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NAT Static

Written by Rene Molenaar on . Posted in Network Services

Scenario:

As one of the network engineers for a small company you are responsible for all network operations. One of the branch offices has a single host PC that needs access to a server located on the internet. You only have private IP addresses for your internal network so you need to configure network address translation (NAT). Since there is only a single host a static NAT will be sufficient.

Goal:

  • IP addresses have been preconfigured as specified in the topology picture.
  • Create a static NAT configuration on router NAT to translate the 192.168.12.1 IP address into the 192.168.23.2 IP address.
  • You are not allowed to translate any port numbers.

IOS:

c3640-jk9s-mz.124-16.bin

Topology:

NAT Static

Video Solution:

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Comments (4)

  • avatar
    rizzas
    2010-12-07 12:50:41

    hello,
    i think i am going to enjoy GNS3. i download NAT Static lab. the routers are not configured. do i need to setup something to load the configuration?

    thanks, rizzas

  • avatar
    ReneMolenaar
    2010-12-07 17:17:11

    Hello rizzas,

    In the attachment there are startup-configs for all routers. The routers should have IP addresses on them. If not you can always copy/paste the config in the terminal session but it should auto-load when you open the topology in GNS3.

    Rene

  • avatar
    tohritz
    2011-11-02 18:30:41

    Hi Rene,

    I was able to follow the lab and understood the nat process, however, I'm curious why the server was able to ping the host or vice versa even if they don't have the routes to each other (e.g., route from server to host).

    when you do show ip route on either server or host, shows no route to each other.

  • avatar
    ReneMolenaar
    2011-11-03 01:13:48

    Hi Rito,

    Good question. If you look at the startup config of the "host" router you can see I disabled "IP Routing". This ensures it doesn't build a routing table and becomes an ordinary host. I also configured a default-gateway on it so it uses the NAT router.

    The server doesn't require a default gateway after NAT translation because it's "talking" with IP address 192.168.23.2 which is on the same LAN.

    Do a "debug ip packet" on the server and send a ping from the host. You'll see the source and destination IP address. Useful for checking NAT...