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Wednesday, 14 November 2018

VTP (VLAN Trunking Protocol) and how VTP works

VTP (VLAN Trunking Protocol):-

VTP stands for VLAN Trunking Protocol. VLAN trunking protocol is a Cisco proprietary protocol and it’s used by Cisco switches to exchange VLAN information. By the help of VTP, we can synchronize VLAN information with switches inside the same VTP domain. For example we can synchronize VLAN id or VLAN name. VTP uses layer 2 frames to manage the addition and deletion and renaming of VLANs from switches in the VTP client mode.
Suppose we have 100 switches. Without VTP, if we want to create a VLAN on each switch, we would have to manually enter commands to create the VLAN only on one switch. That switch can then propagate information about that VLAN to each switch on a network and cause other switches to create that VLAN too. If you want to delete a VLAN, we only need to delete it on one switch and the change is automatically propagated to every other switch inside the same VTP domain.

How VTP works:-

We have three switches and we have created a new VLAN on SW1. SW1 sends a VTP update to SW2 and SW2 sends own VTP update to SW3. Now all three switches have the same VLAN.

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Saturday, 20 October 2018

IPv6 (Internet Protocol Version 6)

IPv6 (Internet Protocol Version 6):-

Internet protocol version 6 (IPv6) is the newest version of the IP protocol. IPv6 is an internet layer protocol. It’s used for identification the system and location of the system on the internet. Internet version 6 (IPv6) developed by the IETF (Internet Engineering Task Force) and it’s developed to the problem of IPv4 addresses exhaustion. The IPv4 provides approximately 4.3 billion addresses and IPv4 uses 32 bit (232) address. If you want to check your IP address. you can search on search engine what is my ip address.
The IPv6 provides approximately 3.4x1038 addresses and IPv6 uses 128 bit (2128) address. IPv6 separated by colon sign and represents in eight groups of four hexadecimal digits. For example 3201:0ac8:1238:0000:8dbc:0380:8855. Internet protocol version 6 was first defined in RFC 1883 and published in December 1995. In December 1998 RFC 1883 replaced with RFC 2460. In July 2017 RFC 2460 replaced with RFC 8200.

IPv6 (Internet Protocol version 6) Features:-

Internet protocol version 6 uses large 128-bit addresses. Its means that for each person on the earth there are 48x1027 addresses.

Internet protocol security (IPSec) is built into IPv6 as part of the protocol. This means that two devices can dynamically create a secure tunnel without user intervention.

The Internet protocol version 6 packet header simple than the IPv4 because the IPv6 header is not protected by checksum. So the router does not need to calculate checksum for every packet.

In Internet protocol version 6 no need to NAT (Network Address Translation) because every devices has a globally unique IPv6 address.

The Internet protocol version 6 devices can automatically configure themselves with an IPv6 address.

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Friday, 12 October 2018

Access control list (ACLs) and types of Access Control List (ACL).

ACL (Access Control List):-

The ACLs stands for Access Control List.  Access Control List (ACL) is a list of permission and used for filter network traffic. Access Control List (ACL) used on network devices with packet filtering capabilities like Router or Firewalls. ACL tells to network devices what types of packets accept or deny. ACL’s are applied on the interfaces to packets leaving or entering.
ACL provides basic level of security for network access and increase network performance because the traffic is limited.

How ACL's Works:-

Suppose a company who has 2000 users and 500 employees. The company server (Server1) holds some important documents. They documents are available only for company employees and users can't access this documents. For denied those document to users access we could configure an Access Control List on router (Router1).  After configured ACL all other traffic going to server will be blocked. Now we can ensure that only authorized user can access documents.

There are two types of ACL’s:-

 Standard Access List
Extended Access List
Named Access List

Standard Access List:-

By Standard Access List we can filter only on the source IP address of packet. These type of access list are not powerful as extend access list, but they are less processor intensive for the router. The standard access list identification number between 1 to 99 or 1300 to 1999. Its blocks the whole network and implements near the destination.

Extend Access List:-

In extend access list we can more precise in our filtering. We can evaluate source and destination IP addresses and source and destination port. The extend access list identification number between 100 to 199 or 2000 to 2699. It’s harder to configure, require more processor intensive as standard access list. Extend access list allows much more granular level of control.

Named Access list:-

Name access list allow standard and extended access to be given names instead of numbers. It provides some features like name is case sensitive and name can’t start with number or space. We can delete individual statement in a named access list.

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Wednesday, 26 September 2018

HTTPS (Hyper Text Transfer Protocol Secure)


The HTTPS stands for Hyper Text Transfer Protocol Secure. HTTPS is secure version of HTTP. By the HTTPS, secure communication establishes between clients andservers. HTTPS uses encryption. The HTTPS uses TCL (Transport Layer Security) or SSL (Secure Socket Layer) protocol for make communication encrypted and HTTPS uses TCP port 443 for encryption.

It mostly used to protect sensitive information like username and password or used for payment transaction on the World Wide Web (www) and also protect e-mail and corporate information systems. HTTPS (Hyper Text Transfer Protocol Secure) is commonly used to create secure channel over the internet. 
By default most of the traffic is unencrypted and hackers easily do sniffing attacks for getting information. The HTTPS usually not used on the entire website in internet because the encryptions slow down the website speed.
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ALSO Read HTTP (Hyper Text Transfer Protocol)

HTTP (Hyper Text Transfer Protocol)


The HTTP stands for Hyper Text Transfer Protocol. HTTP is a client-server protocol that allows requesting web pages from web server for client. HTTP is an applicationlayer protocol widely used on internet. Web servers usually use TCP(Transmission Control Protocol) port 80.
The version of HTTP in common use published in 1997 and defined in RFC 2068 .The HTTP client and web server use request-response method to communicate with each other’s. Client sends the HTTP request and server responding with HTTP responses.

How HTTP works:-

Client mostly using different-different web browsers (like Chrome, Firefox and Internet Explorer etc.). When a user wants to access any web page then it types web page address with http (like
and the browser sends an HTTP request message to the server. Now the server response with the requested web page and the client easily accesses the web page.
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ALSO Read HTTPS (Hyper Text Transfer Protocol Secure)

Wednesday, 5 September 2018

SMTP (Simple Mail Transfer Protocol) Commads, Responses and Mail transfer Phases.

SMTP (Simple Mail Transfer Protocol) uses some commands and the responses to transfer message between an MTA Client and MTA Server.


1.    Hello:-

This command used by the client to identify itself.
For example - user sends own email with HELO.
HELO: (Client mail)

2.    MAIL From:-

This command used by the client to identify the sender of the message.
Example: MAIL From: (Sender mail)

3.    RCPT To:-

This command used for identify the receiver.
Example: RCPT To:

4.    DATA:-

This command is used for send the actual data or actual message.

5.    Quit:-

The Quit command used for terminates the message.

6.    RSET:-

This Command aborts the current mail transaction and the connection is reset.

7.    VRFY:-

This command used for verify the receiver address.
Example: VRFY:

8.    HELP:-

This command asks the receiver to send information about the command sentence argument.
Example: HELP: mail

Example of Responses:-

1.    Positive Condition Reply:-

211- System Status
214- Help
220- Service Ready
221- Service Closing

2.    Transient Negative Completion Reply:-

421- Service NA
450- Mail NA
451- Command Aborted

3.    Permanent Negative Completion Reply:-

500- Syntax Error
554- Transaction Failed

Mail transfer Phases:-

There are three types of phases.

1. Connection Establishment
2. Message Transfer
3. Connection Termination

Connection Establishment:-

Firstly MTA Server send message with code "220: Service Ready" to MTA Client. It means the service is ready and server ready for receiving mail. Then MTA Client reply with HELO message and send email address for identification ( Then MTA server replies with code "250: OK" (Positive Reply).
So the connection established.

Message Transfer:-

In message transfer, client sends “Mail from:” commands to server. Then server replies with code "250: OK". Then client sends other thing (like receiver mail and other) and server reply with code "250: OK".  Now the client sends the actual data (like- complete header and body transformation) and server replies with "250: OK".
So it’s the process of message transfer.

Connection Termination:-

The client will sends a Quit message to server. If the server is ready for Quit connection then server replies with code "221: service closed".
So these are the Mail Transfer Phases.

ALSO Read WHAT IS SMTP (Simple Mail Transfer Protocol)

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