Wednesday, October 31, 2012

[Useful Notes] Broadcast Domain and Collision Domain

1. In switch every port has own a collision domain because switches direct traffic to only correct port.
2. Collision domain broken up by Bridges,Switches and routers
3. Every end device would be plugged to switch port would be 1 collision domain.
4. Broadcast domain depends on how you segmented a network.
5. 1 Hub = 5 Hosts There is only one collision domain. because hub has 1 collision domain and 1 broadcast     domain
6. Collisions are resolved using CSMA/CD (Collision Detection) For retransmit.
7. Mostly collision found on Wifi Network also known as wireless network. (and also in Ethernet Hub environment)
8. Modern wired network uses a network switch to eliminate collisions
9. Separating VLANs divides broadcast domain as well.

Router Benefits

  • Routers by default breakup broadcast domain and it is helps to connect to WAN (Wide-Area-Network),
  • Routers are using something called a serial interface for WAN Connection (V.35 physical interface on a cisco router)

Why we need to breakup broadcast domain?

Breaking up a broadcast domain is very important because now you have to send a "Network Broadcast" to a another host on a network, Some how you have sent the network broadcast to the host in other words every hosts in a network read and process the particular network broadcast message. 

  • Routers are not only breaking up the broadcast domain but also collision domain as well. 

2 Main advantages of using a router

  • They don't forward broadcast domain by default. 
  • They can filter the network based on Layer 3 (We will talk about Layer functions and OSI layers later)

4 Functions of a Router

  1. Packet Switching - Router also defined as "layer 3 Switches". use for logical addressing that's why we called as packet switching.
  2. Packet Filtering and Internetworking - Router also packet filtering to using access list.when two or more routers in a networks together use logical addressing  (IP -IPV4 Or IPV6 ) What is called Internetwork
  3. Path Selection - Routers are using a Routing table (map of the internetwork) to make path selections and forward packets to remote network. 
( I just gave you 3 on the above list but in the 2nd option you'l lsee packet filtering and internetworking, i just combined two options as one)

Maybe You have a Question Like This - How much broadcast needs to a network? 

Actually this is question when i asked in forums when i'm newbie still i'm newbie- I'm taking CCENT so this blog is very helpful to provide the useful notes for your cert exams indeed. so this is the answer,

Always keep in mind - Broadcast domains on how you segmented a network.. 

Tuesday, October 30, 2012

Network Segmentation?

What is a HUB?

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HUB (Layer 1 of OSI Model)  is a device which helps you to connect a LAN (Local -Area- Network) and it's very inexpensive mostly uses in Home networks and troubleshooting perhaps using in some small offices because of budget summary. Hub is provides 10mbps speed and it has 1 Collision domain and 1 Broadcast domain, Called as "Multi Repeater" too.

A normal Ethernet Hub

This is a Dual Speed Hub We will talk about this later