amazon-vpc-cni-k8s

Networking plugin for pod networking in Kubernetes using Elastic Network Interfaces on AWS.

Setup

Download the latest version of the yaml and apply it to the cluster.

kubectl apply -f aws-k8s-cni.yaml

Launch kubelet with network plugins set to cni (--network-plugin=cni), the cni directories configured (--cni-config-dir and --cni-bin-dir) and node ip set to the primary IPv4 address of the primary ENI for the instance (--node-ip=$(curl http://169.254.169.254/latest/meta-data/local-ipv4)). It is also recommended that you set --max-pods equal to (the number of ENIs for the instance type × (the number of IPs per ENI - 1)) + 2; for details, see vpc_ip_resource_limit.go. Setting --max-pods will prevent scheduling that exceeds the IP address resources available to the kubelet.

The default manifest expects --cni-conf-dir=/etc/cni/net.d and --cni-bin-dir=/opt/cni/bin.

Alternatively there is also a Helm chart: eks/aws-vpc-cni

IAM Policy

See here for required IAM policies.

Building

• make defaults to make build-linux that builds the Linux binaries.
• unit-test, format,lint and vet provide ways to run the respective tests/tools and should be run before submitting a PR.
• make docker will create a docker container using docker buildx that contains the finished binaries, with a tag of amazon/amazon-k8s-cni:latest
• make docker-unit-tests uses a docker container to run all unit tests.
• Builds for all build and test actions run in docker containers based on .go-version unless a different GOLANG_IMAGE tag is passed in.

Components

There are 2 components:

• CNI Plugin, which will wire up the host's and pod's network stack when called.
• ipamd, a long-running node-Local IP Address Management (IPAM) daemon, is responsible for:
  • maintaining a warm-pool of available IP addresses, and
  • assigning an IP address to a Pod.

The details can be found in Proposal: CNI plugin for Kubernetes networking over AWS VPC.

Help & Feedback

For help, please consider the following venues (in order):

• Amazon EKS Best Practices Guide for Networking
• Troubleshooting Guide provides tips on how to debug and troubleshoot this CNI.
• Search open issues
• File an issue
• Chat with us on the #aws-vpc-cni channel in the Kubernetes Slack community.

Recommended Version

For all Kubernetes releases, we recommend installing the latest VPC CNI release. The following table denotes our oldest recommended VPC CNI version for each actively supported Kubernetes release.

Kubernetes Release	1.29	1.28	1.27	1.26	1.25	1.24
VPC CNI Version	v1.14.1+	v1.13.4+	v1.12.5+	v1.12.0+	v1.11.4+	v1.9.3+

Version Upgrade

Upgrading (or downgrading) the VPC CNI version should result in no downtime. Existing pods should not be affected and will not lose network connectivity. New pods will be in pending state until the VPC CNI is fully initialized and can assign pod IP addresses. In v1.12.0+, VPC CNI state is restored via an on-disk file: /var/run/aws-node/ipam.json. In lower versions, state is restored via calls to container runtime.

ENI Allocation

When a worker node first joins the cluster, there is only 1 ENI along with all of the addresses on the ENI. Without any configuration, ipamd always tries to keep one extra ENI.

When the number of pods running on the node exceeds the number of addresses on a single ENI, the CNI backend starts allocating a new ENI using the following allocation scheme:

• If the number of current running Pods is between 0 and 29, ipamd will allocate one more eni. And Warm-Pool size is 2 eni * (30 -1) = 58
• If the number of current running Pods is between 30 and 58, ipamd will allocate 2 more eni. And Warm-Pool size is 3 eni * (30 -1) = 87

For example, a m4.4xlarge node can have up to 8 ENIs, and each ENI can have up to 30 IP addresses. See Elastic Network Interfaces documentation for details.

For a detailed explanation, see WARM_ENI_TARGET, WARM_IP_TARGET and MINIMUM_IP_TARGET.

Privileged mode

VPC CNI makes use of privileged mode (privileged: true) in the manifest for its aws-vpc-cni-init and aws-eks-nodeagent containers. aws-vpc-cni-init container requires elevated privilege to set the networking kernel parameters while aws-eks-nodeagent container requires these privileges for attaching BPF probes to enforce network policy

Network Policies

In Kubernetes, by default, all pod-to-pod communication is allowed. Communication can be restricted with Kubernetes NetworkPolicy objects.

VPC CNI versions v1.14, and greater support Kubernetes Network Policies.. Network Policies specify how pods can communicate over the network, at the IP address or port level. The VPC CNI implements the Kubernetes NetworkPolicy API. Network policies generally include a pod selector, and Ingress/Egress rules.

For EKS clusters, review Configure your cluster for Kubernetes network policies in the Amazon EKS User Guide.

The AWS VPC CNI implementation of network policies may be enabled in self-managed clusters. This requires the VPC CNI agent, the Network Policy Controller, and Network Policy Node Agent.

Review the Network Policy FAQ for more information.

Network Policy Related Components

• Network Policy Controller watches for NetworkPolicy objects and instructs the node agent.
  • Network policy controller configures policies for pods in parallel to pod provisioning, until then new pods will come up with default allow policy. All ingress and egress traffic is allowed to and from the new pods until they are resolved against the existing policies.
  • This controller is automatically installed on the EKS Control Plane.
• Network Policy Node Agent implements Network Policies on nodes by creating eBPF programs.
• AWS eBPF SDK for Go provides an interface to interact with eBPF programs on the node. This SDK allows for runtime introspection, tracing, and analysis of eBPF execution, aiding in identifying and resolving connectivity issues.
• VPC Resource Controller manages Branch & Trunk Network Interfaces for Kubernetes Pods.

ConfigMap

If the VPC CNI is installed as an Amazon EKS add-ons (also known as a managed add-on), configure it using AWS APIs as described in the EKS User Guide.

If the VPC CNI is installed with a Helm Chart, the ConfigMap is installed in your cluster. Review the Helm Chart information.

Otherwise, the VPC CNI may be configured with a ConfigMap, as shown below:

apiVersion: v1
kind: ConfigMap
metadata:
  name: amazon-vpc-cni
  namespace: kube-system
data:
  enable-network-policy-controller: "true"

• enable-network-policy-controller
  • Default: False
  • If enabled, the VPC CNI will enforce NetworkPolicies. Pods that are selected by at least one NetworkPolicy will have their traffic restricted.

Helm Charts

AWS publishes a Helm chart to install the VPC CNI. Review how to install the helm chart, and the configuration parameters for the chart.

CNI Configuration Variables

The Amazon VPC CNI plugin for Kubernetes supports a number of configuration options, which are set through environment variables. The following environment variables are available, and all of them are optional.

AWS_MANAGE_ENIS_NON_SCHEDULABLE (v1.12.6+)

Type: Boolean as a String

Default: false

Specifies whether IPAMD should allocate or deallocate ENIs on a non-schedulable node.

AWS_VPC_CNI_NODE_PORT_SUPPORT

Type: Boolean as a String

Default: true

Specifies whether NodePort services are enabled on a worker node's primary network interface. This requires additional iptables rules, and the kernel's reverse path filter on the primary interface is set to loose.

AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG

Type: Boolean as a String

Default: false

Specifies that your pods may use subnets and security groups that are independent of your worker node's VPC configuration. By default, pods share the same subnet and security groups as the worker node's primary interface. Setting this variable to true causes ipamd to use the security groups and VPC subnet in a worker node's ENIConfig for elastic network interface allocation. You must create an ENIConfig custom resource for each subnet that your pods will reside in, and then annotate or label each worker node to use a specific ENIConfig. Multiple worker nodes can be annotated or labelled with the same ENIConfig, but each Worker node can be annotated with a single ENIConfig at a time. Further, the subnet in the ENIConfig must belong to the same Availability Zone that the worker node resides in. For more information, see CNI Custom Networking in the Amazon EKS User Guide.

ENI_CONFIG_ANNOTATION_DEF

Type: String

Default: k8s.amazonaws.com/eniConfig

Specifies node annotation key name. This should be used when AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG=true. Annotation value will be used to set ENIConfig name. Note that annotations take precedence over labels.

ENI_CONFIG_LABEL_DEF

Type: String

Default: k8s.amazonaws.com/eniConfig

Specifies node label key name. This should be used when AWS_VPC_K8S_CNI_CUSTOM_NETWORK_CFG=true. Label value will be used to set ENIConfig name. Note that annotations will take precedence over labels. To use labels, ensure there is no annotation with key k8s.amazonaws.com/eniConfig or defined key (in ENI_CONFIG_ANNOTATION_DEF) set on the node. To select an ENIConfig based upon availability zone set this to topology.kubernetes.io/zone and create an ENIConfig custom resource for each availability zone (e.g. us-east-1a). Note that tag failure-domain.beta.kubernetes.io/zone is deprecated and replaced with the tag topology.kubernetes.io/zone.

HOST_CNI_BIN_PATH

Type: String

Default: /host/opt/cni/bin

Specifies the location to install CNI binaries. Note that the aws-node daemonset mounts /opt/cni/bin to /host/opt/cni/bin. The value you choose must be a location that the aws-node pod can write to.

HOST_CNI_CONFDIR_PATH

Type: String

Default: /host/etc/cni/net.d

Specifies the location to install the VPC CNI conflist. Note that the aws-node daemonset mounts /etc/cni/net.d to /host/etc/cni/net.d. The value you choose must be a location that the aws-node pod can write to.

AWS_VPC_ENI_MTU (v1.6.0+)

Type: Integer as a String

Default: 9001

Used to configure the MTU size for attached ENIs. The valid range for IPv4 is from 576 to 9001, while the valid range for IPv6 is from 1280 to 9001.

AWS_VPC_K8S_CNI_EXTERNALSNAT

Type: Boolean as a String

Default: false

Specifies whether an external NAT gateway should be used to provide SNAT of secondary ENI IP addresses. If set to true, the SNAT iptables rule and off-VPC IP rule are not applied, and these rules are removed if they have already been applied. Disable SNAT if you need to allow inbound communication to your pods from external VPNs, direct connections, and external VPCs, and your pods do not need to access the Internet directly via an Internet Gateway. However, your nodes must be running in a private subnet and connected to the internet through an AWS NAT Gateway or another external NAT device.

AWS_VPC_K8S_CNI_RANDOMIZESNAT

Type: String

Default: prng

Valid Values: hashrandom, prng, none

Specifies whether the SNAT iptables rule should randomize the outgoing ports for connections. This setting takes effect when AWS_VPC_K8S_CNI_EXTERNALSNAT=false, which is the default setting. The default setting for AWS_VPC_K8S_CNI_RANDOMIZESNAT is prng, meaning that --random-fully will be added to the SNAT iptables rule. For old versions of iptables that do not support --random-fully this option will fall back to --random. To disable random port allocation, if you for example rely on sequential port allocation for outgoing connections set it to none.

Note: Any options other than none will cause outbound connections to be assigned a source port that is not necessarily part of the ephemeral port range set at the OS level (/proc/sys/net/ipv4/ip_local_port_range). This is relevant for any customers that might have NACLs restricting traffic based on the port range found in ip_local_port_range.

AWS_VPC_K8S_CNI_EXCLUDE_SNAT_CIDRS (v1.6.0+)

Type: String

Default: empty

Specify a comma-separated list of IPv4 CIDRs to exclude from SNAT. For every item in the list an iptables rule and off-VPC IP rule will be applied. If an item is not a valid ipv4 range it will be skipped. This should be used when AWS_VPC_K8S_CNI_EXTERNALSNAT=false.

POD_MTU (v1.16.4+)

Type: Integer as a String

Note: If unset, the default value is derived from AWS_VPC_ENI_MTU, which defaults to 9001. Default: 9001

Used to configure the MTU size for pod virtual interfaces. The valid range for IPv4 is from 576 to 9001, while the valid range for IPv6 is from 1280 to 9001.

WARM_ENI_TARGET

Type: Integer as a String

Default: 1

Specifies the number of free elastic network interfaces (and all of their available IP addresses) that the ipamd daemon should attempt to keep available for pod assignment on the node. By default, ipamd attempts to keep 1 elastic network interface and all of its IP addresses available for pod assignment. The number of IP addresses per network interface varies by instance type. For more information, see IP Addresses Per Network Interface Per Instance Type in the Amazon EC2 User Guide for Linux Instances.

For example, an m4.4xlarge launches with 1 network interface and 30 IP addresses. If 5 pods are placed on the node and 5 free IP addresses are removed from the IP address warm pool, then ipamd attempts to allocate more interfaces until WARM_ENI_TARGET free interfaces are available on the node.

NOTE! If WARM_IP_TARGET is set, then this environment variable is ignored and the WARM_IP_TARGET behavior is used instead.

WARM_IP_TARGET

Type: Integer

Default: None

Specifies the number of free IP addresses that the ipamd daemon should attempt to keep available for pod assignment on the node. Setting this to a non-positive value is the same as setting this to 0 or not setting the variable. With ENABLE_PREFIX_DELEGATION set to true then ipamd daemon will check if the existing (/28) prefixes are enough to maintain the WARM_IP_TARGET if it is not sufficient then more prefixes will be attached.

For example,

1. if WARM_IP_TARGET is set to 5, then ipamd attempts to keep 5 free IP addresses available at all times. If the elastic network interfaces on the node are unable to provide these free addresses, ipamd attempts to allocate more interfaces until WARM_IP_TARGET free IP addresses are available.
2. ENABLE_PREFIX_DELEGATION set to true and WARM_IP_TARGET is 16. Initially, 1 (/28) prefix is sufficient but once a single pod is assigned IP then remaining free IPs are 15 hence IPAMD will allocate 1 more prefix to achieve 16 WARM_IP_TARGET

NOTE! Avoid this setting for large clusters, or if the cluster has high pod churn. Setting it will cause additional calls to the EC2 API and that might cause throttling of the requests. It is strongly suggested to set MINIMUM_IP_TARGET when using WARM_IP_TARGET.

If both WARM_IP_TARGET and MINIMUM_IP_TARGET are set, ipamd will attempt to meet both constraints. This environment variable overrides WARM_ENI_TARGET behavior. For a detailed explanation, see WARM_ENI_TARGET, WARM_IP_TARGET and MINIMUM_IP_TARGET.

If ENABLE_PREFIX_DELEGATION set to true and WARM_IP_TARGET overrides WARM_PREFIX_TARGET behavior. For a detailed explanation, see WARM_PREFIX_TARGET, WARM_IP_TARGET and MINIMUM_IP_TARGET.

MINIMUM_IP_TARGET (v1.6.0+)

Type: Integer

Default: None

Specifies the number of total IP addresses that the ipamd daemon should attempt to allocate for pod assignment on the node. MINIMUM_IP_TARGET behaves identically to WARM_IP_TARGET except that instead of setting a target number of free IP addresses to keep available at all times, it sets a target number for a floor on how many total IP addresses are allocated. Setting to a non-positive value is same as setting this to 0 or not setting the variable.

MINIMUM_IP_TARGET is for pre-scaling, WARM_IP_TARGET is for dynamic scaling. For example, suppose a cluster has an expected pod density of approximately 30 pods per node. If WARM_IP_TARGET is set to 30 to ensure there are enough IPs allocated up front by the CNI, then 30 pods are deployed to the node, the CNI will allocate an additional 30 IPs, for a total of 60, accelerating IP exhaustion in the relevant subnets. If instead MINIMUM_IP_TARGET is set to 30 and WARM_IP_TARGET to 2, after the 30 pods are deployed the CNI would allocate an additional 2 IPs. This still provides elasticity, but uses roughly half as many IPs as using WARM_IP_TARGET alone (32 IPs vs 60 IPs).

This also improves the reliability of the EKS cluster by reducing the number of calls necessary to allocate or deallocate private IPs, which may be throttled, especially at scaling-related times.

NOTE!

1. If MINIMUM_IP_TARGET is set, WARM_ENI_TARGET will be ignored. Please utilize WARM_IP_TARGET instead.
2. If MINIMUM_IP_TARGET is set and WARM_IP_TARGET is not set, WARM_IP_TARGET is assumed to be 0, which leads to the number of IPs attached to the node will be the value of MINIMUM_IP_TARGET. This configuration will prevent future ENIs/IPs from being allocated. It is strongly recommended that WARM_IP_TARGET should be set greater than 0 when MINIMUM_IP_TARGET is set.

MAX_ENI

Type: Integer

Default: None

Specifies the maximum number of ENIs that will be attached to the node. When MAX_ENI is unset or 0 (or lower), the setting is not used, and the maximum number of ENIs is always equal to the maximum number for the instance type in question. Even when MAX_ENI is a positive number, it is limited by the maximum number for the instance type.

AWS_VPC_K8S_CNI_LOGLEVEL

Type: String

Default: DEBUG

Valid Values: DEBUG, INFO, WARN, ERROR, FATAL. (Not case sensitive)

Specifies the log level for ipamd and cni-metric-helper.

AWS_VPC_K8S_CNI_LOG_FILE

Type: String

Default: /host/var/log/aws-routed-eni/ipamd.log

Valid Values: stdout, stderr, or a file path

Specifies where to write the logging output of ipamd: stdout, stderr, or a file path other than the default (/var/log/aws-routed-eni/ipamd.log).

Note: /host/var/log/... is the container file-system path, which maps to /var/log/... on the node.

Note: The IPAMD process runs within the aws-node pod, so writing to stdout or stderr will write to aws-node pod logs.

AWS_VPC_K8S_PLUGIN_LOG_FILE

Type: String

Default: /var/log/aws-routed-eni/plugin.log

Valid Values: stderr or a file path. Note that setting to the empty string is an alias for stderr, and this comes from upstream kubernetes best practices.

Specifies where to write the logging output for aws-cni plugin: stderr or a file path other than the default (/var/log/aws-routed-eni/plugin.log).

Note: stdout cannot be supported for plugin log. Please refer to #1248 for more details.

Note: In EKS 1.24+, the CNI plugin is exec'ed by the container runtime, so stderr is for the container-runtime process, NOT the aws-node pod. In older versions, the CNI plugin was exec'ed by kubelet, so stderr is for the kubelet process.

Note: If chaining an external plugin (i.e. Cilium) that does not provide a pluginLogFile in its config file, the CNI plugin will by default write to os.Stderr.

AWS_VPC_K8S_PLUGIN_LOG_LEVEL

Type: String

Default: DEBUG

Valid Values: DEBUG, INFO, WARN, ERROR, FATAL. (Not case sensitive)

Specifies the loglevel for aws-cni plugin.

INTROSPECTION_BIND_ADDRESS

Type: String

Default: 127.0.0.1:61679

Specifies the bind address for the introspection endpoint.

A Unix Domain Socket can be specified with the unix: prefix before the socket path.

DISABLE_INTROSPECTION

Type: Boolean as a String

Default: false

Specifies whether introspection endpoints are disabled on a worker node. Setting this to true will reduce the debugging information we can get from the node when running the aws-cni-support.sh script.

DISABLE_METRICS

Type: Boolean as a String

Default: false

Specifies whether the prometheus metrics endpoint is disabled or not for ipamd. By default metrics are published on :61678/metrics.

AWS_VPC_K8S_CNI_VETHPREFIX

Type: String

Default: eni

Specifies the veth prefix used to generate the host-side veth device name for the CNI. The prefix can be at most 4 characters long. The prefixes eth, vlan, and lo are reserved by the CNI plugin and cannot be specified. We recommend using prefix name not shared by any other network interfaces on the worker node instance.

ADDITIONAL_ENI_TAGS (v1.6.0+)

Type: String

Default: {}

Example values: {"tag_key": "tag_val"}

Metadata applied to ENI helps you categorize and organize your resources for billing or other purposes. Each tag consists of a custom-defined key and an optional value. Tag keys can have a maximum character length of 128 characters. Tag values can have a maximum length of 256 characters. These tags will be added to all ENIs on the host.

Important: Custom tags should not contain k8s.amazonaws.com prefix as it is reserved. If the tag has k8s.amazonaws.com string, tag addition will be ignored.

AWS_VPC_K8S_CNI_CONFIGURE_RPFILTER (deprecated v1.12.1+)

Type: Boolean as a String

Default: true

Specifies whether ipamd should configure rp filter for primary interface. Setting this to false will require rp filter to be configured through init container.

NOTE! AWS_VPC_K8S_CNI_CONFIGURE_RPFILTER has been deprecated, so setting this environment variable results in a no-op. The init container unconditionally configures the rp filter for the primary interface.

CLUSTER_NAME

Type: String

Default: ""

Specifies the cluster name to tag allocated ENIs with. See the "Cluster Name tag" section below.

CLUSTER_ENDPOINT (v1.12.1+)

Type: String

Default: ""

Specifies the cluster endpoint to use for connecting to the api-server without relying on kube-proxy. This is an optional configuration parameter that can improve the initialization time of the AWS VPC CNI.

NOTE! When setting CLUSTER_ENDPOINT, it is STRONGLY RECOMMENDED that you enable private endpoint access for your API server, otherwise VPC CNI requests can traverse the public NAT gateway and may result in additional charges.

ENABLE_POD_ENI (v1.7.0+)

Type: Boolean as a String

Default: false

To enable security groups for pods you need to have at least an EKS 1.17 eks.3 cluster.

Setting ENABLE_POD_ENI to true will allow IPAMD to add the vpc.amazonaws.com/has-trunk-attached label to the node if the instance has the capacity to attach an additional ENI.

The label notifies vpc-resource-controller to attach a Trunk ENI to the instance. The label value is initially set to false and is marked to true by IPAMD when vpc-resource-controller attaches a Trunk ENI to the instance. However, there might be cases where the label value will remain false if the instance doesn't support ENI Trunking.

Once enabled the VPC resource controller will then advertise branch network interfaces as extended resources on these nodes in your cluster. Branch interface capacity is additive to existing instance type limits for secondary IP addresses and prefixes. For example, a c5.4xlarge can continue to have up to 234 secondary IP addresses or 234 /28 prefixes assigned to standard network interfaces and up to 54 branch network interfaces. Each branch network interface only receives a single primary IP address and this IP address will be allocated to pods with a security group(branch ENI pods).

Any of the WARM targets do not impact the scale of the branch ENI pods so you will have to set the WARM_{ENI/IP/PREFIX}_TARGET based on the number of non-branch ENI pods. If you are having the cluster mostly using pods with a security group consider setting WARM_IP_TARGET to a very low value instead of default WARM_ENI_TARGET or WARM_PREFIX_TARGET to reduce wastage of IPs/ENIs.

NOTE! Toggling ENABLE_POD_ENI from true to false will not detach the Trunk ENI from an instance. To delete/detach the Trunk ENI from an instance, you need to recycle the instance.

POD_SECURITY_GROUP_ENFORCING_MODE (v1.11.0+)

Type: String

Default: strict

Valid Values: strict, standard

Once ENABLE_POD_ENI is set to true, this value controls how the traffic of pods with the security group behaves.

• strict mode: all inbound/outbound traffic from pod with security group will be enforced by security group rules. This is the default mode if POD_SECURITY_GROUP_ENFORCING_MODE is not set.

• standard mode: the traffic of pod with security group behaves same as pods without a security group, except that each pod occupies a dedicated branch ENI.

  • inbound traffic to pod with security group from another host will be enforced by security group rules.
  • outbound traffic from pod with security group to another host in the same VPC will be enforced by security group rules.
  • inbound/outbound traffic from another pod on the same host or another service on the same host(such as kubelet/nodeLocalDNS) won't be enforced by security group rules.
  • outbound traffic from pod with security group to IP address outside VPC
    • if externalSNAT enabled, traffic won't be SNATed, thus will be enforced by security group rules.
    • if externalSNAT disabled, traffic will be SNATed via eth0, thus will only be enforced by the security group associated with eth0.

NOTE!: To make new behavior be in effect after switching the mode, existing pods with security group must be recycled. Alternatively, you can restart the nodes as well.

DISABLE_TCP_EARLY_DEMUX (v1.7.3+)

Type: Boolean as a String

Default: false

If ENABLE_POD_ENI is set to true, for the kubelet to connect via TCP (for liveness or readiness probes) to pods that are using per pod security groups, DISABLE_TCP_EARLY_DEMUX should be set to true for amazon-k8s-cni-init the container under initcontainers. This will increase the local TCP connection latency slightly. Details on why this is needed can be found in this #1212 comment. To use this setting, a Linux kernel version of at least 4.6 is needed on the worker node.

You can use the below command to enable DISABLE_TCP_EARLY_DEMUX to true -

kubectl patch daemonset aws-node -n kube-system -p '{"spec": {"template": {"spec": {"initContainers": [{"env":[{"name":"DISABLE_TCP_EARLY_DEMUX","value":"true"}],"name":"aws-vpc-cni-init"}]}}}}'

ENABLE_SUBNET_DISCOVERY (v1.18.0+)

Type: Boolean as a String

Default: true

Subnet discovery is enabled by default. VPC-CNI will pick the subnet with the most number of free IPs from the nodes' VPC/AZ to create the secondary ENIs. The subnets considered are the subnet the node is created in and subnets tagged with kubernetes.io/role/cni. If ENABLE_SUBNET_DISCOVERY is set to false or if DescribeSubnets fails due to IAM permissions, all secondary ENIs will be created in the subnet the node is created in.

ENABLE_PREFIX_DELEGATION (v1.9.0+)

Type: Boolean as a String

Default: false

To enable prefix delegation on nitro instances. Setting ENABLE_PREFIX_DELEGATION to true will start allocating a prefix (/28 for IPv4 and /80 for IPv6) instead of a secondary IP in the ENIs subnet. The total number of prefixes and private IP addresses will be less than the limit on private IPs allowed by your instance. Setting or resetting of ENABLE_PREFIX_DELEGATION while pods are running or if ENIs are attached is supported and the new pods allocated will get IPs based on the mode of IPAMD but the max pods of kubelet should be updated which would need either kubelet restart or node recycle.

Setting ENABLE_PREFIX_DELEGATION to true will not increase the density of branch ENI pods. The limit on the number of branch network interfaces per instance type will remain the same. Each branch network will be allocated a primary IP and this IP will be allocated for the branch ENI pods.

Please refer to VPC CNI Feature Matrix section below for additional information around using Prefix delegation with Custom Networking and Security Groups Per Pod features.

Note: ENABLE_PREFIX_DELEGATION needs to be set to true when VPC CNI is configured to operate in IPv6 mode (supported in v1.10.0+). Prefix Delegation in IPv4 and IPv6 modes is supported on Nitro based Bare Metal instances as well from v1.11+. If you're using Prefix Delegation feature on Bare Metal instances, downgrading to an earlier version of VPC CNI from v1.11+ will be disruptive and not supported.

WARM_PREFIX_TARGET (v1.9.0+)

Type: Integer

Default: None

Specifies the number of free IPv4(/28) prefixes that the ipamd daemon should attempt to keep available for pod assignment on the node. Setting to a non-positive value is same as setting this to 0 or not setting the variable. This environment variable works when ENABLE_PREFIX_DELEGATION is set to true and is overridden when WARM_IP_TARGET and MINIMUM_IP_TARGET are configured.

DISABLE_NETWORK_RESOURCE_PROVISIONING (v1.9.1+)

Type: Boolean as a String

Default: false

Setting DISABLE_NETWORK_RESOURCE_PROVISIONING to true will make IPAMD depend only on IMDS to get attached ENIs and IPs/prefixes.

ENABLE_BANDWIDTH_PLUGIN (v1.10.0+)

Type: Boolean as a String

Default: false

Setting ENABLE_BANDWIDTH_PLUGIN to true will update 10-aws.conflist to include upstream bandwidth plugin as a chained plugin.

NOTE: Kubernetes Network Policy is supported in Amazon VPC CNI starting with version v1.14.0. Note that bandwidth plugin is not compatible with Amazon VPC CNI based Network policy. Network Policy agent uses TC (traffic classifier) system to enforce configured network policies for the pods. The policy enforcement will fail if bandwidth plugin is enabled due to conflict between TC configuration of bandwidth plugin and Network policy agent. We're exploring options to support bandwidth plugin along with Network policy feature and the issue is tracked here

ANNOTATE_POD_IP (v1.9.3+)

Type: Boolean as a String

Default: false

Setting ANNOTATE_POD_IP to true will allow IPAMD to add an annotation vpc.amazonaws.com/pod-ips to the pod with pod IP.

There is a known issue with kubelet taking time to update Pod.Status.PodIP leading to calico being blocked on programming the policy. Setting ANNOTATE_POD_IP to true will enable AWS VPC CNI plugin to add Pod IP as an annotation to the pod spec to address this race condition.

To annotate the pod with pod IP, you will have to add patch permission for pods resource in aws-node clusterrole. You can use the below command -

cat << EOF > append.yaml
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - patch
EOF

kubectl apply -f <(cat <(kubectl get clusterrole aws-node -o yaml) append.yaml)

NOTE: Adding patch permissions to the aws-node Daemonset increases the security scope for the plugin, so add this permission only after performing a proper security assessment of the tradeoffs.

ENABLE_IPv4 (v1.10.0+)

Type: Boolean as a String

Default: true

VPC CNI can operate in either IPv4 or IPv6 mode. Setting ENABLE_IPv4 to true will configure it in IPv4 mode (default mode).

Note: Dual-stack mode isn't yet supported. So, enabling both IPv4 and IPv6 will be treated as an invalid configuration.

ENABLE_IPv6 (v1.10.0+)

Type: Boolean as a String

Default: false

VPC CNI can operate in either IPv4 or IPv6 mode. Setting ENABLE_IPv6 to true (both under aws-node and aws-vpc-cni-init containers in the manifest) will configure it in IPv6 mode. IPv6 is only supported in Prefix Delegation mode, so ENABLE_PREFIX_DELEGATION needs to be set to true if VPC CNI is configured to operate in IPv6 mode. Prefix delegation is only supported on nitro instances.

Note: Please make sure that the required IPv6 IAM policy is applied (Refer to IAM Policy section above). Dual stack mode isn't yet supported. So, enabling both IPv4 and IPv6 will be treated as invalid configuration. Please refer to the VPC CNI Feature Matrix section below for additional information.

ENABLE_NFTABLES (introduced in v1.12.1, deprecated in v1.13.2+)

Type: Boolean as a String

Default: false

VPC CNI uses iptables-legacy by default. Setting ENABLE_NFTABLES to true will update VPC CNI to use iptables-nft.

Note: VPC CNI image contains iptables-legacy and iptables-nft. Switching between them is done via update-alternatives. It is strongly recommended that the iptables mode matches that which is used by the base OS and kube-proxy. Switching modes while pods are running or rules are installed will not trigger reconciliation. It is recommended that rules are manually updated or nodes are drained and cordoned before updating. If reloading node, ensure that previous rules are not set to be persisted.

AWS_EXTERNAL_SERVICE_CIDRS (v1.12.6+)

Type: String

Default: empty

Specify a comma-separated list of IPv4 CIDRs that must be routed via main routing table. This is required for secondary ENIs to reach endpoints outside of VPC that are backed by a service. For every item in the list, an ip rule will be created with a priority greater than the ip rule capturing egress traffic from the container. If an item is not a valid IPv4 CIDR, it will be skipped.

AWS_EC2_ENDPOINT (v1.13.0+)

Type: String

Default: empty

Specify the EC2 endpoint to use. This is useful if you are using a custom endpoint for EC2. For example, if you are using a proxy for EC2, you can set this to the proxy endpoint. Any kind of URL or IP address is valid such as https://localhost:8080 or http://ec2.us-west-2.customaws.com. If this is not set, the default EC2 endpoint will be used.

DISABLE_LEAKED_ENI_CLEANUP (v1.13.0+)

Type: Boolean as a String

Default: false

On IPv4 clusters, IPAMD schedules an hourly background task per node that cleans up leaked ENIs. Setting this environment variable to true disables that job. The primary motivation to disable this task is to decrease the amount of EC2 API calls made from each node. Note that disabling this task should be considered carefully, as it requires users to manually cleanup ENIs leaked in their account. See #1223 for a related discussion.

ENABLE_V6_EGRESS (v1.13.0+)

Type: Boolean as a String

Default: false

Specifies whether PODs in an IPv4 cluster support IPv6 egress. If env is set to true, range fd00::ac:00/118 is reserved for IPv6 egress.

This environment variable must be set for both the aws-vpc-cni-init and aws-node containers in order for this feature to work properly. This feature also requires that the node has an IPv6 address assigned to its primary ENI, as this address is used for SNAT to IPv6 endpoints outside of the cluster. If the configuration prerequisites are not met, the egress-cni plugin is not enabled and an error log is printed in the aws-node container.

Note that enabling/disabling this feature only affects whether newly created pods have an IPv6 interface created. Therefore, it is recommended that you reboot existing nodes after enabling/disabling this feature.

The value set in POD_MTU / AWS_VPC_ENI_MTU is used to configure the MTU size of egress interface.

ENABLE_V4_EGRESS (v1.15.1+)

Type: Boolean as a String

Default: true

Specifies whether PODs in an IPv6 cluster support IPv4 egress. If env is set to true, range 169.254.172.0/22 is reserved for IPv4 egress. When enabled, traffic egressing an IPv6 pod destined to an IPv4 endpoint will be SNAT'ed via the node IPv4 address.

Note that enabling/disabling this feature only affects whether newly created pods have an IPv4 interface created. Therefore, it is recommended that you reboot existing nodes after enabling/disabling this feature.

The value set in POD_MTU / AWS_VPC_ENI_MTU is used to configure the MTU size of egress interface.

IP_COOLDOWN_PERIOD (v1.15.0+)

Type: Integer as a String

Default: 30

Specifies the number of seconds an IP address is in cooldown after pod deletion. The cooldown period gives network proxies, such as kube-proxy, time to update node iptables rules when the IP was registered as a valid endpoint, such as for a service. Modify this value with caution, as kube-proxy update time scales with the number of nodes and services.

Note: 0 is a supported value, however it is highly discouraged. Note: Higher cooldown periods may lead to a higher number of EC2 API calls as IPs are in cooldown cache.

DISABLE_POD_V6 (v1.15.0+)

Type: Boolean as a String

Default: false

When DISABLE_POD_V6 is set, the tuning plugin is chained and configured to disable IPv6 networking in each newly created pod network namespace. Set this variable when you have an IPv4 cluster and containerized applications that cannot tolerate IPv6 being enabled. Container runtimes such as containerd will enable IPv6 in newly created container network namespaces regardless of host settings.

Note that if you set this while using Multus, you must ensure that any chained plugins do not depend on IPv6 networking. You must also ensure that chained plugins do not also modify these sysctls.

NETWORK_POLICY_ENFORCING_MODE (v1.17.1+)

Type: String

Default: standard

Network Policy agent now supports two modes for Network Policy enforcement - Strict and Standard. By default, the Amazon VPC CNI plugin for Kubernetes configures network policies for pods in parallel with the pod provisioning. In the standard mode, until all of the policies are configured for the new pod, containers in the new pod will start with a default allow policy. A default allow policy means that all ingress and egress traffic is allowed to and from the new pods. However, in the strict mode, a new pod will be blocked from Egress and Ingress connections till a qualifying Network Policy is applied. In Strict Mode, you must have a network policy defined for every pod in your cluster. Host Networking pods are exempted from this requirement.

VPC CNI Feature Matrix

IP Mode	Secondary IP Mode	Prefix Delegation	Security Groups Per Pod	WARM & MIN IP/Prefix Targets	External SNAT	Network Policies
IPv4	Yes	Yes	Yes	Yes	Yes	Yes
IPv6	No	Yes	No	No	No	Yes

ENI tags related to Allocation

This plugin interacts with the following tags on ENIs:

• cluster.k8s.amazonaws.com/name
• kubernetes.io/role/cni
• node.k8s.amazonaws.com/instance_id
• node.k8s.amazonaws.com/no_manage

Cluster Name tag

The tag cluster.k8s.amazonaws.com/name will be set to the cluster name of the aws-node daemonset which created the ENI.

CNI role tag

The tag kubernetes.io/role/cni is read by the aws-node daemonset to determine if a secondary subnet can be used for creating secondary ENIs.

This tag is not set by the cni plugin itself, but rather must be set by a user to indicate that a subnet can be used for secondary ENIs. Secondary subnets to be used must have this tag. The primary subnet (node's subnet) is not required to be tagged.

Instance ID tag

The tag node.k8s.amazonaws.com/instance_id will be set to the instance ID of the aws-node instance that allocated this ENI.

No Manage tag

The tag node.k8s.amazonaws.com/no_manage is read by the aws-node daemonset to determine whether an ENI attached to the machine should not be configured or used for private IPs.

This tag is not set by the cni plugin itself, but rather may be set by a user to indicate that an ENI is intended for host networking pods, or for some other process unrelated to Kubernetes.

Note: Attaching an ENI with the no_manage tag will result in an incorrect value for the Kubelet's --max-pods configuration option. Consider also updating the MAX_ENI and --max-pods configuration options on this plugin and the kubelet respectively if you are making use of this tag.

Container Runtime

For VPC CNI >=v1.12.0, IPAMD have switched to use an on-disk file /var/run/aws-node/ipam.json to track IP allocations, thus became container runtime agnostic and no longer requires access to Container Runtime Interface(CRI) socket.

• Note:
  • Helm chart >=v1.2.0 is released with VPC CNI v1.12.0, thus no longer supports the cri.hostPath.path. If you need to install a VPC CNI <v1.12.0 with helm chart, a Helm chart version that <v1.2.0 should be used.

For VPC CNI <v1.12.0, IPAMD still depends on CRI to track IP allocations using pod sandboxes information upon its starting.

• By default the dockershim CRI socket was mounted but can be customized to use other CRI:
  • The mountPath should be changed to /var/run/cri.sock and hostPath should be pointed to CRI used by kubelet, such as /var/run/containerd/containerd.sock for containerd.
  • With Helm chart <v1.2.0, the flag --set cri.hostPath.path=/var/run/containerd/containerd.sock can set above for you.
• Note:
  • When using a different container runtime instead of the default dockershim in VPC CNI, make sure kubelet is also configured to use the same CRI.
  • If you want to enable containerd runtime with the support provided by Amazon AMI, please follow the instructions in our documentation, Enable the containerd runtime bootstrap flag

Notes

L-IPAMD(aws-node daemonSet) running on every worker node requires access to the Kubernetes API server. If it can not reach the Kubernetes API server, ipamd will exit and CNI will not be able to get any IP address for Pods. Here is a way to confirm if aws-node has access to the Kubernetes API server.

# find out Kubernetes service IP, e.g. 10.0.0.1
kubectl get svc Kubernetes
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.0.0.1   <none>        443/TCP   29d

# ssh into worker node, check if worker node can reach API server
telnet 10.0.0.1 443
Trying 10.0.0.1...
Connected to 10.0.0.1.
Escape character is '^]'.  <-------- Kubernetes API server is reachable

Security disclosures

If you think you’ve found a potential security issue, please do not post it in the Issues. Instead, please follow the instructions here or email AWS security directly.

Contributing

See CONTRIBUTING.md