Why don the ProCurve 5400zl products support virtual stacking?
Stacking is primarily a feature for the 24-port and 48-port switches to create a port density comparable to a larger chassis switch. Since the ProCurve 5400zl switch already meets port density needs, it is not necessary to support the single IP address management between multiple 5400zl switches (stacking). You can use ProCurve Manager (PCM) software to manage multiple ProCurve 5400zl switches from a single user interface if this is desired. PCM is available for free; you can download it from: www.hp.com/rnd/software/network_management.