Chandu
The native vlan is there to support connectivity to switches that do not support vlan tagging so that if the switch on the other end of the link cannot interpret frames with vlan tags added it can still process the non tagged native vlan packets.
Nowadays most, if not all, switches do understand vlan tagging so it is very rare you need it for it's original purpose and you can in fact on a lot of Cisco switches actually tell the switch to tag the native vlan as well.
Jon
