Consider an institutional LAN shown in the figure below that

Consider an institutional LAN shown in the figure below, that is composed of five hosts (A, B, C, D, and E) and two transparent switches (Switch 1 and Switch 2). Assume that five frames are exchanged between the hosts as follows: A sends to B, D sends to E, E sends to C, B sends to A, and C sends to E. Show the detailed learning process and contents of the switch tables of each of the two switches in each step of the process

Solution

When a Host sends frame to a another host connected to the switch , switch broadcast the frame seeking the mac address of destination address. Destined machine responds with its mac address .

here switch tags the mac address with switch interface in its switching table.This is called learning process so when next time a frame is sent switch wont broadcast it. it will directly sends the frame to destination machine.

Here in this case when A sends to B switch 1 will broadcast seeking mac address of destined host , here B responds with its mac address. there fore switch tags the mac address of A & B with interface 1 & 2 respectively.

similarly when D sends to E , switch S2 broadcast and learns the mac address of D & E from Interface 2 & 3 respectively .

Similarly , when E sends to C switch S2 broadcast it and frmae reaches to S1 where interface 3 of switch 2 responds with its MAC address.

tables on S1 and S2 would be

mac address of E would be tagged on interface 4 on switch S1 and interface 3 on switch S2 , mac address of of C would be tagged with interface 3 on switch S1 and interface 1 on switch S2.

When B sends to A , it will be matched in switching table of S2 and be directly forwarded to A as the interface and mac address of A & B already tagged in switching table.

When C sends to E , frmae will egress through interface 4 of switch S1 and ingress in interface 1 of switch S2 and forwarded to E through Interface 3 since the tagging is already there in switching table .

learning process is one time when switch broadcast the frame , once switch tags/learns the mac address to corresponding interface it maintains the table if it is not cleared the mac table or rebooted.

Hope it will help you .

Thanks