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Server Load Balancer:Limits

Last Updated:Jul 14, 2025

This topic describes the limits of Network Load Balancer (NLB), including resource quotas.

Resource quotas

Item

Default value

Increase Quota

NLB instance

Maximum number of NLB instances that each Alibaba Cloud account can have in a region

60

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the Server Load Balancer (SLB) console, click the NLB tab, and then increase the quota nlb_quota_loadbalancers_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Maximum number of elastic container instances that can be specified as backend servers for each NLB instance

1,600

Cannot be upgraded

Maximum number of Elastic Compute Service (ECS) instances, elastic network interfaces (ENIs), or IP addresses that can be specified as backend servers for each NLB instance

400

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_loadbalancer_noeci_servers_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Maximum number of listeners that can be added to each NLB instance

50

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_loadbalancer_listeners_num.

  • Go to Quota Center to request a quota increase.

For more information, see Request a quota increase.

Maximum number of additional certificates that can be added to each NLB instance, excluding the default certificate

25

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_loadbalancer_certificates_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Server group

Maximum number of NLB server groups that each Alibaba Cloud account can have in a region

3,000

Cannot upgrade

Maximum number elastic container instances that can be added to each server group

1,600

Unable to upgrade

Maximum number of ECS instances, ENIs, or IP addresses that can be added to each server group

400

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_servergroup_noeci_servers_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Maximum number of times that a backend server (including a backend server of the IP type) can be added to a server group

200

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_server_added_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Maximum number of times that each NLB server group can be associated with a listener

50

You can request a quota increase using one of the following methods:

  • Go to the Quota Management page of the SLB console, click the NLB tab, and then increase the quota nlb_quota_servergroup_attached_num.

  • Log on to the Quota Center console and request a quota increase.

For more information, see Request a quota increase.

Security policy

Maximum number of custom security policies that each Alibaba Cloud account can have in a region

50

Upgrade failed

Security group

Maximum number of security groups to which each NLB instance can be added

The number of security groups to which an NLB instance can be added and the number of security group rules that can be associated with an NLB instance are subject to the quotas of ECS security groups:

Other limits

  • When the number of backend server groups is low and a single client accesses the domain name of an NLB instance with client IP address preservation enabled, or accesses both the virtual IP addresses or EIPs of the NLB instance and a Classic Load Balancer (CLB) instance sharing the same backend servers, conflicts may occur in source IP addresses, source ports, destination IP addresses, destination ports, and transmission protocols.

  • The private virtual IP addresses to which the NLB domain name is resolved support probes. However, you need to enable ICMP when configuring Cloud Firewall or access control lists. Otherwise, the NLB domain name may fail to resolve to the virtual IP addresses because of probe failures.

  • If a UDP listener is associated with a server group that uses ID hashing algorithms other than QUIC, such as round robin and weighted round robin, the backend servers must not use stateful UDP services, such as QUIC. If the backend servers need to use stateful UDP services, we recommend using server groups with QUIC-based ID hashing.

  • If Client IP Reservation is disabled for a server group, the NLB node in each zone supports up to 60,000 concurrent connections to a single backend server (or IP address). If the number of concurrent connections exceeds this limit, NLB automatically scales its local IP addresses to prevent connection failures. The NLB node in each zone can use up to eight local IP addresses. When this limit is reached, the NLB node in each zone supports up to 250,000 concurrent connections to each backend server (or IP address). Ensure the vSwitch to which NLB is connected has sufficient available IP addresses for NLB auto-scaling.

    Note

    You can enable Client IP Reservation to avoid these circumstances. Alternatively, you can add more backend servers (or IP addresses) to the server group to distribute connections.