1. Three steps to configure NAT
     a. define local address pool (access-l 1 10.0.0.1 0.0.0.255)
     b. define inside and outside interface
     c. ip nat inside source list 1 <outside interface> [overload]
global address: recognized by the world
local address: locally know address
inside or outside: where the IP is specified

2. Configure DHCP:
    ip dhcp pool <name>
        network 172.16.1.0 255.255.255.0
        default router
        dns-server
        domain-name

3. IP helper-address <single IP or broadcast IP>
    no ip forward-protocol udp <number>      to block unwanted services
    put the ip helper-address command on the interface the same as the client

4. IP unnumbered for serial link to save IP