CSE(646-205)
单选题How does a switch respond when it receives a message?（）A It reads the Layer-5 information and sends the message directly to the intended computer.B It reads the Media Access Control (MAC) address and broadcasts the message to all the computers that are
题目
It reads the Layer-5 information and sends the message directly to the intended computer.
It reads the Media Access Control (MAC) address and broadcasts the message to all the computers that are connected to the switch.
It reads the Media Access Control (MAC) address and sends the message directly to the intended computer.
It reads the Layer-5 information and broadcasts the message to all the computers that are connected to the switch.
相似问题和答案
第1题：
A. It performs a label pop operation and an IP lookup.
B. It performs a label swap operation and an IP lookup.
C. It sends an error message toward the egress router.
D. It sends an error message toward the ingress router.
第2题：
A. an open message with the E bit set
B. an update message with the E bit set
C. an open message with an end-of-RIB marker
D. an update message with an end-of-RIB marker
第3题：
Regarding DHCP (dynamic host configuration protocol), which two of the following choices below are true? (Select two answer choices)
A. The DHCP Discover message uses FF-FF-FF-FF-FF as the Layer 2 destination address.
B. The DHCP Discover message uses UDP as the transport layer protocol.
C. The DHCP Discover message uses a special Layer 2 multicast address as the destination address.
D. The DHCP Discover message uses TCP as the transport layer protocol.
E. The DHCP Discover message does not use a Layer 2 destination address.
F. The DHCP Discover message does not require a transport layer protocol.
A,B 解析：Explanation:
DHCP uses UDP as its transport protocol. DHCP messages from a client to a server are sent to the DHCP server port (UDP port 67), and DHCP messages from a server to a client are sent to the DHCP client port (UDP port 68).The client broadcasts a DHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER message may include options that suggest values for the network address and lease duration. BOOTP relay agents may pass the message on to DHCP servers not on the same physical subnet.
Each server may respond with a DHCPOFFER message that includes an available network address in the "ipaddr" field (and other configuration parameters in DHCP options). Servers need not reserve the offered network address, although the protocol will work more efficiently if the server avoids allocating the offered network address to another client. The server unicasts the DHCPOFFER message to the client (using the DHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to a broadcast address (preferably 255.255.255.255) on the client's subnet.
Incorrect Answers:
C. DHCP messages are broadcast to the "all hosts" address. IP multicast addresses are not used.
D. UDP is used, not TCP.
E. Since DHCP is used so that a client can obtain an IP address, a layer two destination address must be used, as the layer 3 IP address does not yet exist on the client for the return traffic.
F. DHCP, along with nearly every other type of traffic, requires the use of a transport layer protocol.
第4题：
A router receives a packet from a neighbor with an MPLS shim header value of 0.What does the router do with this packet?（）
- A、It performs a label pop operation and an IP lookup.
- B、It performs a label swap operation and an IP lookup.
- C、It sends an error message toward the egress router.
- D、It sends an error message toward the ingress router.
正确答案:A
第5题：
A.Routes traffic down alternative paths and connects the local-area network (LAN) to the wide- area network (WAN)
B.Reads Media Access Control (MAC) addresses to forward messages to the correct location and connects the local-area network (LAN) to the wide-area network (WAN)
C.Stores data on the network and connects the local-area network (LAN) to the wide-area network (WAN)
D.Broadcasts data to all devices that are connected to it across the local-area network (LAN) and wide-area network (WAN)
第6题：
A. It tears down the BGP session.
B. It sends a restart message to the peer.
C. It marks all routes from that peer as stale.
D. It sends a BGP refresh message to the peer
第7题：
In information theory, "information" is regarded as knowledge which reduces or removes(71) about the occurrence of a specific event from a given set of possible events. The concept "event" is to be understood as used in the theory of probability. For instance, an event may be the occurrence of a(72) character or word in a given message or in a given position of a message.In communication theory, channel is defined as that part of a communication system that connects the message source with the message sink. An encoder may be inserted between the message source and the input to the channel, and a(73) between the output of the channel and the message sink. Generally, these two units are not considered as being parts of the channel. In certain cases, however, they may be considered as pans of the message source and message sink,(74) In information theory(75) to Shannon, the channel can be characterized by the set of conditional probabilities of occurrence of all the messages received at the message sink when a given message emanates from the message source.
A．uncertainty
B．unreliability
C．randomness
D．inconsistency
第8题：
Communication is not merely a matter of a speaker forming a thought in language and sending it as spoken message through space, or as a written message on paper, to a listener or reader who listens to or reads it.()
第9题：
A. The frame is dropped.
B. The frame is addressed with a broadcast MAC address and sent out all ports.
C. The frame is sent out all ports except the receiving port.
D. An ARP request is sent out all ports except the receiving port.
E. A destination unreachable message is sent back to the source address.
F. None of the above.
第10题：
What keywords do you need to the access-list to provide to the logging message like source address and source mac address？（）
- A、Log
- B、Log-input
- C、Log-output
- D、Logging
正确答案:B