TCP/IP interview questions

I haven't touched the basic knowledge for a long time. It took me more than two hours to finish the two sets of questions. I have limited personal knowledge. If you find any mistakes, please specify-

First set:

Test basic network knowledge

Date: 2008/3/3

Name: amxking

I. Basic Components

1. The full name of OSI is (International Standardization Organization ),
They are (Application Layer) presentation layer (presentation layer) Session Layer (Session Layer) Transport Layer (Transport Layer)
Network Layer (Network Layer) data link layer (Physical Layer )).

2. The Hub hub works on the (physical) layer of the OSI reference model, and the NIC works on the (physical) layer of the OSI reference model;
The router works on the (network) layer of the OSI reference model, and the switch works on the (Data Link) layer of the OSI reference model.

3. If the IP address of machine A is 202.96.128.130 and the subnet mask is 255.255.255.128, the network number of the IP address is (202.96.128 ),
The host number is (130 ).

4. The Chinese meaning of ARP is (Address Resolution Protocol). Use a simple language to describe how ARP works.

1. First, each host creates an ARP list in its ARP buffer (ARP cache) to indicate the correspondence between the IP address and the MAC address.

2. When the source host needs to send a packet to the target host, it first checks whether the MAC address corresponding to this IP address exists in its ARP list,
If yes, the packet is directly sent to this MAC address. If no, a broadcast packet for the ARP request is sent to the subnet segment to query this purpose.
The MAC address of the host. This ARP request packet includes the IP address of the source host, the hardware address, and the IP address of the target host.

3. When all hosts in the network receive this ARP request, they will check whether the destination IP address in the packet is consistent with their own IP address. Ignore this if they are different.
If the IP address is the same, the host first adds the MAC address and IP address of the sender to its ARP list. If the IP address already exists in the ARP table
And then sends an ARP response packet to the source host, telling the target host that it is the MAC address to be searched;

4. After the source host receives the ARP response packet, it adds the IP address and MAC address of the target host to its ARP list and uses this information.
Start data transmission. If the source host has not received the ARP response packet, ARP query fails.

5. DNS refers to the domain name system ). Describe how it works in a simple language.

 
When the DNS client needs to query the name used in the program, it will query the DNS server to resolve the name.
Each query message sent by the client includes three pieces of information to specify the question to be answered by the server.

1. The specified DNS domain name is a fully qualified domain name (FQDN ).

2. The specified Query type. It can specify resource records based on the type or be a special type of query operation.

3. The specified category of the DNS domain name.

 

6. Differences Between TCP and UDP

TCP provides connection-oriented and reliable data stream transmission, while UDP provides non-connection-oriented and unreliable data stream transmission.
In short, TCP focuses on data security, while UDP data transmission is faster, but the security is average.

7. Functions of the gateway.
It can be used to access the Internet.
 
 

2. Network commands

1. What is the role of ipconfig?

Display the current TCP/IP Settings

2. What is the result returned by running net share?

List information related to shared resources, such as IPC $

3. What are net use and net user respectively?

. Net user is used for user management, adding, and deleting network users.
Net use is used for network device management, such as adding a disk

4. How can I view the services opened by the current system under the command line?

Run the Net Services command in the command line.

5. In addition to the preceding commands, write the commands you know.

Taskill
Taslist
. Net View
Netstat
FTP
Telnet

Iii. System ports and services

1. Disable the following services and describe the situation.

Automatic Updates

Cannot be updated automatically

Plug and Play

If this option is disabled, USB cannot be used.

Remote Registry Service

Prevent modifying your registry by browsing the Web Page

Computer Browser

 
You cannot use this service to maintain the latest list of computers on the network and the programs that provide this list to the request.

2. Ports and services

FTP (21 File Transfer FTP service)

The port number of Terminal Services is (3389)

Port 23 is the default port opened by Telnet.

Port 25 is open (E-mail SMTP)

Port 109 is open (pop2)

Port 1433 is open (SQL Server)

Iv. network protocols

ICMP:
Internet Control Message Protocol (Internet Control Message Protocol.
It is a sub-Protocol of the TCP/IP protocol family. It is used to transmit control messages between IP hosts and routers.
A message control refers to a message of the network itself, such as network connectivity, host accessibility, and routing availability.
Although these control messages do not transmit user data, they play an important role in transferring user data.

TFTP:
Trivial File Transfer Protocol is a protocol used in the TCP/IP protocol family to transmit simple files between the client and the server.
Provides File Transfer services that are not complex and costly.

HTTP:
HTTP Hypertext Transfer Protocol (Hypertext Transfer Protocol) is an object-oriented protocol at the application layer. It is applicable to distributed hypermedia information systems due to its simplicity and speed,
It proposed in 1990 that, after several years of use and development, it has been continuously improved and expanded.
　　　
DHCP: A Dynamic Host Configuration Protocol that allows the system to connect to the network and obtain the required configuration parameters.

Second set:

Network knowledge test

Date: 2008/3/3

Name: amxking

1. Fill in blank questions.

1. The protocol used to transmit information between the browser and the WWW server is HTTP ).

2. In a Star LAN, the device connecting the file server to the workstation is (switch ).

3. After the Linux system is installed, the Administrator account automatically created by the system is (Root ).

4. The mask of the valid IP address 202.112.68.40 is 255.255.255.255.248. The vro's external port and ISP occupy two of them,
If 202.112.68.41 and 202.112.68.42 are used, the mask is 255.255.255.255.252.

Q: 1. What are the valid IP addresses available for use?

Available also include 202.112.68.44/29,202.112 .68.45/29,202.112 .68.46/29

Q: 2. Use an internal IP address for address translation. If you use a host to connect the two networks inside and outside, tell the different network connection methods in 2 and compare them?

 
1) The host is bound to two different subnet addresses with a nic, runs the agent software, and points the gateway settings to the host in the internal network.
2) The host inserts two NICs to connect to the Intranet and Internet respectively, and the host performs gateway and address conversion.

1) scheme. If the Intranet steals the valid IP address of the host, attackers can bypass the host.
2) The host cannot be bypassed.

 

Q: 3. What internal IP addresses are retained on the internet for use?

You can use 10.0.0.0 or 172.16 to 172.31 or 192.168.0 to 192.168.255.

5. How do I plan a firewall to isolate internal business servers and some PCs from the Internet?

You can build an internal business server to provide internal services through an intranet router.
Some PCs connect to the Internet through Internet routes, and some PCs in the Internet are restricted to access the Internet.
Set a vro or proxy server as a firewall between the non-military zone and the Intranet to restrict external access.
 

6. In China, which access methods can be selected by a large user and their respective access rates are available?

DDN up to 2 m

ISDN 64 K * 2 (2B + D)

Frame Relay up to 2 m

X.25 64 K

[[DDH (maximum 2 m)

ADSL (Asymmetric Digital user line, downlink speed from 512 kbit/s to 8 Mbit/s, and uplink speed from 64 kbit/s to 640 kbit/s)

ISDN (up to 64 kbps or 128 Kbps for integrated business digital networks)]

7. Can two subnets isolated by routers share one DHCP server? (No)

8. What command does the user use to view the local IP address they have applied? What command can I use to apply for an IP address from the DHCP server? What command can be used to release IP addresses?

Ipconfig/all
Ipconfig/release IP Address
Ipconfig/Renew get new IP

8. The multiplexing technology used by ADSL is ()

A. Frequency Division Multiplexing B. time division multiplexing
C. Code Division Multiple Access D. Space Division Multiple Access

2. Q &.

1. Write the following network commands.

Netstat-P (only the statistical numbers and Protocol control block information of the protocol with the given name are printed)

Net view (display the list of computers on the current domain or network)

How to Display Windows Services under the command line)

2. Functions of the bridge.

Is a bridge between a LAN and another LAN.

 

3. Use a command to map the remote host C disk to its own f disk.

Net use F: // Remote Host IP/C $ "password"/User: "User Name"

5. What is firewall port protection?

Firewall port switch is used to disable some non-essential ports to achieve certain security protection.