I am doing a Lab for school with a CCNP kit I bought from Amazon.com. I have a Catalyst 2950 switch and 2 Catalyst 3750 with ver 12.2 IOS. I am doing Lab 2.3.2.3 (Configuring Rapid PVST+, PortFast and BPDU Guard) in the Scaling Networks Lab manual. I am using the 2950 as Switch 1. When I get to the trunking config I get an error that says I can not configure trunk because it is encapsulated AUTO. What do I need to do to disable this? Or can I? These are used switches but I deleted the vlan.dat I was not looking at the screen and was just typing the commands for the lab and so it did it on F1/0/1 and i didn't notice until I got to F1/0/3 and it did it again. Here is the error I get? I was not in Cisco when these switches were taught so I do not know all the commands for these old switches. Can anyone help?
t1/0/1, changed state to up
S1(config-if)#switchport mode trunk
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.
S1(config-if)#switchport trunk native vlan 99
S1(config-if)#int f1/0/3
*Mar 1 00:16:04.765: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up
S1(config-if)#no sh
S1(config-if)#sw
S1(config-if)#switchport
*Mar 1 00:16:12.315: %LINK-3-UPDOWN: Interface FastEthernet1/0/3, changed state to up
*Mar 1 00:16:13.321: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0/3, changed state to up
S1(config-if)#switchport mod
S1(config-if)#switchport mode tr
Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.
S1(config-if)#
