aws resource_error ai_generated true

Insufficient IP addresses in subnet: The subnet does not have enough free IP addresses to support the requested number of ENIs.

ID: aws/ec2-insufficient-ip-addresses

Also available as: JSON · Markdown · 中文
82%Fix Rate
86%Confidence
1Evidence
2023-09-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
EC2 API 2016-11-15 active — — —
AWS VPC CNI 1.12.0 active — — —

Root Cause

The VPC subnet has exhausted its available IP address space, preventing new ENIs or EC2 instances from launching.

generic

中文

VPC 子网已耗尽可用 IP 地址空间，阻止了新的 ENI 或 EC2 实例启动。

Official Documentation

https://docs.aws.amazon.com/vpc/latest/userguide/subnet-sizing.html

Workarounds

  1. 80% success Release unused ENIs: list ENIs with `aws ec2 describe-network-interfaces --filters Name=subnet-id,Values=subnet-xxx` and delete unattached ones with `aws ec2 delete-network-interface --network-interface-id eni-xxx`. 
    Release unused ENIs: list ENIs with `aws ec2 describe-network-interfaces --filters Name=subnet-id,Values=subnet-xxx` and delete unattached ones with `aws ec2 delete-network-interface --network-interface-id eni-xxx`.
  2. 85% success Create additional subnets in the same VPC with a larger or additional CIDR block. Add a secondary CIDR to VPC: `aws ec2 associate-vpc-cidr-block --vpc-id vpc-xxx --cidr-block 10.0.2.0/24`. Then create new subnets from the new range. 
    Create additional subnets in the same VPC with a larger or additional CIDR block. Add a secondary CIDR to VPC: `aws ec2 associate-vpc-cidr-block --vpc-id vpc-xxx --cidr-block 10.0.2.0/24`. Then create new subnets from the new range.
  3. 70% success Reduce IP consumption: use smaller EC2 instance types that require fewer ENIs, or enable 'assign public IP' only when necessary to avoid extra private IP reservation. 
    Reduce IP consumption: use smaller EC2 instance types that require fewer ENIs, or enable 'assign public IP' only when necessary to avoid extra private IP reservation.

中文步骤

  1. 释放未使用的 ENI：使用 `aws ec2 describe-network-interfaces --filters Name=subnet-id,Values=subnet-xxx` 列出 ENI，并使用 `aws ec2 delete-network-interface --network-interface-id eni-xxx` 删除未附加的 ENI。
  2. 在同一个 VPC 中创建具有更大或额外 CIDR 块的新子网。向 VPC 添加辅助 CIDR：`aws ec2 associate-vpc-cidr-block --vpc-id vpc-xxx --cidr-block 10.0.2.0/24`。然后从新范围创建新子网。
  3. 减少 IP 消耗：使用需要较少 ENI 的较小 EC2 实例类型，或仅在必要时启用“分配公有 IP”，以避免额外的私有 IP 预留。

Dead Ends

Common approaches that don't work:

  1. Delete the subnet and recreate it with a larger CIDR 70% fail

    Deleting a subnet with running resources is impossible; you must first terminate all resources.

  2. Manually assign Elastic IPs to free up private IPs 95% fail

    Elastic IPs are public IPs and don't affect private IP address usage in subnets.

  3. Increase subnet size via AWS Console (no such option) 100% fail

    Subnet CIDR size is fixed at creation; it cannot be changed afterward.