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Sunday, July 18, 2021

Network | NIC card | Topology | Protocol | IP address | Network configuration | resolve.conf | /etc/hosts

1.What is Network?
Combination of two more computers connected together to share their resources each other by means of communication like cable is called Network.
2. What is Networking?
It is a connection between two or more computers to communicate with each other.
3.what are the basic requirements for networking?
(a)NIC (Network Interface Card or controller)
(b)Media (nothing but cables)  (c) Topology   (d)Protocol   (e)IP Addresses
4. Explain about NIC card?
A Network Interface Card or controller is hardware component that connects a computer to a computer network. Each NIC card will be having MAC (Media Access Controller) address to avoid conflicts between same NIC adapters. In Linux these NIC adapter is represented by the word "eth" . 

For example if two NIC cards are there in a system then it will be denoted as "eho","eth1", .....etc.,
5.What is media?
Media is nothing but cable to connect two or systems. Example : RJ 45, CAT 5 and CAT 6, ....etc.,
6. What is topology?
Topology is a design in which the computers in network will be connected to each other. Example for topologies are Bus, Ring, Star, Mesh, Tree topologies.
7.What is protocol?
A Network Protocol defines rules and conventions for communication between the network devices.

Protocols are generally use packet switching techniques to send and receive messages in the form of packets.
Example for protocols are TCP/IP (Transmission Control Protocol and Internet Protocol), UPD (User Datagram Protocol) and HTTP (Hyper Text Transfer Protocol), ....etc.,
8.What are the differences between TCP/IP and UDP protocols?
TCP/IP
UDP
Transmission Control Protocol
User Datagram Protocol
It is connection oriented
It is connection less
Reliable
Non-Reliable
TCP Acknowledgement will be sent / received
No Acknowledgement
Slow communication
Fast communication
Protocol No. for TCP is 6
Protocol No. for UDP is 17
HTTP, FTP, SMTP, ....etc., uses TCP
DNS, DHCP, ....etc., uses UDP
9.What is an IP address?
Every Computer will be assigned an IP address to identify each one to communicate in the network.
address sub components are Classes of an IP address, Subnet masks and Gateway.
Classes of IP address :
The IP addresses are further divided into classes. The classes are A, B, C, D, E and the ranges are given
The IP
below.

Class  A      0.0.0.0    127.255.255.255    255.0.0.0           /8

Class  B      128.0.0.0  191.255.255.255  255.255.0.0       /16

Class  C     192.0.0.0   223.255.255.255  255.255.255.0   /24

Class  D    224.0.0.0    239.255.255.255

Class  E    240.0.0.0    255.255.255.255

10.What is loopback address?
A special IP number (127.0.0.1) is designated for the software loopback interface of a machine.
127.0.0.0 and 127.255.255.255 is also reserved for loopback and is used for internal testing on local machines

11. What are important configuration files in network configuration?
# cat /etc/sysconfig/network

(This file keeps the information about the hostname assigned to the system and if we want to change the hostname permanently, we need to change the hostname in this file)
# cat /etc/sysconfig/network-scripts/ 

(This directory keeps the configuration of network devices connected to the system. Examples are ifcfg-eht0, ifcfg-eth1, ifcfg-eth2, .....etc.,) 

# cat /etc/hosts 

(This file is responsible for resolving hostname into IP address locally. ie., local DNS if DNS server is not available) 

# cat /etc/resolve.conf

(This file keeps the address of the DNS server to which the clients will be accessing to  resolve IP address to hostname and hostname to IP address)

How many types of NIC cards available?
(a)  eth0    (1st NIC card)
(b)  eth1    (2nd NIC card)
(c)  br0 (Bridge -----> used for communication from physical to virtual)
(d)  lo    (loopback device name and IP address is 127.0.0.1)
 

# ifconfig  (to see all the NIC devices connected to the system)
 

12.How many types of cable connections available?
 

(i)    Cross cable   (to connect two systems directly)
(ii)    Straight cable    (to connect more systems with the help of switch)
# ethtool <device name>    (to check the network cable is connected or not)
# miitool <device name>    (It is also used to check the network cable but it will not supports    RHEL - 7and only supports RHEL - 6 and it also works on physical system only not on    virtual system)

13.In how many ways we can configure the network? 

There are two ways to configure the network.
(a) Static Network.
(b) Dynamic Network.
Static Network :In this way we assign the IP address and hostname manually. Once we configure the IP address, it will not change.
Dynamic Network :
In this way we assign the IP address and hostname dynamically. This means the IP address will change
at every boot.



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