Network Address Translation

Network Address Translation is used translate the private IP into Public IP. It is do mapping.

Types of NAT:

1. Static NAT
2. Dynamic NAT
3. Overloading

1. Static Network Address Translation

It translate the one private IP into one Public IP, it also called 1-1 mapping

i.e. 192.168.10.1— 200.100.100.1

For Example:

LAN IP scheme is 192.168.10.0, and want to do nat for only one Private IP (192.168.10.1) to the one public IP 200.100.100.1

Public IP is 200.100.100.1

So Static NAT will be as

• Router# conf terminal
• Router(config)# int e0
• Router(config_if)# ip add 192.168.10.10 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# exit
• Router(config)# int s0
• Router(config_if)# ip add 1.1.1.1 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# clock rate 6400
• Router(config_if)# router rip

If we want to configure on RIP v2 so do as

• Router(config_router)# version v2
• Router(config_router)# network 192.168.10.10
• Router(config_router)# network 1.0.0.0
• Router(config_router)# exit
• Router(config)# ip nat inside source static 192.168.10.1 200.100.100.1
• Router(config)# int e0
• Router(config_if)# ip nat inside
• Router(config_if)# exit
• Router(config_if)# int s0
• Router(config_if)# ip nat outside
• Router(config_if)# exit
• Router(config)# exit
• Router#

2. Dynamic Network Address Translation:

Dynamic NAT is used to translate the number of Private IP into the number of Public ip (ip pool)

For Example:

LAN IP scheme is: 192.168.10.0

Public Ip pool is: 200.100.100.1 200.100.100.10

Serial 0 ip is: 1.1.1.1

So the configuration will be as:

• Router# conf terminal
• Router(config)# int e0
• Router(config_if)# ip add 192.168.10.10 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# exit
• Router(config)# int s0
• Router(config_if)# ip add 1.1.1.1 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# clock rate 6400
• Router(config_if)# router rip

If we want to configure on RIP v2 so do as

• Router(config_router)# version v2
• Router(config_router)# network 192.168.10.10
• Router(config_router)# network 1.0.0.0
• Router(config_router)# exit
• Router(config)# ip nat pool mypool 1.1.10 1.1.1.20 netmask 255.0.0.0
• Router(config)# ip nat inside source list 100 pool mypool
• Router(config)# access-list 100 permit IP 192.168.10.0 0.0.0.255 any
• Router(config)# int e0
• Router(config_if)# ip nat inside
• Router(config_if)# exit
• Router(config)# int s0
• Router(config)# ip nat outside
• Router(config)#exit

3. Overload or Port Address Translation:

PAT or Overload NAT is used to do mapping to only one public IP for all the LAN IP.

For Example:

LAN IP scheme is: 192.168.10.0

Pubic IP is: 1.1.1.1 which is our S0

• Router# conf terminal
• Router(config)# int e0
• Router(config_if)# ip add 192.168.10.10 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# exit
• Router(config)# int s0
• Router(config_if)# ip add 1.1.1.1 255.255.255.0
• Router(config_if)# no shut
• Router(config_if)# clock rate 6400
• Router(config_if)# router rip

             If we want to configure on RIP v2 so do as

• Router(config_router)# version v2
• Router(config_router)# network 192.168.10.10
• Router(config_router)# network 1.0.0.0
• Router(config_router)# exit
• Router(config)# ip nat inside source list 100 int so overload
• Router(config)# access-list 100 permit ip 192.168.10.0 0.0.0.255 any
• Router(config)# int e0
• Router(config_if)# ip nat inside
• Router(config_if)# exit
• Router(config)# int s0
• Router(config)# ip nat outside
• Router(config)#exit

We can do overload in dynamic method as:

• Router(config)# router rip
• Router(config_router)# version v2
• Router(config_router)# network 192.168.10.10
• Router(config_router)# network 1.0.0.0
• Router(config_router)# exit
• Router(config)# ip nat pool mypool 1.1.1.1 1.1.1.1 netmask 255.0.0.0
• Router(config)# ip nat inside source list 100 pool mypool overload
• Router(config)# access-list 100 permit ip 192.168.10.0 0.0.0.255 any
• Router(config)# int e0
• Router(config_if)# ip nat inside
• Router(config_if)# exit
• Router(config)# int s0
• Router(config)# ip nat outside
• Router(config)#exit

 IOS (internetwork Operating System) Loading (Recovery and Backup) of Router:

Requirements:

1. TFTP server (solar-wind TFTP server)
2. A system connected with LAN for the purpose of TFTP software installation as

TFTP— Open it—File Configure

Select the 3^rd option i.e. (Terminal and Replace…). It will make in a directory with name C:TFTP root in C: drive in that LAN system. Copy the IOS image file and paste in C:TFTP server directory. Now go to router and do the following configuration

• Router# copy tftp flash
• Router# ……… []? 10.0.0.10 (the TFTP server ip address)
• Router#…………. []? Mc381-ismg.1207f (file name of IOS in backup)
• Router#…………. []? Press Y. (confirmation message)
• Router# reload

To take Backup of IOS to a system:

• Router# copy flash tftp
• Router# ……… []? 10.0.0.10 (the TFTP server ip address)
• Router#…………. []? Mc381-ismg.1207f (file name of IOS in backup)
• Router#…………. []? Press Y. (confirmation message)
• Router#