Implementation of network address translation in cisco packet tracer
NAT stands for "Network Address
Translation." NAT translates the IP addresses of computers in a local
network to a single IP address. This address is often used by the router that connects the computers to the Internet. Address translation
reduces the need for IPv4 public addresses and hides private network address
ranges.
The Purpose of NAT
NAT serves three main purposes:
·
Enables
a company to use more internal IP addresses. Since they're used internally
only, there's no possibility of conflict with IP addresses used by other
companies and organizations.
·
Allows
a company to combine multiple ISDN connections into a single Internet
connection.
NAT conserves the number of globally
valid IP addresses a company needs, and in combination with Classless
Inter-Domain Routing (CIDR) has done a lot to extend the useful life of IPv4 as a
result.
The NAT mechanism
("natting") is a router feature,
and is often part of a corporate firewall. NAT
gateways can map IP addresses in several ways:
·
From a local IP address to one global IP address statically;
·
From a local IP address to any of a rotating pool of global
IP addresses a company may have;
·
From a local IP address plus a particular TCP port to a
global IP address or one in a pool of ports;
·
From a global IP address to any of a pool of local IP
addresses on a round-robin basis.
Types
of NAT:
Static
NAT:
Static NAT (Network Address
Translation):
Static
NAT (Network Address Translation) is one-to-one mapping of a private IP address to a public IP address. Static
NAT (Network Address Translation) is useful when a network device inside a
private network needs to be accessible from internet.
Dynamic NAT
(Network Address Translation):
Dynamic NAT can be defined as mapping of
a private IP address to a public IP address from a
group of public IP addresses called as NAT pool. Dynamic NAT establishes a
one-to-one mapping between a private IP address to a public IP address. Here
the public IP address is taken from the pool of IP addresses configured on the
end NAT router. The public to private mapping may vary based on the available
public IP address in NAT pool.
·
NAT
conserves legally registered IP addresses .
·
It
provides privacy as the device IP address, sending and receiving the traffic,
will be hidden.
·
Eliminates
address renumbering when a network evolves.
CONFIGURATION:
Topology:
Create
a n/w topology as shown in Figure 7.1. I have taken 2 PCs with IP address as 10.0.0.10, 10.0.0.20. These PCs are
connected to a switch which is connected to a router Router1 with gig 0/1.
The interface IP address of gig 0/1
is 10.0.0.1. The Router1 is connected to Router2 via a serial ports se 0/1/0 in both the routers.
The
interface IP address for Router1 at se 0/1/0 is 100.0.0.1. The interface IP address for Router2 at se 0/1/0 is 100.0.0.2. Router2 is connected to a
server whose IP address is 192.168.1.10 via
gig 0/0 port whose interface IP
address is 192.168.1.1.
Now run the following commands as
below to setup static NAT.
ON ROUTER 1:
Router>en
Router#config t
Enter configuration commands, one per
line. End with CNTL/Z.
Router(config)#int gig 0/1
Router(config-if)#ip address 10.0.0.1
255.0.0.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface
GigabitEthernet0/1, changed state to up
Router(config-if)#int se 0/1/0
Router(config-if)#ip address 100.0.0.1
255.0.0.0
Router(config-if)#no shut
%LINK-5-CHANGED: Interface
Serial0/1/0, changed state to down
Router(config-if)#
Router(config-if)#
%LINK-5-CHANGED: Interface
Serial0/1/0, changed state to up
Router(config-if)#exit
Router(config)#ip nat inside source
static 10.0.0.10 50.0.0.10
Router(config)#int gig 0/1
Router(config-if)#ip nat inside
Router(config-if)#exit
Router(config)#int se 0/1/0
Router(config-if)#ip nat outside
Router(config-if)#exit
Router(config)#ip nat inside source
static 10.0.0.20 50.0.0.20
Router(config)#ip nat inside source
static 10.0.0.30 50.0.0.30
Router(config)#exit
Router(config)#ip route 200.0.0.0
255.255.255.0 100.0.0.2
Router(config)#exit
ON ROUTER 2:
Router>en
Router#config t
Enter configuration commands, one per
line. End with CNTL/Z.
Router(config)#int gig 0/0
Router(config-if)#ip address
192.168.1.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface
GigabitEthernet0/0, changed state to up
Router(config-if)#int se 0/1/0
Router(config-if)#ip address 100.0.0.2
255.0.0.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface
Serial0/1/0, changed state to up
Router(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on
Interface Serial0/1/0, changed state to up
Router(config-if)#ip nat inside source
static 192.168.1.10 200.0.0.10
Router(config)#int gig 0/0
Router(config-if)#ip nat inside
Router(config-if)#exit
Router(config)#int se 0/1/0
Router(config-if)#ip nat outside
Router(config-if)#exit
Router(config)#ip route 50.0.0.0
255.0.0.0 100.0.0.1
Router(config)#exit
Ping snapshot of NAT:
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