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spanning-tree dynamic MAC deletion ?


hello guys

can anyone please interpret this sentence please : i mean which command(s) will do this requirement and for which purpose(s) 

"spanning-tree must immediately delete dynamically learned MAC address entries on a        per-port basis upon receiving a topology change"



9 Replies 9

Jon Marshall
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There is no command, this is a part of the spanning tree process ie. if there is a topology change then switch mac addresses must be flushed because they could be pointing to a non existent path after the recovergence. 



Ok so one command or process should make this process you told
can you say which process ? at least one command should exist to becomes switch run this process......
arbitrary process will NOT started.......

Jon Marshall
Hall of Fame Community Legend Hall of Fame Community Legend
Hall of Fame Community Legend


It is not an arbitrary process it is part of how STP works ie. a topology change will start the process. 



so if this is part of process which i know
why should be mentioned in Question ??????
for example sending BPDU , Proposal, ACK and so many other things might be happened during STP process
choosing root bridge , choosing Best path , selective which port should be gone to FW which Designated which one BLK
i am not satisfy
my query is usual events which has been done in process Never should be asked
anywhere it was asked in question
as in question mentioned MUST be deleted either specific mode for spanning-tree must specified or ....
i agree with you while TCN happened MAC have to omitted and replace
but why this should be asked if it is a normal and parts of process
certainly there is other imagination and expect something which i do not know from responder ....
this was parts of task in question ....

Has itoccurred to you that the task/home work question might be incorrect? As jon mentioned. This mechanism is integrated into spanning tree for obvious reasons.

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Thanks Sir
but it was question from one the highest level exam
no it isnt incorrect and also not home work there are several task one of them is that....

i think i figure it out what Question exactly means 

let me i dig into question 

before this task 

asked to ensure that switch run SPT mode which maintain separate SPT instance for each Vlan  

so as i sure this procedure will be occurred during all SPT process so i think this task should insist on previous task which is mentioned above : 

i think designer was thinking about spanning-tree mode rapid-pvst 

i am not sure really what does mean by this task ( not sure whether this is a informational sentence or have to do something special)

too much eager to find it out !!!!!!!!

just one imagination can comes into mind which is just in rapid pvst we have immediately deletion of MAC address due to TCN so in others (RSTP,MST,legacy STP...) we Do not have immediately 

they will be done but not quickly as a question mentioned !!!!

just this i think can be logical 



as question mentioned int should occurs rapidly 

"Rapid PVST+—This spanning-tree mode is the same as PVST+ except that is uses a rapid convergence based on the IEEE 802.1w standard. To provide rapid convergence, the Rapid PVST+ immediately deletes dynamically learned MAC address entries on a per-port basis upon receiving a topology change. By contrast, PVST+ uses a short aging time for dynamically learned MAC address entries"

Do even know how it works on MST? does MST TC delete mac address-table immediatly? Thanks

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