what is the difference between HSRP and VRRP?and between MST and PVST?
VRRP is standard based and can work in a multivendor context
HSRP is Cisco proprietary.
The two protocols provide default gateway redundancy
b) MST and PVST
Per vlan STP executes an STP instance for each L2 vlan that has a port (access or trunk) associated to it.
MST 802.1s standard allows to use up to 16 STP instances to represent 4094 vlans.
so in MST multiple vlans are associated to a single STP instance (each instance is rapid SPT 802.1w)
this provides scalability
Hope to help