How the STP determinw that which Port should be Root Port,
which port should be Designeted Port , Blocking Port and
Forwarding Port in Layer 2 STP topology........

Hi friends Thanks for posting the answer of above given
questions i agree with all of you that BPDU is the Protocol
that are used to determine this is clear to me..

But I want to Know the Process like Why it Blocked the port
Fa0/1 Insted of Fa0/2

waiting for Answer Posting ....
Thanks in Advance

Answer Posted / jitu

hi
from your question i fell that you want to about process of
stp.
so
as we know that stp is the process in which we avoid the
switchnig loop.this loop is occured due to redudancy that
is alternate path.
this alternate path is given due to if one link get down
then another link get up and data flow remail continue.but
one draw back is there if both the link up then data found
two path and its create loop so to stop this we apply stp
i think you agree witj that ?


ok now the complete process i am going to expalin.


let take a example

switch1
| |
| |
| |
switch2 switch 3
| |
| |
switch4---------switch5
now supose that mac address of switch one is 1201
switch two is 8955
switch three is 1202
switch four is 2101
switch five is 9870

asume that all switch have default priorty value that is
32768
scine switch one has the higest mac addess then it wiil
become root bridge and rember that in root bridge all the
port are in forwarding mode.

Then follow up the connection the port is concetd to the
root bridge switch become root port and root port alway
become
f


follow the conection from switch one two all switch so port
directly conec in taht case port of switch 3 adn switch
four port become root port

no procced further
scine switch 4 and switch 5 port are closest port from
switch 3 and 4 and have the low cost then this port bill
become root port and alswys in forwarding mode

now bridge id come in acount to detrmine the deseignated
and non deseignated port
scine swich 4 have the lowest bid value then its port will
desigeinated and forwardin else switch five port will be in
blocking mode

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