Cisco 831 - IOS version 12.4-10A - The box has one standalone ethernetIF, and one 4port inside switch.

How is this possible?




interface Ethernet0
 duplex auto
 speed auto
!
interface Ethernet1
 duplex auto
 speed auto
!         
interface Ethernet2
 duplex auto
 speed auto
!         
interface FastEthernet1
 duplex auto
 speed auto
!         
interface FastEthernet2
 duplex auto
 speed auto
!         
interface FastEthernet3
 duplex auto
 speed auto
!         
interface FastEthernet4
 duplex auto
 speed auto

Why is there 3 Ethernet interfaces defined? Ethernet0, Ethernet1 and Ethernet2 - on top of that, the FastEthernet's 1 thru 4.