How To Get the Pod IP in Kubernetes

Kubernetes is an open-source platform for container orchestration. Its name originates from the Greek language and means "pilot" or "sailing master." In that sense, Kubernetes helps you navigate the tricky waters of cloud computing and containerized applications.

With Kubernetes, you can deploy, automate, and manage containerized applications, from service discovery and load balancing to automatic bin packing and configuration management. Kubernetes is widely used by many organizations to completely automate the orchestration of applications while reducing downtime.

When you dive into the Kubernetes architecture, you'll find Pods alongside other components. A Kubernetes Pod contains a collection of multiple, tightly coupled containers. By operating in the same environment, these containers share network and storage resources—including the IP address, network port, and network namespace. Nevertheless, containers can still run their own independent processes.

In this step-by-step tutorial, we’ll walk you through finding the IP address of a Kubernetes Pod, the service IP, and the Pod network namespaces.

Introduction to Kubernetes and Pod IPs

To understand Kubernetes, you must first be familiar with containers. Think of containers as specific environments that host an application alongside the code, dependencies, and libraries it requires to run. These containers allow applications to run smoothly on different platforms and operating systems.

However, when you have multiple containers, managing them can become challenging. This is where Kubernetes helps you with deployment and task automation.

At the core of Kubernetes, you'll find the networking module that controls how applications are deployed, how they communicate with the Kubernetes control plane, and how they communicate with each other.

Kubernetes has different communication methods between components, including communication between Pods on other nodes, Pods on the same node, and containers in the same Pod.

Pod-to-Pod communication lays the groundwork for the Kubernetes networking model, as it facilitates easy communication between Pods in accordance with network policies set by the network plug-in.

Each Pod is assigned a unique IP address upon initialization, which facilitates communication. Specifically, containers in a Pod share the same network namespace, IP address, and resources and can all reach each other's ports on localhost. This lets containers easily communicate with other containers in the same Pod while still being isolated.

Because Pods share the same network namespace, network address translation (NAT) is not needed for Pod-to-Pod communication. However, network policies are used to isolate Pods and restrict what each Pod can communicate with (like creating a firewall between Pods).

What is the kubelet?

In Kubernetes, the kubelet is responsible for applying, creating, updating, and destroying containers on a Kubernetes node. It registers the node with the API server using the hostname, a flag to override the hostname, or a particular logic for a cloud provider. The kubelet deals with Pod specifications defined in YAML or JSON format.

Extending Kubernetes with add-ons

Kubernetes is often used in conjunction with third-party networks to extend its functionality. This is done by leveraging the Kubernetes Container Network Interface (CNI) plug-in framework.

A few commonly used add-ons include Kubenet, Contrail, Flannel, Open VSwitch, and Project Calico. For example, the Flannel CNI plug-in works with Flannel on start-up to fetch the Pod CIDR and other network details from the API server and store them in a file.

Understanding Pods in Kubernetes

Kubernetes does not handle containers directly. Instead, these containers are placed in units known as Pods. Kubernetes pods are the smallest units to compute that can hold single or multiple containers. Containers in a Pod operate in the same environment, where they can share the same resources but still run isolated processes.

Among the shared resources are IP address, network port, and network namespace. Pods manage networks by allowing hosted containers to use their IP addresses to communicate with other containers. Similarly, Pods can also communicate with other Pods using their unique IP addresses.

The Kubernetes ecosystem extends further to include components like nodes, which are responsible for running Pods. These nodes can be grouped further into a Kubernetes cluster, which is managed using the control plane component. Within the nodes, there are different states (and Get Nodes is a command to gain the status of all nodes).

Prerequisites for retrieving Pod IPs

To retrieve Pod IPs, you must have access to a Kubernetes cluster that hosts your target Pods. The Kubernetes cluster can either be hosted locally or on cloud platforms. You also need the kubectl command line tool to control nodes and Pods. Plus, you must be familiar with different Kubernetes commands like kubectl config <context>.

How to get the Pod IP

Pods are ephemeral, meaning they can't be brought back once terminated. Each Pod is automatically assigned its own IP address, which is shared by the containers inside the Pod. By default, Pods don’t expose an external IP address because kube-proxy is responsible for managing all traffic on each node.

You might need to know the IP address of a Kubernetes Pod for several reasons, such as when deploying applications or working inside the cluster.

Using the kubectl command, you can easily find the IP address of a Kubernetes pod. We'll walk you through the steps below.

1. Accessing the Kubernetes cluster

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Use the command-line tool, also known as kubectl, to find the IP address of a Kubernetes Pod.

This tool fetches Pod information from the Kubernetes API to let you run Kubernetes commands to deploy applications, inspect and manage cluster resources, and view logs.

Use these links to install kubectl on Linux, macOS, or Windows.

• Install kubectl on Linux
• Install kubectl on macOS
• Install kubectl on Windows

2. Locating the specific Pod

Once you have installed the kubectl command-line tool, run the kubectl get pods command on Kubernetes node to find the Pod's name.

--CODE language-markup--
kubectl get pods

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3. Using kubectl to retrieve the Pod IP

Next, copy the pod's name and run the kubectl get pods server deployment command. This will revert a list of information, including the Pod's IP.

In the below case, the Pod's name is myapp-1234.

--CODE language-markup line-numbers--
kubectl get pod myapp-1234 -o
custom-columns=NAME:metadata.name,IP:status.podIP

Note: Assign each node a unique subnet to ensure all Pods across the cluster have a unique IP address (Pods are assigned IP addresses on that node).

How to find the service IP in Kubernetes

In Kubernetes, a service is a REST object, representing a deployed group of Pods in a cluster that all perform the same function. In simpler words, a service is a logical abstraction that connects Pods to a service name and a unique IP address. This is called clusterIP in Kubernetes.

Find the IP address of a Kubernetes service by using kubectl. Use the following command to list all services in all namespaces:

--CODE language-markup--
kubectl get service --all-namespaces

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Find the service IP in the CLUSTER-IP column.

Service IP addresses are different from Pod IP addresses as they are not answered by a single host. Instead, virtual IP addresses defined by kube-proxy are redirected and transported to an appropriate endpoint.

The environment variables and DNS for services are populated according to the virtual IP address of the service and the port.

How do Kubernetes services work?

Any request received by the service is redirected to the respective Pods. This makes the service a stable endpoint for communication between clients and Pods. Kubernetes's kube-proxy component uses iptables to direct service traffic to Pods randomly.

The default protocol for services is TCP; you can also use any supported protocol, including UDP and SCTP.

Kubernetes has five types of services:

• Cluster IP. This is the default service used to expose a service on a cluster-internal IP, which means the service is only accessible from inside the cluster.
• Node port. This exposes a service on each node's IP at a static port, making the service accessible from outside the cluster.
• Load balancer. This uses a cloud provider's load balancer to access a service from outside the cluster.
• External name. This maps a service to the contents of a predefined external name field by returning a CNAME record with its value.
• Headless. This headless service is used for Pod grouping when a stable IP address is not required.

Finding pod network namespaces

Network namespaces (or netns) isolate groups of resources within a single cluster. They are helpful for different teams and projects sharing a Kubernetes cluster.

The namespace provides a unique scope for named resources, delegates management authority to trusted users, and allows for community resource consumption limits. Although the names of resources within a namespace must be unique, resources across namespaces can differ.

Each Kubernetes Pod has its own Pod network namespace. Running commands from within a Pod's namespace is useful for effective deployment and operation, such as when checking the DNS resolution or the general network connectivity.

To run commands from within a Pod's netns, you first need to identify the process ID of one of the containers in a Pod. Below, we'll walk you through how to do this.

First, use the following command to list the containers running on a node:

First, use the following command to list the containers running on a node:‍

--CODE language-markup--
docker ps

Find the container ID or name of any container in the pod and use it in the following docker command:Find the container ID or name of any container in the Pod and use it in the following docker command:

--CODE language-markup--
‍docker inspect --format '{{ .State.Pid }}' container-id-or-name

You should now see a process ID (or PID) in the output, which can be used to run the nsenter program to run a command in that process's network namespace. By using nsenter instead of docker exec to run commands, you receive access to all the commands available on the node, not just those installed in containers.

--CODE language-markup--
nsenter -t your-container-pid -n ip addr

Note: Ensure you're using your own PID and change ip addr according to the command you'd like to run inside the Pod's network namespace.

Common challenges and troubleshooting

Different issues can occur when working with Kubernetes Pods and IP addresses. One of the most common challenges in encountering the CrashLoopBackOff error.

In some cases, you may fail to find your Pod IP address simply because the target Pod isn't working. The CrashLoopBackOff error is usually caused by insufficient resources and can be easily identified using the kubectl get pods command. You can resolve the error by ejecting certain non-essential Pods from the cluster.

Best practices for managing Pod IPs

Pod IPs facilitate seamless communication not only between Pods but also between the hosted application containers. Here are some best practices for managing Pod IPs:

• Keep track of Pod IPs. Pod IPs can change when the host node is moved to a different cluster or due to network reconfiguration. In such cases, you'll need to track Pod IPs, ensuring other Pods and containers are always connecting to the right IP address.
• Automate IP management. Use automation tools to help manage traffic and security policies, especially when running ever-changing containers.
• Consider security. Apply network policies to control traffic flow at the IP address level to enhance security.

Use your Kubernetes skills on Upwork

Kubernetes ensures high availability of applications, resource efficiency, and scalability. Pods, which are core Kubernetes components, host containers with your application logic. Understanding how Pods work, including their IP addresses, can help you facilitate seamless communication between multiple containers or between different Pods.

Looking to master Kubernetes fundamentals? Start by reading through the official reference docs on kubernetes.io. Next, enroll in online learning platforms like Udemy and Udacity to deepen your understanding of Kubernetes.

As you continue learning the necessary skills, consider working with experienced Kubernetes experts on Upwork to help you with Kubernetes setup and management.

Once you have the desired skills and qualifications, join Upwork to connect with businesses that need your expertise by browsing available Kubernetes jobs.

Upwork is not affiliated with and does not sponsor or endorse any of the tools or services discussed in this section. These tools and services are provided only as potential options, and each reader and company should take the time needed to adequately analyze and determine the tools or services that would best fit their specific needs and situation.