The default interface command erases all commands on the particular interface places the interface in a default state which includes no shutting the interface.  Below is the configuration of an interface before and after running the default interface command.

Sales2#show run interface fastEthernet 1/0
Building configuration…

Current configuration : 128 bytes
!
interface FastEthernet1/0
description Dev Lab
ip address 192.168.3.34 255.255.255.0
shutdown
duplex auto
speed auto
end

Sales2(config)#default interface fastEthernet 1/0
Building configuration…

Interface FastEthernet1/0 set to default configuration

Sales2(config)#do show run interface f 1/0
Building configuration…

Current configuration : 83 bytes
!
interface FastEthernet1/0
no ip address
shutdown
duplex auto
speed auto
end