NAT & PAT Network Address Translation Port Address Translation

Why use NAT?  Ability to use private addresses internally and still access the Internet RFC1918 addresses are not globally unique  Ability to connect overlapping IP address space  Not a security cure

NAT Characteristics  Converts internal private address to configured public address that is routable  Performed statically or dynamically  Creates state table on connection  Delete state table entry on disconnect  With use of ACLs to prevent routing, can add to security profile, control traffic

NAT Applications  Hardware and software firewalls  Routers  Proxy servers RAS server that is a simple router/firewall

NAT Configuration  NAT(config)#access-list 1 permit  NAT(config)#ip nat pool public netmask  NAT(config)#ip nat inside source list 1 pool public-1  NAT(config)#interface fa 0/0  NAT(config-if)#ip nat inside  NAT(config-if)#interface s 0/0  NAT(config-if)#ip nat outside

NAT  Show IP nat translations Pro Inside global Inside local Outside local Outside global  Show IP nat statistics

PAT  Ip nat pool net  Access-list 1 permit ip  ip nat inside source list 1 pool net-1 overload  Int f0/0 Ip nat inside  Int s0/0 Ip nat outside  NAT#show ip nat translations Pro Inside global Inside local Outside local Outside global Tcp : : : :4806 tcp : : : :4809 tcp : : : :4814 tcp : :

Your NAT configuration  X = the second digit of your loopback IP address  (config)#access-list 1 permit 1x  (config)#ip nat pool public-1 21x x netmask  (config)#ip nat inside source list 1 pool public-1  (config)#interface fa 0/0  (config-if)#ip nat inside  (config-if)#interface s 0/0  (config-if)#ip nat outside

Testing NAT  Extended ping from your loopback to a serial interface of your neighbor  When ping works – Show ip nat translations