Does K8s run on a plain Layer2 network with no support for Layer3 routing stuff?!?
Im asking as I want to switch my K8s envirnoment from cloud VMs over to Bare Metal and Im not aware of the Privat-network Infrastrcture of the hoster ...
Kind regards and thanks in advance
Kubernetes will run on a more classic, statically defined network you would find on a private network (but does rely on layer 4 networking).
A clusters IP addressing and routing can be largely configured for you by one of the CNI plugins that creates an overlay network or can be configured statically with a bit more work (via kubenet/IPAM).
An overlay network can be setup with tools like Calico, Flannel or Weave that will manage all the routing in cluster as long as all the k8s nodes can route to each other, even over disparate networks. Kubespray is a good place to start with deploying clusters like this.
For a static network configuration, clusters will need permanent static routes added for all the networks kubernetes uses. The "magic" cloud providers and the overlay CNI plugins provide is to is to be able to route all those networks automatically. Each node will be assigned a Pod subnet and every node in the cluster will need to have a route to those IP's
Related
Maybe I am way off in my pursuit to create as close to real a Kubernetes setup on a local network :-)
Is it possible to use Parallels(Desktop) RAS as a Loadbalancer for Kubernetes?
1. I am running a master node in Ubuntu on Parallels Desktop
2. And some worker nodes also in Parallels Desktop
Both using a bridge network.
It would be cool if it is possible to have a setup including a LoadBalancer.
You could use MetalLB, KubeVIP, or Keepalived-operator (with HAProxy). I played around with KubeVIP but now use MetalLB L2 in my RasberryPi based Kubernetes cluster. MetalLB BGP would be even better if you have a router that supports the protocol (such as Unifi). The following references might help further:
https://www.openshift.com/blog/self-hosted-load-balancer-for-openshift-an-operator-based-approach
https://www.youtube.com/watch?v=9PLw1xalcYA
http://blog.cowger.us/2019/02/10/using-metallb-with-the-unifi-usg-for-in-home-kubernetes-loadbalancer-services.html
I have a Kubernetes cluster setup with on bare-metal local nodes(all nodes are accessible through the public network and private network ).
I want to add an EC2 node to this cluster.
I have four nodes as MASTER, WORKER-1, WORKER-2, EC2-NODE.
MASTER, WORKER-1, WORKER-2 has full connectivity through the public and private networks.
But EC2-NODE is only accessible on public networks from any node.
I have tried joining the EC2 node to the cluster and give --node-ip=$public_ip_of_ec2_node,
EC2 node joined successfully and mark as ready but services are not reachable from other nodes to the EC2 node. It joins on the private network interface (eth0) and exposes the private IP of the EC2 node to the cluster.
In the Kubernetes, there is a requirement that all nodes have full internet connectivity between them either private or public. What does it mean?
Is it required to have a single network interface among nodes?
Any help would be nice.
Thank you in advance.
System Info:
Kuberenetes version: 1.16.2
Pod network: Flannel
Let's start with understanding how to implement the Kubernetes networking model:
There are a number of ways that this network model can be implemented.
This document is not an exhaustive study of the various methods, but
hopefully serves as an introduction to various technologies and serves
as a jumping-off point.
There you can find a list of networking options. Among them there is Flannel:
Flannel is a very simple overlay network that satisfies the Kubernetes
requirements. Many people have reported success with Flannel and
Kubernetes.
Flannel is responsible for providing a layer 3 IPv4 network between
multiple nodes in a cluster. Flannel does not control how containers
are networked to the host, only how the traffic is transported between
hosts. However, flannel does provide a CNI plugin for Kubernetes and a
guidance on integrating with Docker.
You are already using Flannel as a CNI plugin.
Please let me know if you find the info above helpful.
In GCloud we have one Kubernetes cluster with two nodes, it is possible to setup all nodes to get the same external IP? Now we are getting two external IP's.
Thank you in advance.
The short answer is no, you cannot assign the very same external IP to two nodes or two instances, but you can use the same IP to access them, for example through a LoadBalancer.
The long answer
Depending on your scenario and the infrastructure you want to set up, several ways are available to expose different resources through the very same IP.
I do not know why you want to assign the same IP to the nodes, but since each node it is a Google Compute Engine instance you can set up a Load Balancer (TCP, SSL, HTTP(s), internal, ecc). In this way you reach the nodes as if they were not part of a Kubernetes cluster, basically you are treating them as Compute Engine instances and you will able to connect to any port they are listening on (for example an HTTP server or an external health check).
Notice that you will be not able to connect to the PODs in this way: the services and the containers are running in a separate software bases network and they will be not reachable if not properly set, for example with a NodePort.
On the other hand if you are interested in making your PODs running in two different kubernetes nodes reachable through a unique entry point you have to set up Kubernetes related ingress and load balancing to expose your services. This resources are based as well on the Google Cloud Platform Load Balancer components, but when created they trigger as well the required change to the Kubernetes Network.
I am new to Dockers and containers. I was going through the tutorials for docker and came across this information.
https://docs.docker.com/get-started/part3/#docker-composeyml
networks:
- webnet
networks:
webnet:
What is webnet? The document says
Instruct web’s containers to share port 80 via a load-balanced network called webnet. (Internally, the containers themselves will publish to web’s port 80 at an ephemeral port.)
So, by default, the overlay network is load balanced in docker cluster? What is load balancing algo used?
Actually, it is not clear to me why do we have load balancing on the overlay network.
Not sure I can be clearer than the docs, but maybe rephrasing will help.
First, the doc you're following here uses what is called the swarm mode of docker.
What is swarm mode?
A swarm is a cluster of Docker engines, or nodes, where you deploy services. The Docker Engine CLI and API include commands to manage swarm nodes (e.g., add or remove nodes), and deploy and orchestrate services across the swarm.
From SO Documentation:
A swarm is a number of Docker Engines (or nodes) that deploy services collectively. Swarm is used to distribute processing across many physical, virtual or cloud machines.
So, with swarm mode you have a multi host (vms and/or physical) cluster a machines that communicate with each other through their docker engine.
Q1. What is webnet?
webnet is the name of an overlay network that is created when your stack is launched.
Overlay networks manage communications among the Docker daemons participating in the swarm
In your cluster of machines, a virtual network is the created, where each service has an ip - mapped to an internal DNS entry (which is service name), and allowing docker to route incoming packets to the right container, everywhere in the swarm (cluster).
Q2. So, by default, overlay network is load balanced in docker cluster ?
Yes, if you use the overlay network, but you could also remove the service networks configuration to bypass that. Then you would have to publish the port of the service you want to expose.
Q3. What is load balancing algo used ?
From this SO question answered by swarm master bmitch ;):
The algorithm is currently round-robin and I've seen no indication that it's pluginable yet. A higher level load balancer would allow swarm nodes to be taken down for maintenance, but any sticky sessions or other routing features will be undone by the round-robin algorithm in swarm mode.
Q4. Actually it is not clear to me why do we have load balancing on overlay network
Purpose of docker swarm mode / services is to allow orchestration of replicated services, meaning that we can scale up / down containers deployed in the swarm.
From the docs again:
Swarm mode has an internal DNS component that automatically assigns each service in the swarm a DNS entry. The swarm manager uses internal load balancing to distribute requests among services within the cluster based upon the DNS name of the service.
So you can have deployed like 10 exact same container (let's say nginx with you app html/js), without dealing with private network DNS entries, port configuration, etc... Any incoming request will be automatically load balanced to hosts participating in the swarm.
Hope this helps!
Having set up a kubernetes cluster with calico for the one-ip-per-pod networking, I'm wondering what the best practise is to expose services to the outside world.
IMHO I got two options here, BGP'ing the internal pod IP's (172...) to an edge router/firewall (vyos in my case) and do an SNAT on the firewall / router. But then I'd need one public IP per pod to expose.
Pro: less public IP's need to be used
Con: Pod changes need updated firwall rules?!
Or 2nd: Taking the provided public network and hand it over to calico as an IP pool to be used for the pods.
Con: lots of public IP's wasted for internal services which won't get exposed to the internet
Hope someone could enlighten me or point me in the right direction.
Thanks!
Calico doesn't provide any special way to expose services in Kubernetes. You should use standard Kubernetes services, node ports and the like to expose your services. In the future, there's a possibility that Calico will offer some of the features that kube-proxy currently does for Kubernetes (such as exposing service IPs) but right now, Calico fits in at the low-level networking API layer only. Calico's real strength in the Kubernetes integration is the ability to define network security policy using the new Kubernetes NetworkPolicy API.
Source: I'm one of Calico's core developers.
Calico is not responsible for the k8s service IP management or for translating service ip to container (workload endpoint) It allocates IP addressses to the newly created pods and does necessary system config changes to implement the calico policies