After creating a CLB instance, you need to configure a listener to it. The listener listens to requests on the instance and routes traffic to real servers based on the load balancing policy.
You need to configure the following for a CLB listener:
A CLB listener can listen to layer-4 and layer-7 requests on a CLB instance and route them to real servers for processing. The main difference between layer-4 CLB and layer-7 CLB is whether layer-4 or layer-7 protocol is used to forward traffic for load balancing of user requests.
Tencent Cloud CLB supports request forwarding over the following protocols:
- The TCP SSL listener feature is currently in beta test. To try it out, please submit a ticket for application.
- The TCP SSL listener feature is only available to public network CLB but not private network CLB or classic CLB.
|TCP||Connection-oriented and reliable transport layer protocol
||TCP is suitable for scenarios that have high requirements for reliability and data accuracy but relatively low requirements for transfer speed, such as file transfer, receiving and sending emails, and remote login.
For more information, please see Configuring TCP Listener.
|UDP||Connection-less transport layer
||UDP is suitable for scenarios that have high requirements for transfer speed but relatively low requirements for accuracy, such as instant messaging and online videos.
For more information, please see Configuring UDP Listener.
|TCP SSL||Secure TCP
||TCP SSL is suitable for scenarios that have high requirements for security when TCP protocol is used and supports TCP-based custom protocols.
For more information, please see Configuring TCP SSL Listener.
If you use layer-4 listener (i.e., layer-4 protocol forwarding), CLB instance will establish a TCP connection with the real server on the listener port, and directly forward requests to the real server. This process does not modify any data packets (in passthrough mode) and has high forwarding efficiency.
|HTTP||Application layer protocol
||HTTP is suitable for applications that need to identify request content, such as web applications and app services.
For more information, please see Configuring HTTP Listener.
|HTTPS||Encrypted application layer protocol
||HTTPS is suitable for HTTP applications that need encrypted transmission.
For more information, please see Configuring HTTPS Listener.
|Listening port (frontend port)||Service port (backend port)||Description|
|This port is used to receive requests and forward them to the real server when the CLB instance provides services.
You can configure load balancing for port 1 to 65535, such as 21 (FTP), 25 (SMTP), 80 (HTTP), and 443 (HTTPS).
|A service port provides services for CVM, receives and processes CLB traffic.
On a CLB instance, one listener port can forward traffic to multiple ports of multiple CVMs.
|On a CLB instance,
The service ports can repeat on a CLB instance. For example, both `HTTP:80` and `HTTPS:443` listeners can be bound to the same port of a CVM.