Version 7.5.1.0 Introduced on the C-Series.
pre-Version 
6.2.1.1
Introduced on the E-Series.
Related 
Commands
max-age – changes the wait time before STP refreshes protocol configuration information.
hello-time – changes the time interval between BPDUs.
hello-time
Set the time interval between generation of the spanning tree bridge protocol data units (BPDUs).
C-Series, E-Series, S-Series, Z-Series, S4810
Syntax
hello-time seconds
To return to the default value, use the no hello-time command.
Parameters
seconds
Enter a number as the time interval between transmission of BPDUs. 
The range is 1 to 10. The default is 2 seconds.
Defaults 2 seconds
Command Modes SPANNING TREE
Command History
Version 8.3.11.1 Introduced on the Z9000.
Version 8.3.7.0 Introduced on the S4810.
Version 7.7.1.0 Introduced on the S-Series.
Version 7.5.1.0 Introduced on the C-Series.
pre-Version 
6.2.1.1
Introduced on the E-Series.
Related 
Commands
forward-delay – changes the wait time before STP transitions to the Forwarding state.
max-age – changes the wait time before STP refreshes protocol configuration information.
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