Analysis of wrong questions
1. Which part of the IP address 205.140.36.68 represents the network number (D)
Reason analysis:
- 205 is between 192 and 223, so it is a class C address;
- The network number of class C address occupies 24 bits;
- So choose D;
2. The reorganization of IP datagram fragments usually occurs in (D)
Reason analysis:
- Fragmentation is completed by routers at the network layer;
- After the destination host receives all the fragments, the process of reassembling and restoring the fragments is called IP datagram reassembly. The IP protocol stipulates that only the final destination host can reorganize fragments ;
3. Which of the following does not belong to the disconnected state of tcp connection? C
reason analysis:
- C option is the state in the TCP connection;
- C is the synchronous sending state, at the end of the active connection;
4. IP address 10.1.8.0/24 and 10.1.9.0/24, which of the following is the correct summary network segment: C
Reason analysis:
- 10.1.8.0/24 ——10.1.0000 1000.0/24
- 10.1.9.0/24 ——10.1.0000 1001.0/24
- Only the first 23 digits of the two are the same, so 10.1.8.0/23
5. The address belonging to the network 112.10.200.0/21 is (A)
Reason analysis:
- 112.10.200.0/21——112.10.1100 1000.0/21
- Then the top 21 is fixed at 112.10.1100 1;
- Therefore, the third part of the range is greater than 200 and less than 207;
- So only A satisfies;
6. The description of the following TCP connection establishment process is correct: C
reason analysis:
- SYN_SENT in A is the status of the active connecting party, that is, the client;
- After receiving the ACK in B, it is the third handshake, the connection has been established, and it is in the ESTAB_LISHED state;
- C is correct;
- D is timeout retransmission, which is one of the very important mechanisms for TCP connections, and the other is the acknowledgement response (ACK) mechanism;
7. The TCP connection establishment process uses a three-way handshake. It is known that the sending sequence number of the third handshake message is 1000, and the confirmation sequence number is 2000. The sending sequence number and confirmation sequence number of the second handshake message are: B
reason analysis:
- Pay attention to the question, what is known is the third time , and what is sought is the second time ;
- The third confirmation serial number = the second serial number+1;
- The third transmission sequence number = the second confirmation sequence number;
8. What message is sent by the application PING: C
Reason analysis:
- PING is a sub-protocol of ICMP in the network layer
- Ping is located at the user level and is generally used to test whether a host is reachable. The program sends an ICMP echo request message to the host and waits for an ICMP echo response to be returned;
9. In the HTTP protocol, if you want to inform that the requested webpage has been permanently redirected to another address, which status code should be returned: A
Reason analysis:
- 301 is a permanent jump;
- Links to the introduction of various status codes
- 302 is temporary;
10. In the Internet, which of the following is not the problem that the IP layer needs to solve: A.
Reason analysis:
- Flow control is at the transport layer;
- Data link layer: error control
- Network layer: routing, addressing, congestion control, segmentation and reorganization
