Home » Cisco » 200-105 » Which tertiary switch can take over?
If primary and secondary root switches with priority 16384 both experience catastrophic losses, which tertiary switch can take over?
A. a switch with priority 20480
B. a switch with priority 8192
C. a switch with priority 4096
D. a switch with priority 12288
Correct Answer: A
Explanation/Reference:
Explanation:
In my opinion the switch with the lowest priority becomes the Root so B seems the correct answer but the consensus is on ANSWER A. Can anyone explain this please. The answer is A because the other priorities are lower than root 16384. STP chooses priority first before mac address, so there can’t be any switches with lower priority than the primary or secondary root switches. Otherwise they would have been the root to begin with.
The priority of the primary (8192) and the secondary (12288) root switches was elected as 16384. As Adelson Lovato mentioned, the primary root switch was elected with 8192, and as you add 4096 to the primary root, that gave you the secondary root switch elected with priority 12288. You then add 4096 + 12288 which = 16384. Switch priority goes up in increments of 4096, as the next backup root switch would be an increment of 4096 which is added to the primary and secondary root switches priority 12288 that experienced catastrophic losses. 4096 + 16384 = 20480. After the initial failures you cannot go down in priority only up in priority.
The correct answer is A because switch 1 and 2 have priority 16384, so because STP election chooses the lower Root ID, the number of tertiary switch should be greater than 16384. In this case the option ia A.
If the root bridge priority was 8192, it will be the primary switch instead tertiary.
awesome answer …
how this 20480 becomes the answer ?
Adelson Lovato is correct.