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Exam 200-301 All Questions

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Exam 200-301 topic 1 question 184 discussion

Actual exam question from Cisco's 200-301
Question #: 184
Topic #: 1
[All 200-301 Questions]


Refer to the exhibit. Which switch becomes the root bridge?

  • A. S1
  • B. S2
  • C. S3
  • D. S4
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Suggested Answer: B 🗳️

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Ali526
Highly Voted 4 years, 4 months ago
B is correct. The lowest value of priority + MAC.
upvoted 33 times
pianetaperez
4 years, 2 months ago
If all switches in a single spanning tree have the same bridge priority, the switch with the lowest MAC address will become the root bridge.
upvoted 18 times
Jakub2023
3 months ago
You don't see the point that Ali526 made, I guess. If a switch has a lower configured priority of 28672 and a VLAN ID of 1328, then the overall priority value ends up being: 30000. Nothing invalid about it, although it does feel like a trick question...
upvoted 2 times
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WeaGLe
Highly Voted 3 years, 7 months ago
It Should be A. Bridge Priority must be in increments of 4096. Allowed values are: 0 4096 8192 12288 16384 20480 24576 28672 32768 36864 40960 45056 49152 53248 57344 61440 A priority of 30000 is invalid.
upvoted 22 times
[Removed]
1 year, 5 months ago
While this is true, I wouldn't suggest trying to read into it so deeply. The priority is invalid because the 4 highest bits of the BPDU Bridge Priority field are reserved for the priority number, while the remaining 12 are reserved for VLANs, meaning the minimum value by which a priority bit can be set or changed is 4096. The configurations in the question aren't just invalid, they're impossible. A network in this state could not exist - it's physically impossible - and therefore no answer could be correct. So it's obvious we just need to take it at face value, and realize they're just trying to ensure we understand the rules of STP root bridge selection, i.e. Bridge Priority > MAC Address.
upvoted 5 times
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MISS4
3 years, 6 months ago
" When the switch is in PVST+ mode without MAC address reduction enabled, you can enter a bridge priority value between 0-65,535. The VLAN bridge ID priority becomes that value. When the switch is in PVST+ mode with MAC address reduction enabled, you can enter one of 16 bridge priority values: 0, 4096, 8192, 12,288, 16,384, 20,480, 24,576, 28,672, 32,768, 36,864, 40,960, 45,056, 49,152, 53,248, 57,344, or 61,440. " https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4000/8-2glx/configuration/guide/spantree.html Since no mode is specified in the quesion, 30000 seems valid.
upvoted 15 times
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Mzaq34
1 year, 6 months ago
you are right. Answer should be A.
upvoted 2 times
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kyleptt
1 year, 10 months ago
Agreed but... I assume they meant say that the invalid priorities are valid (Not sure ) I am thinking we should use the valid priorities numbers ...........
upvoted 1 times
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MinSun600
Most Recent 2 months, 1 week ago
Selected Answer: B
because the priority of S1 high and even the AA:AA as example of mac address the A first letter so higher than others the first root bridge closer to it is the S2 with lower priority and mac add as letters it's tricky as the other guy said they want us to know resolve the STP rules puzzle
upvoted 1 times
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riteshm42
2 months, 3 weeks ago
Selected Answer: A
A is right. Switch 2 and 3 has invalid priority. Priority should be in multiplication of 4096.. like 32768, 28672
upvoted 1 times
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jojolabubu
5 months ago
Selected Answer: B
The 30000 bridge priority is invalid so it will be rounded to the closest multiple of 4096 which is 28672.
upvoted 2 times
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[Removed]
1 year ago
Selected Answer: B
B is correct
upvoted 1 times
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C0tt0nking
1 year, 1 month ago
Selected Answer: C
CC is lower than BB. Both switches have the lowest priority of 30000. So, with that choose the lowest mac (in lexicographic order) = CC
upvoted 2 times
7d040c6
9 months, 1 week ago
Hex CC = 204 Hex BB = 187 BB is lower. Answer is B.
upvoted 1 times
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Iidear
1 year, 3 months ago
Selected Answer: B
B is correct. lowest priority >>> mac >>>> interface
upvoted 2 times
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NewJeans
1 year, 6 months ago
Selected Answer: B
Just accept whatever specified in the question. Don't dig into it. The question says the priority is set to 30000 even if it can't be. Lower priority gets first.
upvoted 5 times
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[Removed]
1 year, 7 months ago
Selected Answer: B
STP is a golf game. Lowest score wins. gg good day Go Dodgers
upvoted 2 times
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bryanyepez92
1 year, 8 months ago
Selected Answer: A
Allowed values are: 0 4096 8192 12288 16384 20480 24576 28672 32768 36864 40960 45056 49152 53248 57344 61440
upvoted 2 times
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melmiosis
2 years, 6 months ago
so the priority is looked at first right... so its between S3 and S2. then the lower MAC is chosen which is S3 cz all Cs rather than Bs. What im i missing?
upvoted 2 times
Sutokuto
2 years, 4 months ago
C is more than B
upvoted 2 times
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ZUMY
2 years, 11 months ago
B is the answer Lowest values are selected ( Priority + MAC )
upvoted 1 times
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onikafei
3 years, 3 months ago
Bridge priority is in the least value: 30000 narrows it down to 2 ports Bb or cc Bb is lowest
upvoted 1 times
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Samir_123
3 years, 3 months ago
Selected Answer: B
correct
upvoted 2 times
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Hodicek
3 years, 5 months ago
LOWEST PRISORITY IS THE SAME 30000 BETWEEN 2 ROUTERS, SO IT WILL CHOOSE THE LOWEST MAC ADDR. WHICH IS B
upvoted 3 times
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Community vote distribution
A (35%)
C (25%)
B (20%)
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