To configure an ISDN connection between our Office router and
the ISP's router, and configure dynamic 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 has a large
number of computers it would be too time consuming to enter all of
the static address translations into the router. Our alternative is
dynamic 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 secret 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 dynamic network address
translation is to define a pool of inside global addresses (real
IP addresses) to be allocated as needed. Enter the global
configuration prompt on the Office router and enter the following
commands:
Office(config)#ip nat pool net-10 206.222.222.1 206.222.222.254
netmask
255.255.255.0
Why is it important to include the netmask information?
Now we need to define a standard access list permitting those
addresses that are to be translated from the inside network.
Next we need to enter a command which will dynamically link our
pool of real addresses with our list of inside addresses for
translation.
Office(config)#ip nat inside source list 2 pool net-10
What does "pool net-10" mean in the preceding command?
The final part of the configuration is to tell the router which
interface is the inside interface and which is the outside interface.
The inside interface is the one that connects to our internal network
and the outside interface is the one that typically connects to the
Internet.
Finally it is time to verify that NAT is operating correctly on
our Office router.
Office#show ip nat translations
What information did the router respond with?
Office#show ip nat statistics
What information did the router respond with?
Now for testing NAT. Don't forget to add a static route back to
your global network on the ISP router. From a workstation on the
inside network, ping an address on the outside (workstation on the
network off of the ISP router).
Office#show ip nat translations
What information did the router respond with?
Office#show ip nat translations verbose
What information did the router respond with?
Office#show ip nat statistics
What information did the router respond with?
Now change the IP address on the workstation on network
10.30.30.0 to 10.30.30.30, and reboot the computer. After the computer
reboots ping an address on the outside.
Office#show ip nat translations
What new piece of information did the router respond with?
Could we use static translation and dynamic translation at the same
time on the same router?