Monday 10 June 2019

What is Multicast? How its works?

In this chapter, we’ll see the basics of multicast. 

First, let’s talk about what multicast is… well in simple words we can say answer multicast is sending a message from a single source to selected multiple destinations.

There are three types of traffic that we can choose from for our networks:


Unicast If we want to send a message from one source to one destination, we use unicast.

broadcast If we want to send a message from one source to everyone, we use broadcast.

multicast if we want to send a message from one source to a group of receivers? Then we use multicast.

Why do we want to use multicast instead of unicast or broadcast? 

Multimedia using Unicast 

The application sends one copy of each packet to every client. Used when only a few clients need to access the application. If the message has to be sent to a large group, the same information has to be carried multiple times, even on the same link. Bandwidth usage is proportional to number of users. Routers make individual routing decisions based on each pair of source and destination.

Multimedia traffic using broadcast

The application sends only a copy of each packet using a broadcast. All end hosts need to process even if they don’t want to. Not recommended implantation for applications delivering data, voice, or video to multiple receivers.

Multimedia traffic using multicast

The most efficient solution – in between broadcast and unicast. The server sends one copy of each packet to a special address that represents multiple clients. The server sends out a single data stream to multiple clients.

Advantage of multicast

It saves bandwidth and controls network traffic by forcing the network to replicate packets only when necessary. Reduce network bandwidth consumption and host processing. Control network traffic and reduce server and CPU loads. 

Multicast Components

first, we use a designated range of IP addresses that is used for multicast traffic. We use the class D range for this: to These addresses are only used as destination addresses, but not as source addresses. The source IP address will be the device that is sending the multicast traffic.

we use IGMP ( internet group management protocol ) for hosts to tell the routers when and which multicast traffic they want to receive.

To help the switch figure out where to forward multicast traffic, we can use IGMP Snooping. 

we use a multicast routing protocol: why? we see in the next chapter.
  • DVMRP (Distance Vector Multicast Routing Protocol)
  • MOSPF (Multicast Open Shortest Path First)
  • PIM (Protocol Independent Multicast)
how does multicast work?

step 1- Multicast server application configured with layer 3 address (class- D)
step 2- Multicast application installed on all the hosts.
step 3- Indicate the router that they want to receive multicast traffic for the group (IGMP)
step 4- Multicast routing protocol forward multicast server. (PIM)
step 5- Calculate layer 2 multicast MAC address (IGMP Snooping/ CGMP)

This is basis of multicast, 
Thanks for reading 







Thursday 6 June 2019

Network Address Translation (NAT)

Network address translation

NAT is the method of translation of private IP address into public IP address. In order to communicate with internet we must have registered public IP address.

Address translation was originally developed to solve two problems:
  1. To handle a shortage of IPv4 addresses
  2.  Hide network addressing schemes.

Private address range

There are certain addresses in each class of IP address that are reserved for private networks. These addresses are called private addresses.

Class A             TO
Class B         TO
Class C       TO

Types of NAT :-

Static NAT
Dynamic NAT
Port address Translation (PAT)

Static NAT- one to one mapping done manually for every private IP need on registered IP address (one to one)

Dynamic NAT- one to one mapping done automatically For every private IP needs one registered IP address (one to one)

Port address translation ( Dynamic NAT Overload )- Allows thousands of users connect to the internet using only one real global IP address. Maps many to one by suing different ports. PAT is the real reasons we are haven’t run out of valid IP address on the internet.







What is Virtual Router Redundancy Protocol (VRRP)? How to configure Virtual Router Redundancy Protocol (VRRP)?

 Virtual Router Redundancy Protocol (VRRP) is a gateway redundancy networking protocol used to create a virtual gateway similar to HSRP . VR...