In reply to AL_verif:
When we have an unpacked array as randc , its not the values in the whole array that would be unique . Rather the value for a particular index would be unique till all iterations are reached .
array1[0] is 'h2 , so if you randomize pkt() you would see unique values ( non 'h2 ) for index 0 for next 6 iterations ( i.e till you call randomize() 7 times ) .
During 8th call to randomize() is the earliest you would see array1[0] as 'h2 again !!