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| Question ID 18608 | Which two statements about RSTP and MSTP BPDUs are true? (Choose two.)
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| Option A | MSTP switches can detect boundary ports when they receive RSTP version 2 BPDUs.
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| Option B | MSTP switches can detect boundary ports when they receive RSTP version 1 BPDUs.
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| Option C | RSTP switches can process MSTP version 3 BPDUs.
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| Option D | When all boundary switches are running RSTP, MST sends only version 0 configuration BPDUs.
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| Correct Answer | A,C |
Explanation Explanation: A switch running both MSTP and RSTP supports a built-in protocol migration mechanism that enables it to interoperate with legacy 802.1D switches. If this switch receives a legacy 802.1D configuration BPDU (a BPDU with the protocol version set to 0), it sends only 802.1D BPDUs on that port. An MST switch can also detect that a port is at the boundary of a region when it receives a legacy BPDU, an MST BPDU (version 3) associated with a different region, or an RST BPDU (version 2). Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2950/software/release/12- 1_9_ea1/configuration/guide/scg/swmstp.html
| Question ID 18609 | Refer to the exhibit.
All switches have default bridge priorities, and originate BPDUs with MAC addresses as
indicated. The numbers shown are STP link metrics.
After STP converges, you discover that traffic from switch SWG toward switch SWD takes
a less optimal path. What can you do to optimize the STP tree in this switched network?
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| Option A | Change the priority of switch SWA to a lower value than the default value.
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| Option B | Change the priority of switch SWB to a higher value than the default value.
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| Option C | Change the priority of switch SWG to a higher value than the default value.
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| Option D | Change the priority of switch SWD to a lower value than the default value.
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| Correct Answer | D |
Explanation Explanation: In this topology, we see that all port paths and priorities are the same, so the lowest MAC address will be used to determine the best STP path. From SWG, SWE will be chosen as the next switch in the path because it has a lower MAC address than SWF. From SWE, traffic will go to SWC because it has a lower MAC address, and then to SWD, instead of going from SWE directly to SWD. If we lower the priority of SWD (lower means better with STP) then traffic will be sent directly to SWD.