Verifying NAT and PAT Configurations

Last Updated on Wed, 28 Jun 2023 | Portable Command

Router#show ip nat translations	Displays the translation table
Router#show ip nat statistics	Displays NAT statistics
Router#clear ip nat translations inside a.b.c.d outside e.f.g.h	Clears a specific translation from the table before it times out
Router#clear ip nat translations*	Clears the entire translation table before entries time out
Troubleshooting NAT and PAT Configurations
Router#debug ip nat	Displays information about every packet that is translated. Be careful with this command. The router's CPU might not be able to handle this amount of output and might therefore hang the system.
Router#debug ip nat detailed	Displays greater detail about packets being translated.

Figure 23-1 shows the network topology for the PAT configuration that follows using the commands covered in this chapter.

Figure 23-3 Port Address Translation Configuration

ISP Router

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How to configure nating on cisco router?

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Access the router's command-line interface (CLI).

Enter configuration mode by typing the command “enable” and enter the privileged mode password.

Create a static route to the remote network; for example:Router(config)# ip route 10.0.0.0 255.0.0.0 10.0.0.

1 Create an access list to define which traffic can be sent through the static route.Router(config)# access-list 1 permit 10.0.0.0 0.0.0.

255 Enter configuration mode for the interface that will be used to route traffic.Router(config)#interface <interface name>

Configure the interface to use NAT by typing the command “ip nat outside”.

Assign the access list to the interface.Router(config-if)# ip nat outside access-list

1 Exit configuration mode by typing “exit”.

Save the configuration.Router# write memory

router>enable	Moves to privileged mode.
router#configure terminal	Moves to global configuration mode.
router(config)#host ISP	Sets the host name.
ISP(config)#no ip domain-lookup	Turns off Domain Name System (DNS) resolution to avoid wait time due to DNS lookup of spelling errors.
ISP(config)#enable secret cisco	Sets the encrypted password to cisco.
ISP(config)#line console 0	Moves to line console mode.
ISP(config-line)#login	User must log in to be able to access the console port.
ISP(config-line)#password class	Sets the console line password to class.
ISP(config-line)#logging synchronous	Commands will be appended to a new line.
ISP(config-line)#exit	Returns to global configuration mode.

Figure 23-3 Port Address Translation Configuration

Network 172.16.10.0/24 Network 198.133.219.0/30

IP NAT IP NAT Inside Outside

ISP(config)#interface serial 0/0/1	Moves to interface configuration mode.
ISP(config-if)#ip address 198.133.219.2 255.255.255.252	Assigns an IP address and netmask.
ISP(config-if)#clock rate 56000	Assigns the clock rate to the DCE cable on this side of the link.
ISP(config-if)#no shutdown	Enables the interface.
ISP(config-if)#interface loopback 0	Creates loopback interface 0 and moves to interface configuration mode.
ISP(config-if)#ip address 192.31.7.1255.255.255.255	Assigns an IP address and netmask.
ISP(config-if)#exit	Returns to global configuration mode.
ISP(config)#exit	Returns to privileged mode.
ISP#copy running-config startup-config	Saves the configuration to NVRAM.
Company Router
nouten>enable	Moves to privileged mode.
router#configure terminal	Moves to global configuration mode.
router(config)#host Company	Sets the host name.
Company(config)#no ip domain-lookup	Turns off DNS resolution to avoid wait time due to DNS lookup of spelling errors.
Company(config)#enable secret cisco	Sets the secret password to cisco.
Company(config)#line console 0	Moves to line console mode.
Company(config-line)#login	User must log in to be able to access the console port.
Company(config-line)#password class	Sets the console line password to class.
Company(config-line)#logging synchronous	Commands will be appended to a new line.

Company(config-line)#exit	Returns to global configuration mode.
Company(config)#interface fastethernet 0/0	Moves to interface configuration mode.
Company(config-if)#ip address 172.16.10.1 255.255.255.0	Assigns an IP address and netmask.
Company(config-if)#no shutdown	Enables the interface.
Company(config-if)#interface serial 0/0/0	Moves to interface configuration mode.
Company(config-if)#ip address 198.133.219.1 255.255.255.252	Assigns an IP address and netmask.
Company(config-if)#no shutdown	Enables the interface.
Company(config-if)#exit	Returns to global configuration mode.
Company(config)#ip route 0.0.0.0 0.0.0.0 198.133.219.2	Sends all packets not defined in the routing table to the ISP router.
Company(config)#access-list 1 permit 172.16.10.0 0.0.0.255	Defines which addresses are permitted through; these addresses are those that will be allowed to be translated with NAT.
Company(config)#ip nat inside source list 1 interface serial 0/0/0 overload	Creates NAT by combining list 1 with the interface serial 0/0/0. Overloading will take place.
Company(config)#interface fastethernet 0/0	Moves to interface configuration mode.
Company(config-if)#ip nat inside	Location of private inside addresses.
Company(config-if)#interface serial 0/0/0	Moves to interface configuration mode.
Company(config-if)#ip nat outside	Location of public outside addresses.
Company(config-if)#@-@	Returns to privileged mode.
Company#copy running-config startup-config	Saves the configuration to NVRAM.

This chapter provides information and commands concerning the following topics:

• Configuring DHCP

• Verifying and troubleshooting DHCP configuration

• Configuring a DHCP helper address

• DHCP client on a Cisco IOS Software Ethernet interface

• Configuration example: DHCP

Continue reading here: Configuration Example DHCP

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Verifying NAT and PAT Configurations

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