Question

Select the default STP timer values from the left, and place them over the corresponding STP timers on the right. Each timer value can be used only once. Not all timer values will be used.

2 seconds

20 seconds

15 seconds

1 second

6 seconds

10 seconds

30 seconds

60 seconds

hello	2 seconds
max age	20 seconds
forward delay	15 seconds

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Accepted Answer

Spanning Tree Protocol (STP) uses three timer values: the hello timer value, the forward_delay timer value, and the max_age timer value. The hello timer value is the time between the sending of bridge protocol data units (BPDUs). Switches send BPDUs to determine the path cost to the root bridge. A switch assumes that it has lost connectivity with a neighbor root bridge or neighbor designated bridge after it misses three BPDUs, which are sent every two seconds by default. Therefore, the STP information is removed from a switch after six seconds pass without the switch receiving a BPDU.

STP information is also removed after a set period of time. The max_age timer value is the maximum length of time before old BPDU information is removed. By default, the max_age timer is set to 20 seconds.
STP interfaces exist in one of five states: blocking, listening, learning, forwarding, or disabled. The forward_delay timer value is the time a port spends in the listening state and learning state. By default, the forward_delay timer is set to 15 seconds.

Switches use the STP timer values on BPDUs that they receive, not on the local STP timer values configured on the switch itself. Therefore, only the timers configured on the root bridge will be used throughout the network. If you want to modify STP timer values, you should change them on the root bridge and the backup root bridge, at a minimum.