通过负载均衡器 ip 从 kubernetes pod 发送请求

Question

I have a k8s cluster on DigitalOcean using traefik 1.7 as Ingress Controller. our domain point to the load balancer ip created by trafik .

All incomming request go through load balancer ip and be routed by trafik to proper service.

Now I want to perform HTTP requests from my services to an external system which only accepts registered IPs.

Can I provide them load balancer's IP and make all outbound requests go through load balancer IP? or I need to provide them all node's public IPs?

thanks

Answer 1

You can do either of them.

But the best solution to this would be to make all the traffic go through load balancer assuming this is some proxy server with tunnelling capabilities and open comms through load balancer IP on your external system. Because, imagine, right now you might be having a dozen of nodes running 100 micro services and now you opened your external system security group to allow traffic from dozen.

But in next few months you might go from 12 to 100 nodes and the overhead of updating your external system's security group whenever you add a node in DigitalOcean.

But you can also try a different approach by adding a standalone proxy server and route traffic through it from your pods. Something like [this] ( Kubernetes outbound calls to an external endpoint with IP whitelisting ).

Just a note, it's not just these options there are several ways one can achieve this, one another approach would be associating a NAT IP to all your nodes and keeping every node behind a private network would also work. It all depends on how you want to set it up and the purpose of the system you are planning to achieve.

Hope this helps.

Answer 2

Unfortunately, Ingress resources can't use outbound requests. So you need to provide all nodes public IPs.

Another idea, if you use a forward proxy(eg nginx, haproxy), you can limit the nodes where forward proxy pods are scheduled by setting nodeSelector. By doing so, I think you can limit the nodes that provide public IP addresses.

Answer 3

Egress packets from a k8s cluster to cluster-external services have node's IP as the source IP. So, you can register k8s nodes' IPs in the external system to allow egress packets from the k8s cluster.

https://kubernetes.io/docs/tutorials/services/source-ip/ says egress packets from k8s get source NAT'ed with node's IP:

Source NAT : replacing the source IP on a packet, usually with a node's IP

Following can be used to send egress packets from a k8s cluster:

• k8s network policies
• calico CNI egress policies
• istio egress gateway
• nirmata/kube-static-egress-ip GitHub project

Answer 4

kube-static-egress-ip provides a solution with which a cluster operator can define an egress rule where a set of pods whose outbound traffic to a specified destination is always SNAT'ed with a configured static egress IP. kube-static-egress-ip provides this functionality in Kubernetes native way using custom rerources.