This topic describes how to add a UDP listener to an SLB instance. UDP is applicable to services that prioritize real-time content delivery over reliability, such as video chats and real-time quotes. You can add a UDP listener to forward UDP requests.
Prerequisites
An SLB instance is created. For more information, see Create an SLB instance.
Background information
- Ports 250, 4789, and 4790 of a UDP listener are reserved and therefore are unavailable for your configuration.
- Fragmented packets are not supported.
- The UDP listeners of an SLB instance in a classic network do not support the viewing of source IP addresses.
- The following operations take five minutes to take effect if they are performed for
a UDP listener:
- Remove backend servers
- Set the weight of a backend server to 0 after it is detected unhealthy
- IPv6 addresses have longer IP headers than IPv4 addresses. When you create a UDP listener
for an IPv6 SLB instance, make sure that the maximum transmission unit (MTU) size
of the network interface controller (NIC) on each backend server (ECS instance in
most cases) that communicates with the SLB instance is not greater than 1,200 bytes.
Otherwise, oversized packets may be discarded. The configuration files of some applications
need to be modified based on the MTU size.
If you use a TCP, HTTP, or HTTPS listener, you do not need to perform additional configuration steps because TCP supports automatic maximum segment size (MSS) adjustment.
Step 1: Start the listener configuration wizard
To start the listener configuration wizard, perform the following operations:
Step 2: Configure the UDP listener
To configure the UDP listener, perform the following operations:
Step 3: Add backend servers
After you configure the listener, you must add backend servers to process client requests. You can add backend servers to the default server group, or create VServer groups or primary/secondary server groups and then add servers to them. For more information, see Backend server overview.
This example adds backend servers to the default server group.
Step 4: Configure the health check
SLB checks the availability of backend servers by performing the health check. The health check feature improves the availability of frontend services by minimizing downtime caused by health issues of backend servers. Click Modify to configure advanced health check settings. For more information, see Health check overview.
Click Next.
Step 5: Confirm the settings
Complete the following steps to confirm and apply the listener settings: