Which two statements are true about RSTP? (Choose two.)
A.
By default, RSTP uses a separate TCN BPDU when interoperating with 802.1D switches.
B.
By default, RSTP does not use a separate TCN BPDU when interoperating with 802.1D switches.
C.
If a designated port receives an inferior BPDU, it immediately triggers a reconfiguration.
D.
By default, RSTP uses the topology change TC flag.
E.
If a port receives a superior BPDU, it immediately replies with its own information, and no
reconfiguration is triggered.
The RSTP does not have a separate topology change notification (TCN) BPDU. It uses the
topology change (TC) flag to show the topology changes.
Reference. http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2950/software/release/12-
1_9_ea1/configuration/guide/scg/swmstp.html
However, for interoperability with IEEE 802.1D switches, the RSTP switch processes and generates TCN BPDUs.
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html
For me, the correct anwser is “C” and “D”.
In the link below, you can understand why “C” is correct: http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html#anc9
I think A&D.
Looking at the
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html
mentioned above.
It states “RSTP no longer uses the specific TCN BPDU, unless a legacy bridge needs to be notified”. This short statement confirms A and D.
If A is true then B is false.
E would be true if you replace word “superior” with “inferior”. Otherwise it is false. (according to the link above).
C is also false as the reply to inferior BPDU causes immediate reconfiguration.
See example in the “Accepts Inferior BPDUs” section.