CCNA Lab Video Tutorial 5 – Internet Connections with NAT and PAT

Back>
In this tutorial, we will learn how to configure Internet connections with NAT and PAT.

In project 1, we will configure static NAT on a Router.

The project setup includes two 2620XM Routers with Module WIC-2T installed (Router A and Router B).

Router A’s interface serial0/0 are connected with Router B’s interface serial0/0 via a serial DCE cable (don’t forget to set clock rate for both Routers). Router A have a loopback interface 0, which can be created with command:

RouterA#config terminal

RouterA(config)#int loopback 0

In project 2, we will configure NAT overload/PAT on a Router. The project2's setup is the same as project1, except we have 2 loopback interface loopback0 and loopback1.

Configure static NAT:

To specify the global interface, go to the interface configuration mode and issue command,

RouterA(config-if)#ip nat outside

To specify the local interface, go to the interface configuration mode and issue command,

RouterA(config-if)#ip nat inside

To establish static translation between an inside local address and an inside global address, issue command,

RouteA(config)#ip nat inside source static LOCAL_ADDRESS GLOBAL_ADDESS

Example:

RouteA(config)#ip nat inside source static 172.16.1.1 10.0.0.1

Configure NAT overload:

To specify the global interface, go to the interface configuration mode and issue command,

RouterA(config-if)#ip nat outside

To specify the local interface, go to the interface configuration mode and issue command,

RouterA(config-if)#ip nat inside

To define a pool of global addresses that would be employed in the translation,

Router(config)#ip nat pool POOLNAME START_IP END_IP netmask NETMASK

example:

Router(config)#ip nat pool fastpool 20.0.0.1 20.0.0.10 netmask 255.255.255.0

To associate the pool and the local range in a dynamic NAT translation command,

Router(config)#ip nat inside source list LISTNUMBER pool POOLNAME overload

example:

Router(config)#ip nat inside source list 1 pool fastpool overload

If you have only one global address which can be employed in the translation.

To associate the interface and the local range in a dynamic NAT translation command,

Router(config)#ip nat inside source list LISTNUMBER interface INTERFACE overload

example:

Router(config)#ip nat inside source list 1 interface s 0/0 overload

To define the range of local addresses permitted to participate in the translation using an access-list.

Router(config)#access-list LISTNAME permit LOCAL_ADDRESS NETMASK

Example:

Router(config)#access-list 1 permit 192.168.0.0 0.0.255.255

Debug nat configuration

RouteA#debug ip nat

RouteA#show ip nat translations

Configure default routing

To send all traffic out of serial interface 0/0, issue command,

RouterB(config)#ip route 0.0.0.0 0.0.0.0 s 0/0

Advanced ping

RouteA#ping

Protocol [ip]:

Target IP address: 192.168.1.2

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: loopback0

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.2, timeout is 2 seconds:

Packet sent with a source address of 172.16.1.1

NAT: s=172.16.1.1->10.0.0.1, d=192.168.1.2[0]

NAT*: s=192.168.1.2, d=10.0.0.1->172.16.1.1[0]!