I have a Windows PC connected to a VLAN ( cisco catalyst 3500 ) switch . The switch has also a DHCP server connected to it. Now when i enable the ethernet interface connected to the VLAN switch ( access mode ) , it takes a long time to get an address from the server . The reason being the switch is dropping the initial DHCP packets sent from the windows PC. The debug messages at in the switch indicate " Line protocol on Interface GigabitEthernet0/7, changed state to down " and after 2 or 3 seconds "Line protocol on Interface GigabitEthernet0/7, changed state to up " and hence when the protocol is down , the packets are getting dropped . only after the interface comes up completely at the switch side the Windows PC gets the address. Can some one please explain why does the line protocol flips its state(up/down ).This problem is not found if i use a LINUX PC as my client.