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Lesson 8Determining Proxy Server Client Requirements
ObjectiveIdentify the Proxy Server Client Requirements to be included in the Proxy Server Design

Determining Proxy Server Client Requirements

You must determine the Proxy Server client requirements so that you can specify the private network address ranges and select the appropriate software for connecting to Proxy Server.

Specifying private network IP address ranges

You must identify the IP address ranges within the private network so that you can specify these address ranges in the Proxy Server design. Proxy Server clients can then determine if the destination IP address in an IP packet must be sent directly to the private network destination or forwarded to the proxy server.
The IP address ranges that you specify are stored in the local address table (LAT) file on the proxy server. When requests are sent to the proxy server, the proxy server uses the LAT to determine if the request is within the private network or on the Internet.
The following Slide Show describes:

  1. Computers on the private network may or may not use Proxy Server client software.
  2. For computers on the private network that do not have the Proxy Server Client software, you must specify the IP address of the proxy server's private network interface as the default gateway.
  3. Because the proxy server is the default gateway for the computer, all requests that are not on the computer's local subnet are forwarded to the proxy server, which forwards the request to the internet.
  4. When the computers on the private network have Proxy Server client software installed , they have a local copy of the LAT file.
  5. The Proxy Server clients use their local copy of the LAT file to determine if incoming requests have destinations within the private network or on the internet.
  6. Private network requests are sent to the destination within the private network without proxy server intervention, while internet requests are sent to the proxy server.

Computers On PrivateNetwork with Without Proxy Server Client

Selecting software for connection to Proxy Server

You can specify that the private network interface of the proxy server is the default gateway entry for computers on the private network.
If you specify the proxy server as the default gateway, the private network traffic increases because all traffic destined for other subnets in the private network is forwarded first to the proxy server and then on to the final destination. In order to prevent this, specify that the private network computers be configured with software to forward traffic to the proxy server if the final destination is the Internet.
The following table lists the software options for private network computers and the reason to include the options in your design.

Select: If you need to support:
Microsoft® Internet Explorer 10.0 HTTP and FTP traffic only Any operating system that includes Internet Explorer 5.0 Packet filters and domain filters for filtering traffic
Proxy Server client All IP protocol traffic Any operating system that supports the WinSock standard Packet filters and domain filters for filtering traffic IPX/SPX-based private networks
SOCKS All IP protocols supported by the SOCKS applications UNIX, Macintosh, or operating systems that run SOCKS-compatible applications SOCKS rules, protocol rules, and IP-packet filters for filtering traffic
No client software All IP protocols Any operating system with the default gateway configured to send Internet traffic to the proxy server Protocol rules, and IP-packet filters for filtering traffic

Question: When a computer on the private network does not have Proxy Server Client software, what do you need to specify as the default gateway?
Answer: The IP address of the proxy server's private network interface
The next lesson wraps-up this module.