Switch Communication

Dear Users
i am first time at this forum.thanks for the owner for making so informative forum i have one question about switch please reply me Thanks in advance...

as i red that when pc1 send a packet first time to another pc2 connected with same switch. the switch add mac address and port no of sending computer...but question is this first time with which information a computer try to communicate with another computer....bcz mac address he dont know does it communicate with port????if yes then how it knows which computer is connected to which port.....on the switch

waiting for reply
Thanks

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Comments

Ltat42a

If the switch doesn't know which port PC2 belongs to, it will flood the frame out all ports asking who's mac address this is. When pc2 answers, the switch will add pc2's mac address to the forward/filter table and port number, then send the frames to pc2. If other PC's are connected to the switch, they will drop the frames because their mac address does not match the destination mac address.

hth

aljugan

Dear sir
thanks a lot for reply as you mention in your reply that .....if the switch doesn't know which port pc2 belogngs to it will flood the frame out all ports asking who's mac address this is...........i want to ask that from where pc1 got the mac address of pc2......?? Thanks in advance

SecurityThroughObscurity

PC1 will use ARP.

jdballinger

Aljugan, when PC1 sends the ARP request, which contains the IP address of PC2. If the switch has already learned the MAC of PC2, then the entry exists in the MAC table and the switch is who responds to the ARP request. If however the switch has not received any frames from PC2 and thus doesn't know the MAC, then it will flood out of all ports (except the port it received the request on) a frame that contains an ARP request packet. When PC2 sees this request, and sees that it matches with the IP address in the packet, it will respond with it's MAC address, completing the cycle.

If you are still confused, I recommend either Googling "ARP process" or looking on YouTube for a video (there are some good ones out there.)

aljugan

Dear Sir
Thanks a lot now its clear to me.........first information is used ip address this one i didn't know before....thanks for your kind response.

aljugan

Dear sir
hope you will be fine.i have one another question actually i am living in Iran and here i cant use social media to connect my friends and exchange the ideas.sir i want o ask you that when we talk about layer 2 (switch layer). after this is said mostly that frame is forwarded to physical medium.but we use one another physical medium which is used from computer to Switch.why this physical medium is not discussed anywhere. Thanks

greenerek

aljugan wrote: »

Dear sir
hope you will be fine.i have one another question actually i am living in Iran and here i cant use social media to connect my friends and exchange the ideas.sir i want o ask you that when we talk about layer 2 (switch layer). after this is said mostly that frame is forwarded to physical medium.but we use one another physical medium which is used from computer to Switch.why this physical medium is not discussed anywhere. Thanks

Hello,

I am not sure, what you mean. There is not to much to discuss about layer1.To connect switch with PC you need straight-through cable. To connect similar devices like router to router use crossover(or straight-through with Auto MDIX). The real game starts in layer3

aljugan

Hellow sir
Thanks for your kind reply.let me ask my question in another words...........where ethernet frame is prepared...either on ethernet card it got prepared or on switch.......i repeat my question ....which device prepare the Ethernet frame ......NIC card or swithc..Thanks a lot

jdballinger

It depends on where the data is originating. For instance, if a switch is sending out a layer 2 broadcast (an ARP request perhaps) then it will create the ethernet frame. Generally though what you will deal with will be a host of some sort creating the initial frame, via the NIC. The switch will still interact with the frame since it contains information that the switch needs to forward the traffic, but initial generation would be done on the host.

aljugan

Dear sir thanks for your kind response Lan chapter is finished now i am going to start wan if there will be any confusion i will ask you. sir from which country you are???.
Thanks a lot

jdballinger

I'm from the United States. Good luck on your studies, and remember to never be afraid to ask when you have questions! This forum is filled to the brim with people who want to help each other out, and we really do have some really smart people who can answer your questions.

aljugan

hellow sir hope you will be fine.sir i have one question about wan.sir all the chapter i red just one thing i didnt understand when a internetwork is shown two routers are connected by a z type of line.and shown that here one one network exist as well. what type of this network is which connects two routers by serial connection thanks a lot