broadCast Vs Collizion domain

i need some1 to write me Explanation of Collizon domain & BroadCast domain ... i studyd it but nop i got wt exactly meant by both of teze?
plz :

Sure lets start with collision domains.


Very simply a collision domain is an area on the network where frames have the ablity to collide.


So for example you have 3 computers connected to a hub. You would consider them all to be within the same collision domain because at any time if 2 or more computers tried to transmit data the resulting data would eventually collide as it went out over the wire as hubs do not sort or filter frame traffic. However if you put a switch into play each port on the switch would be in it's own collision domain because switches direct lan traffic to only the intended reciever if known. Routers also create collision domains on each port because local traffic on one port has no chance of colliding with traffic in other networks.

Broadcast domains are even simpler. A broadcast domain is the area on a network in which a broadcast message can reach. Because routers are the only thing that do not forward broadcasts you can easily tell that each network connected to a port on a router defines it's own broadcast domain.

www.cisco.com/E-Learning/prod/curriculum...2/player/player.html

Try that link for a more interactive view.

thanx Navins

if v talking about VLAN ..as 1 of advantagez dat it reduce collizion domain if VLAN implemented... so em thinking if switchz do tiz job then why v consider tiz advntage of VLAN ...
(collizion domain as Mac AND BROADcost domain as ip.. broadcast domn cleard to me but confuzion about colision domn ...>?)
em looking forward for repli...

Nice explanation Nevins.
Truesdq, you might also find the search function on Firewall.cx useful. As well as current answers to your questions, to which you're very welcome, you'll often find that a detailed explanation has already been given, commented on and expanded by the input of many contributors in a past post. You'll find the search link in the black area at the top of every forum pane. Take a look also at the networking articles and knowledgebase, you can get to then via the menus just under the site banner at the top of the page

thanx Navins

if v talking about VLAN ..as 1 of advantagez dat it reduce collizion domain if VLAN implemented... so em thinking if switchz do tiz job then why v consider tiz advntage of VLAN ...
(collizion domain as Mac AND BROADcost domain as ip.. broadcast domn cleard to me but confuzion about colision domn ...>?)
em looking forward for repli...

VLANs like routers create Broadcast domains. Essentially the point of a VLAN is to allow a switch to operate different ports on different networks. You can think of it like this:

You have a 24 port switch.
You also have 15 normal employees and 3 accounting employees.
The normal employees should NOT be able to see the accounting data because it may cause them to be upset about who gets paid how much, therefore you have decided to put them on another network.

You have the option of installing another switch and installing another line connection from your router but this will end up costing you extra money.

You have decided to use a VLAN to create that new equipment with your old equipment LOGICALLY.

To do this instead of installing a new trunk line to a new switch you tell the router that it will be trunking 2 networks over logcially created subinterfaces on the same wire.

Additionally you assign some ports (at least 15) to the normal employees under one subinterface and some ports (at least 3) to the accounting department under the other sub interface. The sub interface on the router now creates 2 broadcast domains for each network... note the only device that creates broadcast domains is still a router.



So in summary using sub interfaces a router can have more the one broadcast domain attached to it in order to suport vlan's and more then one subnetwork on a single interface. The fact remains however the devices that the broadcast domains end at is a router. The only real difference is by use of vlan's broadcast domains can also be seperated by port. The best way to think about it is a vlans broadcast domain is everything including the trunklines and subinterface within that vlan up to the point of a routing interface.

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