Constraints

Table 1 lists the constraints on using DNS.

**Table 1** DNS constraints
Resource	Default Quota	How to Increase
Public zone	50	Submit a service ticket.
Private zone	50
Record set	500
PTR record	50
Custom line	50
Maximum number of VPCs that can be associated with a private zone	Unlimited	-
Maximum number of VPCs that can be associated with an endpoint rule	Unlimited	-
Maximum number of resolution requests for a single ECS in a VPC	2,000 per second	For a single ECS in a VPC, the maximum number of resolution requests is 2,000 per second. If peak requests reach the limit, extra requests may not be resolved. If your services initiate an enormous volume of concurrent requests, enable DNS caching to improve lookup efficiency.
Total number of resolution requests for all ECSs in a VPC	Unlimited	-
Maximum number of recursive resolution requests for a single ECS in a VPC	600 per second	For a single ECS in a VPC, the maximum number of recursive requests is 600 per second. If peak requests reach the limit, extra requests may not be resolved. If your services initiate an enormous volume of concurrent requests, enable DNS caching to improve lookup efficiency.
Total number of recursive requests for all ECSs in a VPC	5,000 per second	For all ECSs in a VPC, the maximum number of recursive requests is 5,000 per second. If peak requests reach the limit, extra requests may not be resolved. If you have special services where access to a large number of Internet domain names is required, some domain names may not be accessed due to traffic limiting. To avoid this, submit a service ticket.