ZyXEL Communications ZyWall USG 50-H Series, User Manual

Page: 270 / 704

Chapter 15 HTTP Redirect
ZyWALL USG 50-H User’s Guide
270
15.1.2 What You Need to Know About HTTP Redirect
Web Proxy Server
A proxy server helps client devices make indirect requests to access the Internet or outside
network resources/services. A proxy server can act as a firewall or an ALG (application layer
gateway) between the private network and the Internet or other networks. It also keeps hackers
from knowing internal IP addresses.
A client connects to a web proxy server each time he/she wants to access the Internet. The web
proxy provides caching service to allow quick access and reduce network usage. The proxy
checks its local cache for the requested web resource first. If it is not found, the proxy gets it
from the specified server and forwards the response to the client.
HTTP Redirect, Firewall and Policy Route
With HTTP redirect, the relevant packet flow for HTTP traffic is:
1
Firewall
2 Application Patrol
3
HTTP Redirect
4 Policy Route
Even if you set a policy route to the same incoming interface and service as a HTTP redirect
rule, the ZyWALL checks the HTTP redirect rules first and forwards HTTP traffic to a proxy
server if matched. You need to make sure there is no firewall rule(s) blocking the HTTP
requests from the client to the proxy server.
You also need to manually configure a policy route to forward the HTTP traffic from the
proxy server to the Internet. To make the example in
Figure 207 on page 269 work, make sure
you have the following settings.
For HTTP traffic between lan1 and dmz :
• a from LAN1 to WAN firewall rule (default) to allow HTTP requests from lan1 to dmz .
Responses to this request are allowed automatically.
• an application patrol rule to allow HTTP traffic between lan1 and dmz .
• a HTTP redirect rule to forward HTTP traffic from lan1 to proxy server A .
For HTTP traffic between dmz and wan1 :
• a from DMZ to WAN firewall rule (default) to allow HTTP request from dmz to wan1 .
Responses to this request are allowed automatically.
• a application patrol rule to allow HTTP traffic between dmz and wan1 .
• a policy route to forward HTTP traffic from proxy server A to the Internet.
Finding Out More
See Section 5.4.15 on page 88 for related information on these screens.
15.2 The HTTP Redirect Screen
To configure redirection of a HTTP request to a proxy server, click Network > HTTP
Redirect . This screen displays the summary of the HTTP redirect rules.