Contents of this article
In this article i describe the dynamic network address translation in routers. NAT Network Address Translation defined in router to identify the different devices for different network traffic. NAT Network Address Translation is a method to allow multiple devices to access internet on a single public IP address. To access internet by a device required an unique address known as public IP address.
We know the IP addresses are limited and it is not possible to allot each device a unique IP address. To resolve this problem private IP address used with NAT Network Address Translation. Almost organisations used single Public IP address and allow their multiple users to access internet. This facility provided by NAT Network Address Translation.
The translation of private IP address to a public address done by NAT Network Address Translation. For translation inside local IP address converted to inside Global address . In simple words we can say NAT Network Address Translation allow the local hosts to access internet with single public IP address. Various web services accessible on particular port numbers like FTP on 21. These port numbers of various services helps to access the internet by local hosts. NAT Network Address Translation works on Network layer of OSI or TCP/IP model.
Requirement of NAT Network Address Translation
NAT is mostly used when a LAN required internet access for all devices of LAN. In this case you do not have public IP address for your each device. NAT works fine with single public IP address and provide internet service to all your devices. Another situation is when you want to change your ISP and required to reconfigure your local network. NAT allow to change the ISP without any changing in local network IP address scheme. NAT is also beneficial when two intranet required to merge with duplicate IP addresses.
Dynamic Network Address Translation
The dynamic network address translation is a type of NAT technique used to map the local IP address with Global IP addresses in router. dynamic network address translation allow internet access to computers, servers of a private LAN. We know in a LAN we use private IP addresses which are not rout on internet routers.
Dynamic network address translation mostly used in the networks where a range of public IP address is available. Dynamic NAT used when Local computers required to access a fix range of public IP address to access the internet. Suppose our local network computers need to access multiple public IP addresses dynamically then dynamic NAT required to configure in local router.
Dynamic network address translation provides our local Network IP address to map with multiple public IP addresses. We can say many local IP address map with many public IP address by using the dynamic network address translation.
Dynamic network address translation explained
Dynamic network address translation allow the local network to communicate with the public network by using multiple public addresses. Router understand the incoming traffic from multiple sources. We create a filter on router to allow for particular traffic in the local network. In static NAT configuration we allow only single public IP address to permit in the network.
In Dynamic NAT we allow a range of IP addresses to permit in the network. We create a pool of IP ranges of public IP addresses. Router allow only the IP address which lie in the pool. The pool mapped with local IP address so local computer can access the incoming traffic from a predefined network only. This practice provides an additional layer of security to our local network.
Configuration of static network address translation.
Suppose we have a network as shown in below image. Here the local network hosts assign the IP address of range 192.168.1.0/24 and the gateway is 192.168.1.1 for each device. The public IP address pool required to communicate with our local network is 170.20.24.10 to 170.20.24.200 with netmask of 24.
We know the Dynamic NAT required a pool of public addresses and a network ID of own local IP network. Dynamic Nat is useful when you need to access a particular network not internet. Because internet services have many unknown IP address. So do not assign the dynamic NAT on computers which require to access the internet.
let’s come to the point, we have three PC which have IP range of 192.168.1.1/24 network. The gateway of local network is assigned at the GigabitEthernet0/0 port of Router. A public IP range of 170.20.24.10 to 170.20.24.200 of mask 255.255.255.0 is required to communicate with our local network. The public network is connected with the GigabitEthernet0/1 or router. The IP address or GigabitEthernet0/1 is 170.20.24.10/24.
Firstly configure the router to assign the IP addresses to both interfaces by running the below commands.
Router>en Router#config t Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface gigabitethernet0/0 Router(config-if)#ip address 192.168.1.1 255.255.255.0 Router(config-if)#exit Router(config)#interface gigabitethernet0/1 Router(config-if)#ip address 170.20.24.10 255.255.255.0 Router(config-if)#exit Router(config)#do wr Building configuration... [OK] Router(config)# Router#
After running the above commands assign the IP addresses to the Pcs of local network as shown in above picture. Now the time to configure the dynamic network address translation in router. See the below commands for configuration of dynamic network address translation.
Router>en Router#config t Enter configuration commands, one per line. End with CNTL/Z. Router(config)#ip nat pool dynamicnat 170.20.24.10 170.20.24.200 netmask 255.255.255.0 Router(config)#do wr Building configuration... [OK] Router(config)#
After running above command the dynamic NAT pool created whose name is dynamic nat. Now create an access list to permit the IP address of local pools by running the below command.
Router>en Router#config t Enter configuration commands, one per line. End with CNTL/Z. Router(config)#access-list 10 permit 192.168.1.0 255.255.255.0 Router(config)#do wr Building configuration... [OK] Router(config)#
We have successfully created an access list to permit the network Id 192.168.1.0/24 through the router. Now map the access list with NAT pool. After mapping assign the access list to the interfaces of router by running the below command.
Router>en Router#config t Router(config)#ip nat inside source list 10 pool dynamicnat Router(config)#interface gigabitethernet0/0 Router(config-if)#ip nat inside Router(config-if)#exit Router(config)#interface gigabitethernet0/1 Router(config-if)#ip nat outside Router(config-if)#exit Router(config)#do wr Building configuration... [OK] Router(config)#
I hope you found this article helpful related to Dynamic NAT configuration for CCNA Exam. For any query or suggestions you may Drop a comment below or contact us. Your suggestions are always welcome by us.
