I found how to:
put the following command under the interface:
"switchport priority default 3"
interface FastEthernet2
switchport priority default 3
end
router#sh inter fast 2 switchport
Name: Fa2
Switchport: Enabled
Administrative Mode: static access
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: Disabled
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Trunking VLANs Enabled: ALL
Trunking VLANs Active: none
Protected: false
Priority for untagged frames: 3
Override vlan tag priority: FALSE
Voice VLAN: none
Appliance trust: none
router#
Diego