interface ethernet 0
 ip address 10.10.10.1 255.255.255.0
 ip nat inside

!--- Defines Ethernet 0 with an IP address and as a NAT inside interface.


interface ethernet 1
 ip address 10.10.20.1 255.255.255.0
 ip nat inside

!--- Defines Ethernet 1 with an IP address and as a NAT inside interface.


interface serial 0
 ip address 172.16.10.64 255.255.255.0
 ip nat outside

!--- Defines serial 0 with an IP address and as a NAT outside interface.


ip nat pool no-overload 172.16.10.1 172.16.10.63 prefix 24
 !

!--- Defines a NAT pool named no-overload with a range of addresses !--- 172.16.10.1 - 172.16.10.63.


ip nat inside source list 7 pool no-overload
 !
 !

!--- Indicates that any packets received on the inside interface that !--- are permitted by access-list 7 has !--- the source address translated to an address out of the !--- NAT pool "no-overload".


access-list 7 permit 10.10.10.0 0.0.0.31
access-list 7 permit 10.10.20.0 0.0.0.31

!--- Access-list 7 permits packets with source addresses ranging from !--- 10.10.10.0 through 10.10.10.31 and 10.10.20.0 through 10.10.20.31.