same set of provider MPLS tunnels. This means that a single set of MPLS tunnels can be used to support multiple VPLS services, allowing for efficient use of network resources. This can be achieved by using different Virtual Private LAN Service (VPLS) instances, which are isolated from each other and can be configured to provide separate Layer 2 connectivity for different customers or applications. By utilizing the same set of provider MPLS tunnels, organizations can simplify their network architecture and reduce costs.Rate this question:
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- 7.
Poor performance, collisions and connectivity issues on an ethernet link can often be due to what?
- A.
Misconfigured link speed
- B.
Duplex mismatch
- C.
A loose ethernet cable
- D.
The incorrect VLAN being configured
Correct Answer
B. Duplex mismatchExplanation
Duplex mismatch refers to a situation where two devices connected by an ethernet link have different settings for their duplex mode. This can lead to poor performance, collisions, and connectivity issues because one device may be transmitting data while the other is receiving, causing data to be lost or corrupted. It is a common problem that occurs when one device is set to full duplex mode while the other is set to half duplex mode.Rate this question:
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- 8.
Which of the following will result in a duplex mismatch on an ethernet link?
- A.
Port A configured for 100m, Full Duplex. Port B configured for 10m, Full Duplex
- B.
Port A configured for 100m, Full Duplex. Port B configured for Auto-detect
- C.
Port A configured for Auto-detect, Port B configured for Auto-detect
- D.
Port A configured for 10m, Half-duplex, port B configured for 100m, half-duplex
Correct Answer
B. Port A configured for 100m, Full Duplex. Port B configured for Auto-detectExplanation
If Port A is configured for 100m, Full Duplex and Port B is configured for Auto-detect, it will result in a duplex mismatch on the ethernet link. This is because Port A is set to operate at a specific speed and in full duplex mode, while Port B is set to automatically detect the speed and duplex mode. This mismatch in configuration can lead to communication issues and performance degradation on the link.Rate this question:
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- 9.
Which of the following Routers would be elected as the root-bridge?
- A.
R1 - Priority 32768, MAC Address 4A:40:AA:08:85:61
- B.
R2 - Priority 16384, MAC Address 4A:40:AA:01:22:38
- C.
R3 - Priority 32768, MAC Address 4A:40:AA:00:15:82
- D.
R4 - Priority 16384, MAC Address 4A:40:AA:35:81:76
Correct Answer
C. R3 - Priority 32768, MAC Address 4A:40:AA:00:15:82Explanation
The root-bridge in a network is elected based on the Bridge Priority value. In this case, both R1 and R3 have the same priority of 32768. However, the tiebreaker is the MAC Address, and R3 has the lowest MAC Address among all the routers. Therefore, R3 would be elected as the root-bridge.Rate this question:
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- 10.
Which timer affects how often the Spanning Tree Root Bridge will send configuration BPDU's?
- A.
Hold Timer
- B.
STP Timer
- C.
Keepalive Timer
- D.
Hello Timer
Correct Answer
D. Hello TimerExplanation
The Hello Timer affects how often the Spanning Tree Root Bridge will send configuration BPDU's. The Hello Timer is a timer used in the Spanning Tree Protocol (STP) to determine how often the Root Bridge should send Hello BPDUs to other switches in the network. These Hello BPDUs are used to establish and maintain the network topology and elect the Root Bridge. By sending Hello BPDUs at regular intervals, the Root Bridge ensures that all switches in the network are aware of its presence and can make necessary adjustments to the network topology if needed.Rate this question:
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- 11.
Which of the following ethernet specifications defines link aggregation?
- A.
802.3z
- B.
802.11a
- C.
802.3ad
- D.
802.3ah
Correct Answer
C. 802.3adExplanation
The correct answer is 802.3ad. This specification, also known as Link Aggregation Control Protocol (LACP), defines the method for combining multiple physical network links into a single logical link. It allows for increased bandwidth, redundancy, and load balancing across the aggregated links, improving network performance and reliability.Rate this question:
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- 12.
What is a key difference between VPLS and L2VPN services?
- A.
VPLS requires the provider supplies the CE equipment, L2VPN's do not
- B.
L2VPN's must use OSPF as their signalling protocol, VPLS uses BGP
- C.
VPLS functions in a point-to-multipoint mode, while L2VPN's function only as point-to-point
- D.
L2VPN's require the use of MPLS in the provider network, while VPLS does not
Correct Answer
C. VPLS functions in a point-to-multipoint mode, while L2VPN's function only as point-to-pointExplanation
VPLS (Virtual Private LAN Service) operates in a point-to-multipoint mode, which means it allows multiple sites to be connected together in a single bridged domain. On the other hand, L2VPN (Layer 2 Virtual Private Network) functions only as point-to-point, meaning it can only establish a connection between two sites. This key difference makes VPLS more suitable for scenarios where multiple sites need to communicate with each other as if they were on the same LAN, while L2VPN is more appropriate for connecting two specific sites together.Rate this question:
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- 13.
Which of the following operations MUST a PE device support when functioning in a VPLS network? (select the one that is not)
- A.
MAC Learning
- B.
Flooding packets sent to an unknown MAC address.
- C.
Proxy-ARP
- D.
Packet Forwarding
Correct Answer
C. Proxy-ARPExplanation
A PE device in a VPLS network must support MAC Learning, flooding packets sent to an unknown MAC address, and packet forwarding. Proxy-ARP is not a required operation for a PE device in a VPLS network.Rate this question:
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- 14.
You are required to provide fully meshed connectivity between 5 customer sites. How many L2VPN's are required to achieve this?
- A.
1
- B.
5
- C.
10
- D.
20
Correct Answer
C. 10Explanation
To achieve fully meshed connectivity between 5 customer sites, each site needs to be connected to every other site. In a fully meshed network, each site has a direct connection to every other site, resulting in a total of (n * (n-1))/2 connections, where n is the number of sites. In this case, with 5 customer sites, the calculation would be (5 * (5-1))/2 = 10 connections. Therefore, 10 L2VPN's are required to achieve fully meshed connectivity between the 5 customer sites.Rate this question:
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- 15.
One of the improvements of Rapid Spanning tree is that it not only chooses a valid path between nodes, it also chooses the optimal path?
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Rapid Spanning Tree Protocol (RSTP) is an improvement over the original Spanning Tree Protocol (STP) which aims to provide faster convergence in network topologies. While RSTP does choose a valid path between nodes, it does not necessarily choose the optimal path. The main goal of RSTP is to eliminate unnecessary blocking of ports and reduce the convergence time, rather than finding the absolute shortest path. Therefore, the statement that RSTP chooses the optimal path is false.Rate this question:
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- 16.
Which of the following statements is false?
- A.
VPLS is a point-to-point service
- B.
VPLS is a bridged service
- C.
VPLS provides VPN connectivity to CE devices
- D.
VPLS will allow for broadcast communication between CE devices
Correct Answer
A. VPLS is a point-to-point serviceExplanation
VPLS is not a point-to-point service. It is a bridged service that provides VPN connectivity to CE devices. VPLS allows for broadcast communication between CE devices, which means that multiple devices can communicate with each other simultaneously.Rate this question:
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- 17.
Which of the following statements are true?
- A.
Frames should be switched based on destination MAC address
- B.
Frames should be sent only to the PE attached to the destination when possible
- C.
Frames should be flooded as little as possible
- D.
All of the above are true
Correct Answer
D. All of the above are trueExplanation
All of the given statements are true. Frames should be switched based on the destination MAC address to ensure that they reach the intended recipient. Frames should also be sent only to the Provider Edge (PE) attached to the destination when possible, as this helps in efficient routing and reduces unnecessary network traffic. Finally, frames should be flooded as little as possible to minimize network congestion and optimize the use of network resources. Therefore, all of the statements are correct.Rate this question:
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- 18.
Which of the following are true? (choose two)
- A.
Kompella style L2VPN's use BGP as the signalling protocol
- B.
Kompella style L2VPN's use LDP as the signalling protocol
- C.
Martini style L2VPN's use BGP as the signalling protocol
- D.
Martini style L2VPN's use LDP as the signalling protocol
Correct Answer(s)
A. Kompella style L2VPN's use BGP as the signalling protocol
D. Martini style L2VPN's use LDP as the signalling protocolExplanation
Kompella style L2VPN's use BGP as the signalling protocol because it is a Layer 3 VPN technology that uses BGP to distribute VPN routes between the PE routers. On the other hand, Martini style L2VPN's use LDP as the signalling protocol because it is a Layer 2 VPN technology that uses LDP to establish the pseudowires between the PE routers.Rate this question:
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- 19.
VPLS supports which types of physical connection?
- A.
Ethernet, ATM and Serial connections
- B.
Ethernet and ATM connections only
- C.
Ethernet and Serial connections only
- D.
Ethernet Connections only
Correct Answer
D. Ethernet Connections onlyExplanation
VPLS, or Virtual Private LAN Service, supports only Ethernet connections. This means that it can be used to connect Ethernet-based devices or networks together, providing a virtual LAN over a wide area network. VPLS does not support ATM or Serial connections, limiting its compatibility to Ethernet-based systems only.Rate this question:
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- 20.
How many MPLS LSP's are required in each direction between PE1 and PE2 to support 100 VPLS domains across this network?
- A.
1
- B.
100
- C.
200
- D.
9900
Correct Answer
A. 1Explanation
The correct answer is 1 because MPLS LSP's (Label Switched Paths) are used to establish connections between Provider Edge (PE) routers in a VPLS (Virtual Private LAN Service) network. In this case, only one MPLS LSP is required in each direction between PE1 and PE2 to support 100 VPLS domains across the network. This means that a single path can be used to carry traffic for all 100 VPLS domains, making it more efficient and reducing the number of LSP's needed.Rate this question:
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- 21.
Which of the following MPLS signaled LSP's will support VPLS transport?
- A.
RSVP Signalled LSP's Only
- B.
LDP Signalled LSP's Only
- C.
Both RSVP and LDP signalled LSP's
- D.
MPLS LSP's are not used for VPLS transport
Correct Answer
C. Both RSVP and LDP signalled LSP'sExplanation
Both RSVP and LDP signalled LSP's will support VPLS transport. RSVP (Resource Reservation Protocol) and LDP (Label Distribution Protocol) are both used in MPLS (Multiprotocol Label Switching) networks to establish and maintain Label Switched Paths (LSP's). VPLS (Virtual Private LAN Service) is a technology that allows the extension of a LAN over a wide area network using MPLS. Therefore, both RSVP and LDP signalled LSP's can be used to support VPLS transport.Rate this question:
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- 22.
Which priority if configured would be elected as the root bridge?
- A.
R1 - Priority 4096
- B.
R2 - Priority 8192
- C.
R3 - Priority 16384
- D.
R4 - Priority 32768
Correct Answer
D. R4 - Priority 32768Explanation
The priority value determines the likelihood of a switch becoming the root bridge in a spanning tree network. The switch with the lowest priority value will be elected as the root bridge. In this case, R4 has the highest priority value of 32768, which means it has the lowest priority compared to the other switches. Therefore, R4 would be elected as the root bridge.Rate this question:
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Mar 20, 2023Quiz Edited by
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Mar 10, 2011Quiz Created by
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