Topology
Addressing Table
|
Device
|
Interface
|
IP Address
|
Subnet Mask
|
Default Gateway
|
|
Gateway
|
G0/1
|
192.168.1.1
|
255.255.255.0
|
N/A
|
|
|
S0/0/1
|
209.165.200.225
|
255.255.255.252
|
N/A
|
|
ISP
|
S0/0/0 (DCE)
|
209.165.200.226
|
255.255.255.252
|
N/A
|
|
|
Lo0
|
198.133.219.1
|
255.255.255.255
|
N/A
|
|
PC-A
|
NIC
|
192.168.1.3
|
255.255.255.0
|
192.168.1.1
|
|
PC-B
|
NIC
|
192.168.1.4
|
255.255.255.0
|
192.168.1.1
|
Objectives
Part 1: Build the Network and
Configure Basic Device Settings
Part 2: Troubleshoot Static NAT
Part 3: Troubleshoot Dynamic NAT
Background / Scenario
In this lab, the Gateway router was
configured by an inexperienced network administrator at your company. Several errors
in the configuration have resulted in NAT issues. Your boss has asked you to
troubleshoot and correct the NAT errors and document your work. Ensure that the
network supports the following:
·
PC-A acts as a web server with
a static NAT and will be reachable from the outside using the 209.165.200.254
address.
·
PC-B acts as a host computer
and dynamically receives an IP address from the created pool of addresses
called NAT_POOL, which uses the 209.165.200.240/29 range.
Note: The routers used with CCNA hands-on labs
are Cisco 1941 Integrated Services Routers (ISRs) with Cisco IOS Release 15.2(4)M3
(universalk9 image). The switches used are Cisco Catalyst 2960s with Cisco IOS Release
15.0(2) (lanbasek9 image). Other routers, switches and Cisco IOS versions can
be used. Depending on the model and Cisco IOS version, the commands available
and output produced might vary from what is shown in the labs. Refer to the
Router Interface Summary Table at the end of this lab for the correct interface
identifiers.
Note: Make sure that the routers and switch have been erased and have no
startup configurations. If you are unsure, contact your instructor.
Required Resources
·
2 Routers (Cisco 1941 with
Cisco IOS Release 15.2(4)M3 universal image or comparable)
·
1 Switch (Cisco 2960 with Cisco
IOS Release 15.0(2) lanbasek9 image or comparable)
·
2 PCs (Windows 7, Vista, or XP
with terminal emulation program, such as Tera Term)
·
Console cables to configure the
Cisco IOS devices via the console ports
·
Ethernet and serial cables as
shown in the topology
Part 1:
Build the Network and Configure
Basic Device Settings
In Part 1, you will set up the network
topology and configure the routers with basic settings. Additional NAT-related
configurations are provided. The NAT configurations for the Gateway router
contains errors that you will identify and correct as you proceed through the
lab.
Step 1:
Cable the network as shown in
the topology.
Step 2:
Configure PC hosts.
Step 3:
Initialize and reload the switch
and routers.
Step 4:
Configure basic settings for
each router.
a.
Disable DNS lookup.
b.
Configure device name as shown
in the topology.
c.
Configure IP addresses as listed
in the Address Table.
d.
Set the clock rate to 128000 for DCE serial interfaces.
e.
Assign cisco as the console and vty password.
f.
Assign class as the encrypted privileged EXEC mode password.
g.
Configure logging synchronous to prevent console messages from interrupting the
command entry.
Step 5:
Configure static routing.
a.
Create a static route from the
ISP router to the Gateway router-assigned public network address range 209.165.200.224/27.
ISP(config)# ip
route 209.165.200.224 255.255.255.224 s0/0/0
b.
Create a default route from the
Gateway router to the ISP router.
Gateway(config)# ip route 0.0.0.0 0.0.0.0 s0/0/1
Step 6:
Load router configurations.
The configurations for the routers are
provided for you. There are errors with the configuration for the Gateway
router. Identify and correct the configurations errors.
Gateway Router Configuration
interface
g0/1
ip nat outside
no shutdown
interface
s0/0/0
ip nat outside
interface s0/0/1
no
shutdown
ip nat inside source static 192.168.2.3
209.165.200.254
ip
nat pool NAT_POOL 209.165.200.241 209.165.200.246 netmask 255.255.255.248
ip
nat inside source list NAT_ACL pool NATPOOL
ip
access-list standard NAT_ACL
permit 192.168.10.0 0.0.0.255
banner
motd $AUTHORIZED ACCESS ONLY$
end
Step 7: Save the running configuration to
the startup configuration.
Part 2:
Troubleshoot Static NAT
In Part 2, you will examine the static
NAT for PC-A to determine if it is configured correctly. You will troubleshoot
the scenario until the correct static NAT is verified.
a.
To troubleshoot issues with
NAT, use the debug ip nat command.
Turn on NAT debugging to see translations in real-time across the Gateway router.
Gateway# debug
ip nat
b.
From PC-A, ping Lo0 on the ISP router.
Do any NAT debug translations appear on the Gateway router?
____________________________________________________________________________________
c.
On the Gateway router, enter
the command that allows you to see all current NAT translations on the Gateway router.
Write the command in the space below.
____________________________________________________________________________________
Why are you seeing a NAT translation in
the table, but none occurred when PC-A pinged the ISP loopback interface? What
is needed to correct the issue?
____________________________________________________________________________________
d.
Record any commands that are
necessary to correct the static NAT configuration error.
____________________________________________________________________________________
____________________________________________________________________________________
e.
From PC-A, ping Lo0 on the ISP router.
Do any NAT debug translations appear on the Gateway router?
____________________________________________________________________________________
f.
On the Gateway router, enter
the command that allows you to observe the total number of current NATs. Write
the command in the space below.
____________________________________________________________________________________
Is the static NAT occurring successfully?
Why?
____________________________________________________________________________________
g.
On the Gateway router, enter
the command that allows you to view the current configuration of the router. Write
the command in the space below.
____________________________________________________________________________________
h.
Are there any problems with the
current configuration that prevent the static NAT from occurring?
____________________________________________________________________________________
i.
Record any commands that are
necessary to correct the static NAT configuration errors.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
j.
From PC-A, ping Lo0 on the ISP router.
Do any NAT debug translations appear on the Gateway router?
____________________________________________________________________________________
k.
Use the show ip nat translations verbose command to verify static NAT
functionality.
Note: The timeout value for ICMP is very short. If you do not see all
the translations in the output, redo the ping.
Is the static NAT translation occurring
successfully? ____________________
If static NAT is not occurring, repeat
the steps above to troubleshoot the configuration.
Part 3:
Troubleshoot Dynamic NAT
a.
From PC-B, ping Lo0 on
the ISP router. Do any NAT debug translations appear on the Gateway router?
________________
b.
On the Gateway router, enter
the command that allows you to view the current configuration of the router.
Are there any problems with the current configuration that prevent dynamic NAT
from occurring?
____________________________________________________________________________________
c.
Record any commands that are
necessary to correct the dynamic NAT configuration errors.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
d.
From PC-B, ping Lo0 on the ISP router.
Do any NAT debug translations appear on the Gateway router?
____________________________________________________________________________________
e.
Use the show ip nat statistics to view NAT usage.
Is the NAT occurring successfully?
_______________
What percentage of dynamic addresses has
been allocated? __________
f.
Turn off all debugging using
the undebug all command.
Reflection
1.
What is the benefit of a static
NAT?
_______________________________________________________________________________________
_______________________________________________________________________________________
2.
What issues would arise if 10
host computers in this network were attempting simultaneous Internet
communication?
_______________________________________________________________________________________
_______________________________________________________________________________________
Router Interface Summary Table
|
Router Interface Summary
|
||||
|
Router Model
|
Ethernet Interface #1
|
Ethernet Interface #2
|
Serial Interface #1
|
Serial Interface #2
|
|
1800
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
|
1900
|
Gigabit Ethernet 0/0 (G0/0)
|
Gigabit Ethernet 0/1 (G0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
|
2801
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/1/0 (S0/1/0)
|
Serial 0/1/1 (S0/1/1)
|
|
2811
|
Fast Ethernet 0/0 (F0/0)
|
Fast Ethernet 0/1 (F0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
|
2900
|
Gigabit Ethernet 0/0 (G0/0)
|
Gigabit Ethernet 0/1 (G0/1)
|
Serial 0/0/0 (S0/0/0)
|
Serial 0/0/1 (S0/0/1)
|
|
Note: To find out how the router is configured, look at the interfaces
to identify the type of router and how many interfaces the router has. There
is no way to effectively list all the combinations of configurations for each
router class. This table includes identifiers for the possible combinations
of Ethernet and Serial interfaces in the device. The table does not include
any other type of interface, even though a specific router may contain one.
An example of this might be an ISDN BRI interface. The string in parenthesis
is the legal abbreviation that can be used in Cisco IOS commands to represent
the interface.
|
||||
