The HTTP Host header contains the domain name and port. You might want to create a rule to rewrite the port so you can harmonize port numbers that are correlated with your application service. For example, suppose you want to avoid parsing reports on your backend servers that show requests to many HTTP service ports. When you review your aggregated reports, you have records for port 80, port 8080, and so on. You would rather have all HTTP requests served on port 80 and accounted for on port 80. To support this plan, you can rewrite the HTTP request headers so that all the Host header in all HTTP requests shows port 80.

Figure 32 shows an HTTP request rule that uses a regular expression to match HTTP Host headers for www.example.com with any port number and change it to port 80.