Hi, you have it right, the purpose of trunking is to allow you to extend vlans where you cannot physically install another switch for those vlans for various reasons. For example ideialy you want to have one unique vlan per department so you setup one 48port access switch for users in department-X but cannot do so for department-Y being in same location , here you you can then use trunk from a VTP server switch and a VTP client switc and pass department-Y vlan onto that switch thus having both departments in same switch but different vlans.. here it is assumed there are SVI layer 3 interfaces configured for each vlan if both VLANS need to communicate one another.
On the other hand cascading is simply interconnecting the two switches to be managed using swith cluster techology and no neccesarity need to implement trunking and have it manage through one ip address and mamagement vlan.
Rgds
Jorge
rate any helpful post if it helps!
Jorge Rodriguez
