Displaying or Blocking a Private IP Address
This section outlines the strategy that the application follows to display or block a private IP address in a corresponding sub-net.
- Private IP address – A private IP address is a non-Internet facing IP address on an internal network.
Private IP addresses are provided by network devices, such as routers, using network address translation (NAT).
- Virtual IP address – A virtual IP address (VIPA) is an IP address that is assigned to multiple domain names or servers that share an IP address based on a single network interface card (NIC).
VIPAs are allocated to virtual private servers, websites, or any other application that resides on a single server. The host server for these applications has a network IP address that is assigned by a network administrator, whereas the different server applications have VIPAs. VIPAs enhance network load balancing and redundancy.
- Automatic Private IP Addressing – Automatic Private IP Addressing (APIPA) is a feature of Windows-based operating systems that enable a computer to automatically assign itself an IP address when no Dynamic Host Configuration Protocol (DHCP) server is available to perform that function.
APIPA serves as a DHCP server failover mechanism and makes it easier to configure and support small local area networks.
- Private IP Address Range – The following is the IP address range which falls under either the private, (or) Virtual, (or) APIPA category:
-
NAT –
10.0.0.0 - 10.255.255.255
- Private (or) Virtual –
172.16.0.0 - 172.31.255.255
or192.168.0.0 - 192.168.255.255
-
APIPA –
169.254.0.0
to169.254.255.255
-
Use Case | Standalone / Client | Remarks |
---|---|---|
No NIC CARD (Windows) | Loopback (or) 127.0.0.1 | As the server is not in network, the gateway cannot access the standalone server. |
No NIC CARD (Linux) | Loopback (or) 127.0.0.1 | Because the server is not in network, the gateway cannot access the standalone server. |
Static IP | Using Static IP | — |
DHCP IP | Using the DHCP IP | — |
Private IP | Using the Private IP | In a more secured environment, private IP address cannot be accessed outside the server. |
Use Case | Standalone / Client | Remarks |
---|---|---|
No NIC CARD (Windows) | Loopback (or) 127.0.0.1 | As the server is not in network, the gateway cannot access the standalone server. |
No NIC CARD (Linux) | Loopback (or) 127.0.0.1 | Because the server is not in network, the gateway cannot access the standalone server. |
Static IP | Using Static IP | — |
DHCP IP | Using the DHCP IP | — |
Private IP | If a valid IP exists, it is displayed. If no valid IP exists, Loopback (or) 127.0.0.1 is displayed. | In a more secured environment, because a private IP address cannot be accessed outside the server, the application does not populate a private IP address. |
Why does the application blocks certain IP addresses: In an enterprise world, when a computer is assigned a private IP address, the local devices see this computer through its private IP address. However, devices residing outside of your local network cannot directly communicate through the private IP address, but uses your router's public IP address to communicate. You must use a NAT router to directly access a local device assigned a private IP address.
In a more secure environment, although the application is able to discover and display the private IP address through the gateway server, when a request is made through the gateway server, the private IP is not accessible. Because the application cannot access the private IP, the application is unable to service the requests which are meant for the private IP.
Because of the previously mentioned reason, when the installation is a gateway, the corresponding gateway server is not able to communicate with the private IP address which in turn becomes an issue. The application works if the private IP addresses are behind the NAT router, which is the most preferable option in an enterprise world.
The diagram that follows shows how a private IP address should be accessed in enterprise networks and the problems with the private IP address:
