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How To enable NAT/PAT on your Cisco IOS router
General Configuration
To enable NAT on your IOS powered Cisco router, follow these simple steps.
1.) Identify your outside (public) interface. This interface is usually a serial interface, dialer interface, or another ethernet interface.
2.) Identify your inside (private) interface. This is usually ethernet0/0 or fastethernet0/0.
3.) Specify what IP netblock you want to NAT or NAT all subnets.
4.) Enter the configuration and test.
Example
In this example, we use serial0/0 for the "outside" interface and ethernet0/0 for the "inside" interface. We also NAT every IP subnet from the "inside" interface.
router(config)#
!
! Goto your "outside" interface and tell it how to NAT
interface serial0/0
ip nat outside
exit
!
! Goto your "inside" interface and tell it how to NAT
interface ethernet0/0
ip nat inside
exit
!
! Build an Access-List to tell the router what subnets to block.
access-list 101 permit ip any any
!
! Tell the router to use the new Access-List and to NAT using PAT
ip nat inside source list 101 interface Serial0/0 overload
exit
copy running-config startup-config
Now you are setup to access the Internet with your internal subnets.
1.) Identify your outside (public) interface. This interface is usually a serial interface, dialer interface, or another ethernet interface.
2.) Identify your inside (private) interface. This is usually ethernet0/0 or fastethernet0/0.
3.) Specify what IP netblock you want to NAT or NAT all subnets.
4.) Enter the configuration and test.
Example
In this example, we use serial0/0 for the "outside" interface and ethernet0/0 for the "inside" interface. We also NAT every IP subnet from the "inside" interface.
router(config)#
!
! Goto your "outside" interface and tell it how to NAT
interface serial0/0
ip nat outside
exit
!
! Goto your "inside" interface and tell it how to NAT
interface ethernet0/0
ip nat inside
exit
!
! Build an Access-List to tell the router what subnets to block.
access-list 101 permit ip any any
!
! Tell the router to use the new Access-List and to NAT using PAT
ip nat inside source list 101 interface Serial0/0 overload
exit
copy running-config startup-config
Now you are setup to access the Internet with your internal subnets.