You want STP to behave similar to RSTP.
Which three configuration settings under the [edit protocols stp] hierarchy on an EX Series switch
allow this? (Choose three.)
A.
max-age
B.
bridge-priority
C.
edge
D.
forwarding-delay
E.
hello-time
Explanation:
According to Ex switches shows max-age, bridge-priority, forwarding delay and Hello time… so it could be one or the other…
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In order for STP to behave like RSTP we need to make sure that the reconvergence time is as close to 6 seconds as possible.
RSTP convergence formula is below;
RSTP = 3 BPDUs i.e. 3 x 2 seconds (for each BPDU), which is 6 seconds.
STP = 2 x forwarding-delay + Max Age = 2 x 20sec + 20 sec = 50 seconds
As you can see that none of the above formulae involve changing the Bridge priority. The Bridge Priority remains same in both RSTP and STP, hence we can rule it out for the above question. This leaves only three valid choices i.e.;
1- Max-age => Default is 20 seconds with a range of (6-40 seconds)
2- Forwarding-Delay => Default is 15 seconds with a range of (4-30 seconds)
3- Hello Time => Default is 2 seconds with a range of (1-10 seconds)
Even after changing all the three parameters, STP can’t match the RSTP reconvergence time because RSTP is distributed model whereas STP is centralized.
Hope that helps
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