Proxy server routing analysis

For small user groups or home users to access the Internet, dial-up Internet access is a cheap and practical way. The problem of multi-user shared access to the Internet can be solved by the proxy server software on the local area network. The proxy server is essentially a bridge between the user group and the Internet to realize the access of the network users to the Internet.

Using LAN

At present, there are many networking products in the LAN, and the Ethernet switch or hub (HUB) is inexpensive, which is very easy to realize the interconnection of LAN customers. This article takes the existing campus network as an example to illustrate how to use the PROXY proxy server to implement Internet connection and perform internal route analysis of the proxy server. The topology of the local area network is shown in Figure 1. The local area network consists of several clients, one server, one dial-up network server, and one modem connected to the Internet.

The specific configuration is as follows:

1. Client: Install WINDOWS 95/98, IE browser (Internet Explorer 4.0 or 5.0). In the Internet Explorer option, select the proxy server to access the Internet, and fill in the IP address and port number (80) of the proxy server with the address and port entries. This completes the simple configuration of the client.

2. Server: Install WINDOWS NT and PROXY software. Configure the server's RAS, dial-up network, TCP/IP, etc., establish a WINDOWS user account, start the PROXY software, start the WEB, FTP and other proxy tasks and set the permissions, and give the client access to the Internet.

3. Modem: Configure a modem (MODEM) on the server side, a telephone line. Dial local Internet calls, such as 169, 163, etc.

4. Dial-up network server: Provides services for remote users in the LAN, enabling remote users to connect to the LAN through dedicated communication lines.

Routing Problem with Proxy Server

After configuring the RAS service and dial-up network of the server, dial-up connection. In this case, there are two interface cards in the proxy server, namely a network card and a modem. It can be regarded as a router to provide routing and forwarding functions for customers and the outside world. Therefore, it is necessary to view and adjust the routing settings of the server. Ensure normal communication between the server and the customer.

Dial the server and view the routing table of the server through the ROUTE command in DOS mode. The following uses the default route as an example to simply analyze the routing table of the NT server in the dialing process, assuming that 10.119.40.254 is the gateway of the network segment where the server is located, and 10.119.40.49 is the IP address of the NT server NIC.

Pre-Dial Server Routing Table (Table 1):

NETWORK ADDRESS NETMASK GATEWAY ADDRESS INTERFACE METRIC

0.0.0.0 0.0.0.0 10.119.40.254 10.119.40.49 1

Server Routing Table after Dialing (Table 2):

NETWORK ADDRESS NETMASK GATEWAY ADDRESS INTERFACE METRIC

0.0.0.0 0.0.0.0 10.119.40.254 10.119.40.49 2

0.0.0.0 0.0.0.0 10.18.168.168 10.18.168.168 1

where 10.18.168.168 is the IP address assigned to the dial-up network (modem) by the INTERNET server. By comparing Tables 1 and 2, the default route before and after dialing has changed. This phenomenon is mainly analyzed because the dial-up network in the server and the TCP/IP setting option have chosen to use the default gateway of the dial-up network, so that the server first sends information to the customers on the 10.119.40.0 network segment. 10.18.168.168 address. When customers on the network request access to the INTERNET site, they must go through the LAN to the NT server and then to the MODEM. Therefore, the normal connection between the client and the server must be ensured, so that the routing process is performed through the 10.119.40.49 LAN card. When the PING command is used for detection, the server can ping the client, and the client PING server has a timeout (TIME OUT). This phenomenon indicates that the default route of the proxy server has changed, so that the connection between the client and the server is first forwarded through 10.18.168.168. To solve this problem, you need to make the following settings. Assume that a customer's network segment is 122.103.1.0, SUBMASK: 255.255.255.0, and you need to add the specified item to the routing table, that is, execute the command ROUTE ADD 122.103.1.0 255.255.255.0 10.119.40.49 . 10.119.40.49 is the IP address of the NT server's network card. Then check the server routing table as follows:

NETWORK ADDRESS NETMASK GATEWAY ADDRESS INTERFACE METRIC

0.0.0.0 0.0.0.0 10.119.40.254 10.119.40.49 2

0.0.0.0 0.0.0.0 10.18.168.168 10.18.168.168 1

122.103.1.0 255.255.255.0 10.199.40.254 10.119.40.49 1

Further analysis, we also You can achieve this by modifying the default route by using ROUTE ADD 0.0.0.0 0.0.0.0 10.119.40.49 1 IF METRIC=2

Set the routing table to:

NETWORK ADDRESS NETMASK GATEWAY ADDRESS INTERFACE METRIC

0.0.0.0 0.0.0.0 10.119.40.254 10.119.40.49 1

As a special case, we analyze the routing problem of remote users on the LAN. There are remote users on the LAN, they are usually connected to the LAN via a dedicated communication line. If they try to access the Internet through a proxy server, the routing table must be configured on the NT server. Since such remote users need to go through two dial-up services to access the Internet, direct routing settings on the PROXY proxy server are especially necessary. As mentioned above, customers on the LAN can also connect the server to the client by modifying the default route. For remote clients, it is not necessary to set the proxy server's route directly. Assume that the remote user (Dial-up Network Server) is on the network segment 122.100.1.0, SUBMASK: 255.255.255.0, and must be added to the route: ROUTE ADD 122.100.1.0 255.255.255.0 10.119.40.49 to ensure the remote user's pass-through. Otherwise, when the customer dials the LAN, the remote client can PING all other devices on the network, but the PING NT server has a timeout error. This means that the proxy server's default route does not work at this time.

User Management

Each agent user can be managed by WINDOWS NT. When the client accesses the INTERNET, the user authentication is first performed on the proxy server. When the user inputs the normal username and password, the INTERNET service can be provided for the user, and then the INTERNET is accessed through the proxy server. Proxy server software can use MS PROXY 2.0, which provides a large number of proxy permissions, which can be used to easily manage, monitor, record, etc. authorized users, access sites, and more.