Hi everybody
i'm study ccnp switch and was confused about diameter of the STP 802.1d topology.
Many people explain, that a value of diameter equal seven obtained from the formula:
Max Age value = End-to-End BPDU Propagation Delay + Message Age Overestimate
End-to-end BPDU propagation delay
= ((lost_msg + 1) x hello) + ((BPDU_Delay x (dia – 1))
= ((3 + 1) x hello) + ((1 x (dia – 1))
= 4 x hello + dia – 1
= 4 x 2 + 6
= 14 sec
Message age overestimate
= (dia – 1) x overestimate_per_bridge
= dia – 1
= 6
Max Age = end-to-end_bpdu_propagation_delay + message_age
If I right understood, value of dia equal seven, but it is constant and doesn't change when Configuration BPDU is propagated by the root bridge, or not?
If value of die is change, how root bridge will understand that the network contain more seven switch?
Value of bpdu_delay in the calculation message_age_overestimate will be increased on each switch? when Configuration BPDU travel across from root bridge to sw10 (see pic)?
Assume, we have the follow scheme:
What happens if we leave the timer unchanged? i.e., STP will not converge?
thanks
