Network Pen Questions

First set:
Basic knowledge of the network to examine

One, the basic part
1, the Chinese full name of the OSI is (International Organization for Standardization),
They are (application layer) presentation layer (Presentation layer) session Layer Transport layer (Transport layer)
The Network Layer Data link layer (physical layer) is the physical layer.

2. Hub Hub works in the (physical) layer of the OSI Reference Model, and the NIC works in the (physical) layer of the OSI Reference model;
The router router works at the (network) layer of the OSI Reference model; switch switch works at the (data link) layer of the OSI Reference Model.

3, the IP address of machine A is 202.96.128.130, 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), please use simple language to explain how it works.
1. First, each host establishes an ARP list in its own ARP buffer (ARP Cache) to represent the correspondence between the IP address and the MAC address.
2. When the source host needs to send a packet to the destination host, it first checks its own ARP list for the MAC address of the IP address.
If so, send the packet directly to the MAC address, or, if not, initiate an ARP request broadcast packet to the local network segment, which is queried for this purpose
The MAC address that the host corresponds to. This ARP Request packet includes the IP address of the source host, the hardware address, and the IP address of the destination host.
3. After all hosts in the network receive this ARP request, the destination IP in the packet is checked for the same as its IP address. If it is not the same, ignore this
If the same, the host first adds the MAC address and IP address of the sending side to its own ARP list if the IP is already present in the ARP table
Information, it overwrites it and sends an ARP response packet to the source host, telling the other person that it is the MAC address it needs to find;
4. After the source host receives this ARP response packet, it adds the IP address and MAC address of the destination host to its own ARP list, and takes advantage of this information
Begins the transfer of data. If the source host has not received an ARP response packet, it indicates that the ARP query failed.
5. DNS refers to the domain Name System. Please describe how it works in simple language.

When a DNS client needs a name that is used in a query program, it queries the DNS server to resolve the name.
Each query message sent by the client includes 3 messages to specify the question the server should answer.
1 specifies the DNS domain name, expressed as a fully qualified domain name (FQDN).
2 Specifies the type of query that can specify resource records by type, or as a specialized type for query operations.
3 The specified category of the DNS domain name.

6. The difference between TCP and UDP
TCP provides connection-oriented, reliable data flow transmission, while UDP provides non-connection-oriented, unreliable data streaming.
Simply put, TCP is focused on data security, while UDP data transfer is fast, but security is generally
7, the role of the gateway.
It provides access to the extranet


Two, Network command
1. What is the role of Ipconfig?
Displays the settings value for the current TCP/IP configuration

2. What is the result of running net share return?
Lists information about shared resources such as ipc$

What are the 3, net use and net user points respectively?
NET user is used by users to manage, add, and remove network users.
NET use for network device management, such as adding disks
4. How to view the current system open service under the command line?
Executing the Net services command at the command line
5. In addition to the above commands, what else, please write the commands you know.
Taskill
Taslist
NET view display computer list
Netstat
Ftp
Telnet

Third, system ports and services
1, turn off the following services, what kind of situation will appear, and please explain your views.
Automatic Updates
cannot be automatically updated

Plug and Play
Disabling causes USB to not be used.
Remote Registry Service
Protect yourself from browsing the Web to modify your registration form
Computer Browser

The service cannot maintain an up-to-date list of computers on the network and provide this list to the requesting program.
2. Ports and the relative service
FTP (21 File transfer FTP service)
Port for Terminal Services is (3389)

23 Port is (TELNET) open default port

25 Port is (e-mail SMTP) Open

109 ports are (POP2) open

1433 port is (SQL Server) Open

Four, network protocol
Icmp:
is an abbreviation for Internet Control message Protocol (Internet controlled messaging protocol).
It is a sub-protocol of the TCP/IP protocol family that is used to pass control messages between IP hosts and routers.
The control message refers to the message that the network is not accessible, whether the host is available, whether the route is available, and so on.
These control messages, while not transmitting user data, play an important role in the delivery of user data.
Tftp:
Trivial file Transfer Protocol, a protocol used in the family of TCP/IP protocols for simple file transfer between client and server
Provides an uncomplicated, inexpensive file transfer service.
HTTP:
HTTP Hypertext Transfer Protocol, an object-oriented protocol belonging to the application layer, is suitable for distributed hypermedia information System because of its simple and fast way.
It was proposed in 1990, after several years of use and development, has been continuously improved and expanded.
　　　
DHCP: Dynamic Host Configuration Protocol, a means of enabling a system to be connected to a network and acquiring the required configuration parameters

Second set:
The Network knowledge examines

One, the blank question.
1, the protocol used to transfer information between the browser and the WWW server is (http).
2, in the Star LAN structure, the device connecting the file server to the workstation is (switch).
3, after the installation of the Linux system, the system automatically created the Administrator account is (root).
4, the unit is divided into a legitimate IP address 202.112.68.40 mask of 255.255.255.248, where the router's outer port and the ISP occupy 2,
If you use 202.112.68.41 and 202.112.68.42, the Mask is 255.255.255.252
Q: 1, how many legitimate IPs are available?
Also available are 202.112.68.44/29, 202.112.68.45/29, 202.112.68.46/29
Q: 2, the use of internal IP address translation, if you use a host to connect the internal and external two networks, please say 2 different network connection method, and to compare?

1) host connected to a piece of network card binding two different subnets address, run the agent software, the internal network will set the gateway to the host.
2) host plug-in 2 network cards, respectively connected inside and outside the network, the host gateway and address conversion role.
1) in the scheme if the network misappropriation host legitimate IP can bypass the host
2) cannot bypass the host.


Q: What internal IPs are reserved on 3,internet for use?
can be used 10.0.0.0 or 172.16 straight 172.31 or 192.168.0 straight 192.168.255

5, how to plan a firewall to isolate internal business servers and some PCs from the Internet?
A demilitarized zone can be built to provide internal service to the intranet through the intra-network router.
Some PCs have access to the Internet via the external network by connecting some of the internal PC computers on the internet,internet.
Set up a router or proxy server between the demilitarized zone and the intranet as a firewall, restricting external access.

6, in China, currently available to choose a large number of users to choose the mode of access, the respective access rate is?
DDN up to 2M

ISDN 64k*2 (2b+d)

Frame Relay up to 2M

X. 64K
[[[DDH (Up to 2M)
ADSL (Asymmetric digital subscriber line, downlink rate from 512kbit/s to 8mbit/s, and upstream rate from 64kbit/s to 640kbit/s)
ISDN (Integrated Services Digital Network maximum speed up to 64Kbps or 128Kbps)]]

7, can the 2 subnets quarantined by the router be a common DHCP server? Can't
8, what command can the user see the native IP address they have applied to? What command can I use to re-request IP from the DHCP server? What command can I use to free up IP?
Ipconfig/all
Ipconfig/release Release IP
Ipconfig/renew Get new IP
The multiplexing technology used by the 8,ADSL is (a)
A. Frequency division multiplexing B. Time Division Multiplexing
C. Code Division Multiple Access D. Space division Multiple addresses

Second, question and answer question.
1, write down the function of the network command below.
Netstat–p (Statistics and Protocol control block information for only the name of the protocol are printed)
Net view (displays a list on a computer in the current domain or on a network)
How to display the Windows service (NET Services) under the command line

2, the role of the bridge.
is a bridge between a local area network and another LAN to establish a connection

3, implemented with one command: Map the remote host C drive to its own F-drive
net use F: \ \ Remote host ip\c$ "password"/user: "username"
5, the firewall port protection refers to?
Refers to the firewall through the port switch settings, to close some non-essential ports, to achieve a certain security protection purposes behavior.

Network Pen Questions