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Notes and Constraints

You can create dedicated and shared load balancers on ELB console. This section describes the quotas and restrictions that apply to ELB resources.

ELB Resource Quotas

Quotas put limits on the quantity of resources, such as the maximum number of ECSs or EVS disks that you can create.

Table 1 ELB resource quotas

Resource

Description

Default Quota

Load balancers

Load balancers per account

50

Listeners

Listeners per account

100

Forwarding policies

Forwarding policies per account

500

Backend server groups

Backend server groups per account

500

Certificates

Certificates per account

120

Backend servers

Backend servers per account

500

Listeners per load balancer

Listeners that can be added to a load balancer

50

Forwarding policies per listener

Maximum number of forwarding policies that can be added to a listener

100

Note

The quotas apply to a single account.

Other Quotas

In addition to quotas described in ELB Resource Quotas, some other resources that you can use are also limited.

You can call APIs to query quotas of the resources described in Table 2 by referring to the "Querying Quotas" section in Elastic Load Balance API Reference.

Table 2 Other quotas

Resource

Description

Default Quota

Forwarding conditions per forwarding policy

Forwarding conditions that can be added to a forwarding policy

10

Backend servers per backend server group

Backend servers that can be added to a backend server group

500

IP address group

IP address groups per load balancer

IP address groups per account

50

Listeners per IP address group

Listeners that can be associated with an IP address group

50

IP addresses per IP address group

IP addresses that can be added to an IP address group

300

Load Balancer

  • Before creating a load balancer, you must plan its region, type, protocol, and backend servers. For details, see section "Preparations for Creating a Load Balancer" in the Elastic Load Balance User Guide.
  • The maximum size of data that a load balancer can forward:
    • Layer 4 listeners: any
    • Layer 7 listeners:
      • 10 GB (file size)
      • 32 KB (the total size of the HTTP request line and HTTP request header)

Listener

  • To ensure ELB performance and simplify management, you are advised to properly plan the maximum number of listeners that can be added to a load balancer based on your service requirements. If the default quota of listeners cannot meet your requirements, you can create more load balancers.
  • The listener of a dedicated load balancer can be associated with a maximum of 50 backend server groups.
  • A certificate can be associated with a maximum of 600 listeners.
  • An HTTPS listener can have up to 30 SNI certificates.
  • Once set, the frontend protocol and port of the listener cannot be modified.

Forwarding Policy

  • Forwarding policies can be configured only for HTTP and HTTPS listeners.
  • Forwarding policies must be unique.
  • A maximum of 100 forwarding policies can be configured for a listener. If the number of forwarding policies exceeds the quota, the excess forwarding policies will not be applied.
  • Forwarding conditions:
    • If the advanced forwarding policy is not enabled, each forwarding rule has only one forwarding condition.
    • If the advanced forwarding policy is enabled, each forwarding rule has up to 10 forwarding conditions.
Table 3 Restrictions on forwarding policies

Load Balancer Type

Advanced Forwarding

Forwarding Rule

Action

Shared

Not supported

Domain name and path

Forward to another backend server group and Redirect to another listener

Dedicated

Disabled

Domain name and path

Forward to another backend server group and Redirect to another listener

Enabled

Domain name, path, HTTP request method, HTTP header, query string, cookie, and CIDR block

Forward to a backend server group, redirect to another listener, redirect to another URL, and return a specific response body.

Backend Server Group

The backend protocol of the backend server group must match the frontend protocol of the listener as described in Table 4.

Table 4 The frontend and backend protocol

Load Balancer Specification

Frontend Protocol

Backend Protocol

Network load balancing

TCP

TCP

Network load balancing

UDP

  • UDP
  • QUIC

Network load balancing

TLS

  • TLS
  • TCP

Application load balancing

HTTP

HTTP

Application load balancing

HTTPS

  • HTTP
  • HTTPS

Backend Server

  • If Transfer Client IP Address is enabled, a server cannot serve as both a backend server and a client.
  • An ECS can be added as a backend server for a maximum of 800 times. If it is added to the same backend server group, the port must be unique.

TLS Security Policy

You can create a maximum of 50 TLS security policies.

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