To configure an ISDN connection between our Office router and
the ISP's router, and configure static Network Address Translation
on the Office router.
Scenario:
Our small company has recently been assigned the network number
206.222.222.0 by ARIN. Previously the company was using a private IP
address on the internal network. Now that the company is going to be
connected to the Internet, we need to either go to each and every
workstation and configure it with a new IP address, or to use some
kind of IP address translation at the router. For security reasons
our company does not want the computers to be directly on the
Internet, using real IP addresses. Since our company only has a
limited number of computers, we have decided to use static network
address translation. It is our job to configure the ISDN connection
and implement the address translation.
Notes:
Lab Tasks:
Cable the lab as shown in the diagram.
Check to make sure that the correct Cisco IOS is loaded on the
Office router. It should support network address translation.
Preferably IOS version 12.0.5T or later.
The next task is to set up the routers and ISDN connection as in
previous labs:
Configure IGRP routing with the AS# 123. Ensure that no routing
updates will be sent out of interface BRI 0.
Configure the enable password to be cisco.
Configure the correct IP addresses on each of the routers.
Configure the correct ISDN switch type. (National ISDN-1)
Configure the correct usernames and passwords of the router to
be dialed.
Configure the dialer list to permit IP traffic.
Set up the correct static or default routes.
Set up the correct SPIDs on each of the routers.
Make sure that the encapsulation type is PPP.
For security reasons, our Internet service provider has
requested that we configure the authentication type to CHAP.
Configure the correct timeout values, and dialer map addresses.
Don't forget the
no shutdown
command on the interfaces.
Before configuring network address translation on the Office
router, test your configurations by pinging the other router. This
way you are insuring that your basic configuration is correct
before changing it.
The first step in configuring static network address translation
is to establish a static translation between one of the inside
local addresses (internal private network number) and one of the
inside global addresses (one of our real IP addresses). Enter the
global configuration prompt on the Office router and enter the
following commands:
If we needed a static translation for workstation 10.30.30.5,
how would we enter the configuration information into the router?
Next we need to specify which interface is on the inside of the
network. NAT needs to know this information so that it can
translate addresses correctly. For our Office router, this will be
the ethernet 0 or fast ethernet 0/0 port. Use the following
commands for this configuration.
Now we need to specify which interface is on the outside of our
network. Generally it will be the interface that is connected to the
Internet. For our router it is the interface connected to the ISP
router, or the BRI 0 interface.
Now save your new configuration, and retest your connection to
insure that you are still communicating across the ISDN line.
Finally, we need to verify that NAT is operating correctly on our
Office router. Enter the following commands and answer the questions
associated with each command.
Office#show ip nat translations
What information did the router respond with?
Office#show ip nat statistics
What information did the router respond with?
Record the number of Hits
and the number of Misses
Office#show ip nat translations verbose
What information did the router respond with?
Record Create and
the Use
From a workstation on the inside network ping an address on the
outside. For us, ping the workstation on the network off of the ISP
router.
Were you successful?
Office#show ip nat translations verbose
What additional information did the router respond with?
Record Create and the
Use
Office#show ip nat statistics
What information did the router respond with?
Record the number of Hits
and the number of Misses
From the ISP router, ping 206.222.222.2 (which is a statically
assigned global address for the workstation 10.30.30.2 on our internal
network)
Were you successful?
Explain why you got that result. (Hint: Check the ISP's routing
table)
Since we are on a stub network and the internal IP addresses
are hidden from the rest of the Internet, we need to add a static
route to that network on the ISP router. Now add a static route to the
network 206.222.222.0/24 to the ISP router.
What is the command to enter a static route?
Try to ping the IP address 206.222.222.2 again from the ISP
router.
Were you successful this time?
Why did our stub Office router not share information about network
206.222.222.0 with the ISP router?
What would happen if we incorrectly applied the inside and outside
interfaces?