About the description of IGMP Snooping working mechanism, which of the following statement is true?

• A.The Layer 2 switch establishes and maintains the PIM routing table at Layer 2 by continuously monitoring IGMP messages
• B.If the host sends an IGMP leave message, the switch will add the host to the corresponding multicast table
• C.If a host sends an IGMP host report message, the switch will delete the multicast entry corresponding to the host
• D.When IGMP Snooping is not running, multicast messages will be broadcast on the layer 2. After IGMP Snooping is running, the messages will no longer be broadcast on the layer 2, but will be multicast on the layer 2.

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The following is part of the output information of the router RTB. Which of the following regarding the description of the output information is false?

• A.The multicast address to join is 255.1.1.2
• B.The last host sending the Report message is 225.1.1.2
• C.The number of dynamically joined multicast groups on the interface is 1
• D.The display igmp group command is used to view the IGMP multicast information, including the multicast group information dynamically joined through the member report and the multicast group information statically joined through the command line

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Which of the following descriptions about multicast routing is correct? (Multiple choice)

• A.Multicast routing protocols are divided into intra-domain multicast routing protocols and inter-domain multicast routing protocols
• B.Multicast routing forms a unidirectional loopless data transmission path from the data source to multiple receivers, that is, the multicast distribution tree
• C.Multicast routing protocol is used to establish and maintain multicast routing, and forward multicast data packets correctly and efficiently
• D.Multicast routing protocol including IGMP protocol

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What are the benefits of OSPF area division? (Multiple choice)

• A.It can reduce the size of LSDB and thus reduce the consumption of router memory
• B.A large number of LSA flooding is restricted to a single area
• C.LSA can also be reduced with the division of areas, reducing the consumption of router CPU
• D.Routers in an area can understand the topology details outside their area

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RSTP converges faster than STP. Why? (Multiple choice)

• A.If a designated port in the network fails, the optimal Alternate port in the network will become the designated port and enter the Forwarding state
• B.If a root port in the network fails, the optimal Alternate port in the network will become the root port and enter the Forwarding state
• C.The concept of edge ports is introduced in RSTP. Edge ports do not participate in RSTP operations and can be directly transferred from Disable to Forwarding state.
• D.In RSTP, after a port is elected as a designated port, it will first enter the Discarding state, and then quickly enter the Forwarding state through the Proposal/Agreement mechanism

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