. . . 7th Lecture - Networking . . .

[k2s]

Today's Topic:

1) Switching & Bridging Logic- How Switches Learn The MAC addresses

2) VLANS

3) Spanning Tree Protocol ( If time permits & on Public Demand)

[Antaraatma]

%<>( %<>( lecture 6 lo kuda ide topics vesinattunnavu..  sCo_^Y sCo_^Y sCo_^Y

[k2s]

[quote author=Antaraatma link=topic=237832.msg2965333#msg2965333 date=1316120886]
%<>( %<>( lecture 6 lo kuda ide topics vesinattunnavu..  sCo_^Y sCo_^Y sCo_^Y
[/quote]that was yesterday & class was cancelled

[robo]

#~` #~`

[k2s]

[quote author=ROBO link=topic=237832.msg2965340#msg2965340 date=1316120940]
#~` #~`
[/quote] CITI_$D#

[Antaraatma]

[quote author=k2s link=topic=237832.msg2965339#msg2965339 date=1316120939]
that was yesterday & class was cancelled
[/quote]ok s%H# s%H#

[krldr871]

~"! ~"! ~"!

[k2s]

Ok Guys I am starting the class:

1st Topic: How Switches Learn The MAC addresses
Assuming MAC-address-table is empty
Consider an example, station A with MAC address 0260.8c01.1111 wants to send traffic to station C with MAC address 0260.8c01.2222. The switch receives this frame and performs several actions, as follows:

[img]http://i51.tinypic.com/2jfb4i.gif[/img]

[k2s]

The frame is received from the physical Ethernet 0 port and stored in temporary buffer space, assuming store and forward frame transmission.
Because the switch does not yet know what interface connects it to the destination station, it will flood the frame through all other ports.
While flooding the frame from station A, the switch notes the source address of the frame, and associatesit with port E0 in a new MAC address table entry.
A MAC address talbe entry is created, which stays in the MAC address table up to the age time.
The learning process continues when each station sends frames to the others.

[k2s]

Note: Remember, when a switch doesn't a destination MAC address in its mac-address-table, it will simple broadcast the frame to all ports asking to respond  back unicastly. When a host receives this frame, if that is for its own, it will respond with a unicast frame back to switch, else simply drops that frame

[k2s]

Here station D with MAC address 0260.8c01.4444 sends traffic to station C with MAC address 0260.8c01.2222. The switch performs several actions, as follows:

[img]http://i54.tinypic.com/1tv993.gif[/img]

[k2s]

The source address, 0260.8c01.4444, is added to the MAC address table.

The destination address from the transmitted frame station C, is compared with entries in the MAC address table.
When the switch or bridge determines that no port-to-MAC address mapping yet exists for this destination, the frame is flooded to all ports other than that on which it arrived.
When station C sends a frame back to station A, the switch can also learn the station C MAC address at port E2.

[k2s]

As long as all stations send data frames within the MAC address table entry lifetime, a complete MAC address table is built. These entries are then used to make intelligent Layer 2 forwarding and filtering decisions.

[robo]

CITI_$D#

[k2s]

In short :

A switch receives a frame with a destination MAC address that is currently not in the MAC table What action does the switch perform?

It duplicates the frame to all Ethernetports, except the port it came from.  To elaborate upon this answer, a switch's MAC table is built not from destination addresses it receives, but by the source MAC addresses. So the frame gets broadcasted throughout the broadcast domain, until the end device with a matching MAC address responds to the broadcast, thus giving the switch a new source address to add to its MAC table.