Advanced Forwarding

Forwarding rule

There are six types of forwarding rules: domain name, URL, HTTP request method, HTTP header, query string, and CIDR block

For details, see Forwarding Rule.

Action

The following actions are supported: forward to a backend server group, redirect to another listener, redirect to another URL, and return a specific response body.

For details, see Action Types.

Domain name

• Description

  Route requests based on the domain name.

  • You can configure multiple domain names in a forwarding policy. Each domain name contains at least two labels separated by periods (.). Max total: 100 characters. Max label: 63 characters.
  • Each label can contain letters, digits, hyphens (-), periods (.), and asterisks (*). A label must start with a letter, digit, or asterisk (*) and cannot end with a hyphen (-). An asterisk (*) must be used as the leftmost label if you want to configure a wildcard domain name.
• Matching rules

  Exact match domains and wildcard domains are supported.

Example
Request URL: https://www.example.com/login.php?locale=en-us=#videos
Domain name in the forwarding rule: www.example.com

URL

• Description

  Route requests based on URLs. You can configure multiple URLs in a forwarding policy. A URL can contain letters, digits, and special characters _~';@^-%#$.*+?,=!:|\/()[]{}.

  If the URL contains special characters such as question marks (?) or pound keys (#), escape the special characters before configuring the forwarding rule.

• Matching rules
  • Exact match: The request URL must exactly match that specified in the forwarding policy. The URL must start with a slash (/) and can use asterisks (*) and question marks (?) as wildcards.
  • Prefix match: The requested URL starts with the specified URL string. The URL must start with a slash (/) and can use asterisks (*) and question marks (?) as wildcard characters.
  • Regular expression match: The URLs are matched using a regular expression.

For more information about URL matching rules, see URL Matching.

Example
Request URL: https://www.example.com/login.php?locale=en-us#videos
URL in the forwarding rule: /login.php

Query string

Route requests based on the query string.

Example
Request URL: https://www.example.com/login.php?locale=en-us#videos
A query string needs to be configured for the forwarding rule:
Key: locale
Value: en-us

HTTP request method

Route requests based on the HTTP method.

• You can configure multiple request methods in a forwarding policy.
• The following methods are available: GET, POST, PUT, DELETE, PATCH, HEAD, and OPTIONS.

Example
GET

HTTP header

Route requests based on the HTTP header.

Example
Key: Accept-Language
Value: en-us

CIDR block

Route requests based on the source IP addresses from where requests originate.

Example
192.168.1.0/24 or 2020:50::44/127

Forward to a backend server group

Requests are forwarded to the specified backend server group.

Redirect to another listener

Requests are redirected to another listener, which then routes the requests to its associated backend server group.

NOTE:

If you select Redirect to another listener and create a redirect for the listener, it will redirect the requests to the specified HTTPS listener, but access control configured for the listener will still take effect.

For example, if you configure a redirect for an HTTP listener, HTTP requests to access a web page will be redirected to the HTTPS listener you select and handled by the backend servers associated with the HTTPS listener. As a result, the clients access the web page over HTTPS. The configuration of the HTTP listener will become invalid.

Redirect to another URL

Requests are redirected to the configured URL.

When clients access website A, the load balancer returns 302 or any other 3xx status code and automatically redirects the clients to website B. You can custom the redirection URL that will be returned to the clients.

Example
URL for redirection: http://www.example1.com/index.html?locale=en-us#videos
Protocol: HTTP
Domain name: www.example1.com
Port: 8081
Path: /index.html
Query String: locale=en-us
HTTP Status Code: 301

Return a specific response body

Load balancers return a fixed response to the clients.

You can custom the status code and response body that load balancers directly return to the clients without the need to route the requests to backend servers.

Example

text/plain

Sorry, the language is not supported.

text/css

<head><style type="text/css">div {background-color:red}#div {font-size:15px;color:red}</style></head>

text/html

<form action="/" method="post" enctype="multipart/form-data"><input type="text" name="description" value="some text"><input type="file" name="myFile"><button type="submit">Submit</button></form>

application/javascript

String.prototype.trim = function() {var reExtraSpace = /^\s*(.*?)\s+$/;return this.replace(reExtraSpace, "$1")}

application/json

{ "publicip": { "type": "5_bgp","ip_version": 4},"bandwidth": {"name": "bandwidth123","size": 10,"share_type": "PER"}}

NOTE:

Ensure that the response body does not contain carriage return characters. Otherwise, it cannot be saved.

/elb/abc.html

Forwarding policy 01

/elb/abc.html

Prefix match

1

Backend server group 01

Forwarding policy 02

/elb

Prefix match