Hello!
Surprised no one has answered this question:
In HSRP version 1, the values that could be used for standby groups ranged from 0 to 255. With networks having so many vlans nowadays for instance, there may be a need to have more than the possible 256 standby group numbers that version 1 could offer you. HSRP version 2 allows the standby groups to be configured with values from 0 to 4095, so definitely some more options there.
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