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Reachability to Kubernetes Pods Using the IP Fabric Forwarding Feature
This topic covers Contrail Networking in Kubernetes-orchestrated environments that are using Contrail Networking Release 21-based releases.
Starting in Release 22.1, Contrail Networking evolved into Cloud-Native Contrail Networking. Cloud-Native Contrail Networking offers significant enhancements to optimize networking performance in Kubernetes-orchestrated environments. We recommend using Cloud-Native Contrail for networking in most Kubernetes-orchestrated environments.
For general information about Cloud-Native Contrail, see the Cloud-Native Contrail Networking Techlibrary homepage.
This topic describes updates to Kubernetes and supported features in Contrail.
TLS Bootstrapping of Kubernetes Nodes
Contrail supports TLS Bootstrapping of Kubernetes Nodes starting in Contrail Networking Release 5.1. TLS bootstrapping streamlines Kubernetes’ ability to add and remove nodes from the Contrail cluster.
Priority Based Multitenancy
Contrail supports priority on the various resource quotas through the ResourceQuotaScopeSelector feature starting in Contrail Networking Release 5.1.
Contrail Networking supports improved pod autoscaling by creating and deleting pods based on the load starting in Contrail Networking Release 5.1.
Reachability to Kubernetes Pods Using the IP Fabric Forwarding Feature
A Kubernetes pod is a group of one or more containers (such as Docker containers), the shared storage for those containers, and options on how to run the containers. Since pods are in the overlay network, they cannot be reached directly from the underlay without a gateway or vRouter. Starting in Contrail Networking Release 5.0, the IP fabric forwarding (ip-fabric-forwarding) feature enables virtual networks to be created as part of the underlay network and eliminates the need for encapsulation and decapsulation of data. The ip-fabric-forwarding feature is only applicable for pod networks. If ip-fabric-forwarding is enabled, pod-networks are associated to ip-fabric-ipam instead of pod-ipam which is also a flat subnet.
The ip-fabric-forwarding feature is enabled and disabled in
the global and namespace levels. By default, ip-fabric-forwarding is disabled in the global level. To enable it in global level, you
must set “ip_fabric_forwarding” to “true” in the “[KUBERNETES]” section of the
/etc/contrail/contrail-kubernetes.conf file. To
enable or disable the feature in namespace level, you must set “ip_fabric_forwarding” to “true” or “false” respectively in namespace annotation.
For example, “opencontrail.org/ip_fabric_forwarding”:
“true”. Once the feature is enabled, it cannot be
For more information, see Gateway-less Forwarding.
Service Isolation Through Virtual Networks
In namespace isolation mode, services in one namespace are not accessible from other namespaces, unless security groups or network policies are explicitly defined to allow access. If any Kubernetes service is implemented by pods in an isolated namespace, those services are reachable only to pods in the same namespace through the Kubernetes service-ip.
The Kubernetes service-ip is allocated from the cluster network despite being in an isolated namespace. So, by default, service from one namespace can reach services from another namespace. However, security groups in isolated namespaces prevent reachability from external namespace and also prevent reachability from outside of the cluster. In order to enable access by external namespaces, the security group must be edited to allow access to all namespaces which defeats the purpose of isolation.
Contrail Networking—starting in Contrail Networking Release 5.0—enables service or ingress reachability from external clusters in isolated namespaces. Two virtual networks are created in isolated namespaces. One network is dedicated to pods and one is dedicated to services. Contrail network-policy is created between the pod network and the service network for reachability between pods and services. Service uses the same service-ipam which is a flat-subnet like pod-ipam. It is applicable for default namespace as well.
Contrail ip-fabric-snat Feature
With the Contrail ip-fabric-snat feature, pods that are in the overlay can reach the Internet without floating IPs or a logical-router. The ip-fabric-snat feature uses compute node IP for creating a source NAT to reach the required services and is applicable only to pod networks. The kube-manager reserves ports 56000 through 57023 for TCP and 57024 through 58047 for UDP to create a source NAT in global-config during the initialization.
The ip-fabric-snat feature can be enabled or disabled in the
global or namespace levels. By default, the feature is disabled in
the global level. To enable the ip-fabric-snat feature in the global
level, you must set “ip-fabric-snat” to “true” in the “[KUBERNETES]” section in the
/etc/contrail/contrail-kubernetes.conf file. To enable or disable it in the namespace level, you must set “ip_fabric_snat” to “true” or “false” respectively in namespace annotation.
For example, “opencontrail.org/ip_fabric_snat”: “true”. The ip_fabric_snat feature can be at enabled and disabled any time.
To enable or disable the ip_fabric_snat feature in the default-pod-network,
default namespace must be used. If the ip_fabric_forwarding is enabled, ip_fabric_snat is ignored.
For more information, see Distributed SNAT.
Third-Party Ingress Controllers
Multiple ingress controllers can co-exist in Contrail. If “kubernetes.io/ingress.class” is absent or is “opencontrail” in the annotations of the Kubernetes ingress resource, the kube-manager creates a HAProxy loadbalancer. Otherwise it is ignored and the respective ingress controller handles the ingress resource. Since Contrail ensures the reachability between pods and services, any ingress controller can reach the endpoints or pods directly or through services.
Custom Network Support for Ingress Resources
Contrail supports custom networks in namespace level for pods. Starting with Contrail Release 5.0, custom networks are supported for ingress resources as well.
Kubernetes Probes and Kubernetes Service Node-Port
The Kubelet needs reachability to pods for liveness and readiness probes. Contrail network policy is created between the IP fabric network and pod network to provide reachability between node and pods. Whenever the pod network is created, the network policy is attached to the pod network to provide reachability between node and pods. So, any process in the node can reach the pods.
Kubernetes Service Node-Port is based on node reachability to pods. Since Contrail provides connectivity between node and pods through Contrail the network policy, Node Port is supported.
Kubernetes Network-Policy Support
Contrail Networking supports the following Kubernetes release 1.12 network policy features:
Egress support for network policy—Each NetworkPolicy includes a policyTypes list which can include either Ingress, Egress, or both. The policyTypes field indicates whether or not the given policy applies to ingress traffic to selected pod, egress traffic from the selected pod, or both. Contrail Networking—starting in Contrail Networking Release 5.1—supports the podSelector&namespaceSelector egress specification. Contrail Networking—starting in Contrail Networking Release 5.0—supports podSelector, namespaceSelector, and egress CIDR egress specifications.
Classless Interdomain Routing (CIDR) selector support for egress and ingress network policies
Contrail-ansible-deployer provisioning—Contrail-ansible-deployer is updated to support Kubernetes 1.12.
Contrail Networking supports Kubernetes release 1.9.2 and enables implementing Kubernetes network policy in Contrail using the Contrail firewall security policy framework. While Kubernetes network policy can be implemented using other security objects in Contrail like security groups and Contrail network policies, the support of tags by Contrail firewall security policy aids in the simplification and abstraction of workloads.
For more information, see Implementation of Kubernetes Network Policy with Contrail Firewall Policy.