Cisco router - SLIP for ETHERSLIP serial connection

! ----- SLIP protocol on Async port
 interface Async1
!--- The async interface that corresponds to the AUX port.
!--- Use the show line command to determine which async interface corresponds
!--- to the AUX port.
  ip address 192.168.10.1 255.255.255.252
 !--- The IP address on the AUX ports of both routers are in the same subnet.
  encapsulation slip
 !--- Set SLIP as the encapsulation.
  async default routing
 !--- This allows routing protocols on the link.
  async mode dedicated
 !
 no ip classless
 !--- The default route points to the Async1 (AUX port) interface.
 logging buffered
 !
 line aux 0
 !--- Line configuration for the AUX port.
  modem InOut
  transport input all
 !--- This allows all protocols to use the line.
  speed 38400
 !--- Set the line speed.
  flowcontrol hardware
 !
! Outside interface
int f0
 ip address 10.4.19.75 255.255.252.0
 ip nat outside
!
!--- NAT for inside SLIP interface
access list 1 permit 192.168.10.0 0.0.0.3
ip nat inside source list 1 interface f0 overload
!--- Finally a default route !
ip route 0.0.0.0 0.0.0.0 10.4.16.1
 end