Basics about networking (CCNA) part -2

So now we have made the computing (Networking), we know the cabling technology we use, we know which jack it goes to, you know what device it is connected to, we know the identity of computer (MAC Address also known as physical address) and now we know how these are connected like LAN,WAN,MAN.

Let us see how exactly the two computers will communicate in a Local Area Network, so the LAN is I have two computers which are present in my office connected to each other, let us see how these two computers communicate with each other. So as shown above we have computer A and computer B, so if computer a wants to communicate with computer B inside a small campus, so it should have an addressing style, let us say in my office I have two points each point should have a naming convention, as we have already defined the name of two computers for the whole world. We have to define a nick name to both computers to communicate on LAN, which we can define with a protocol with rule, what is that rule it is called as Addressing style (IP Addressing).

What is an IP address?

Every device connected to the public Internet is assigned a unique number known as an Internet Protocol (IP) address. IP addresses consist of four numbers separated by periods (also called a 'dotted-quad') and look something like 127.0.0.1.

Since these numbers are usually assigned to internet service providers within region-based blocks, an IP address can often be used to identify the region or country from which a computer is connecting to the Internet. An IP address can sometimes be used to show the user's general location.

Because the numbers may be tedious to deal with, an IP address may also be assigned to a Host name, which is sometimes easier to remember. Hostnames may be looked up to find IP addresses, and vice-versa. At one time ISPs issued one IP address to each user. These are called static IP addresses. Because there is a limited number of IP addresses and with increased usage of the internet ISPs now issue IP addresses in a dynamic fashion out of a pool of IP addresses (Using DHCP). These are referred to as dynamic IP addresses. This also limits the ability of the user to host websites, mail servers, ftp servers, etc. In addition to users connecting to the internet, with virtual hosting, a single machine can act like multiple machines (with multiple domain names and IP addresses).

In IP Addressing we have different type of addressing which is called as IPV4 (Version 4), For Ex – 192.168.1.10 it is a IPV4 IP address. This is also called logical address and this would be the name of our computer.

For Ex:-

Computer A has IP Address as 192.168.1.10.

Computer B has IP Address as 192.168.1.11.

Note:- The name for computer A and computer B cannot be same, it should be different as I have shown above. So in a LAN I have defined a name by using a protocol called as IP Addressing. 

What is Mac Address?

It is abbreviated as Media Access Control Address. It is a unique identifier to network interfaces for communication on the physical network segment. The Media Access Control Address is a 48-bit or 64-bit address associated with a network adapter. The MAC Address is a number used by network adapters to uniquely identify them on a LAN. Mac addresses are often considered permanent, but in some circumstances, they can be changed. There are two types of Mac addresses:-

Universally Administered Address

The UAA, or Universally Administered Address, is the most commonly used type of MAC Address. This is the only one which is provided to the product when it is manufactured. The first three octets define the manufacturer, while the second three octets vary and identify the individual adapter. All network adapter manufacturers have their own unique code, called Organizational Unique Identifier (OUI). For Ex: - In MAC address 00-04-DC-c7-46-23, the first three octets are 00-04-DC. This is the OUI for Dell. Other common OUIs include 00-40-96 for Cisco  00:10: DB for Juniper, 00-30-BD for Belkin etc. Most large manufacturers of networking equipment have multiple OUIs.

Locally Administered Address

The LAA, or Locally Administered Address, is an address that changes an adapter’s MAC Address. The LAA is a type of administered MAC address, and it is possible to change the LAA of a network adapter to any address of allowed length.  When the LAA is set, the network adapter uses the LAA as its MAC address. Otherwise, the network adapter uses the UAA as its MAC address.

Mac addresses are useful for security purposes, as they are only rarely changed from the default. IP addresses can change dynamically, especially on networks using DHCP to assign IP addresses, so MAC addresses are often a more reliable way to identify senders and receivers of network traffic.

On wireless network Mac address filtering is more common security measure to prevent unwanted network access. We use Mac address filtering, a wireless router is configured to accept traffic from a certain Mac addresses only. In this way, as white listed devices are assigned new IP addresses through DHCP, they retain their ability to communicate on the network. Any intruder attempting to impersonate a valid user on the network by masquerading with faked ip address will not be able to do so because the computer’s MAC address not match any of those in the white list  This security method is only minimally successful, however, as a determined intruder can fake a MAC address almost as easily as an IP address.

So how does these two computers communicate that is the biggest question?

We have a MAC address, we have a NIC name address (IP Address), after that if you needs to communicate you should need a protocol (set of rules), what should be the rule required to communicate is

ARP (Address Resolution Protocol).

What does ARP do?

It converts the MAC address to IP Address, ARP protocol converts the name (MAC to IP). I.e.:- MAC Address to 192.168.1.10.

Congratulations now we have established a connection between two computers, now how do we go out for transferring the data for which we have one more rule to once again transfer the data which is called as TCP (Transmission Control Protocol),so if we want to transfer the data from computer A to B we use protocol (TCP). How does it travel with a medium called as Packets.

Packets are a medium how the data travels from A source to B destination and vice versa.

Now what are Hosts?

Don’t get confused when some buddy asks about hosts, host is the name given to stand alone computer on a network. So how do u come to know what is the name of your computer :-

Click on start.

Click on run.

Type cmd, click on OK.

Type host name and hit enter.

Name of computer would be shown there on command prompt.

Click next for more.