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Understanding loxilb deployment in K8s with kube-loxilb

What is kube-loxilb ?

kube-loxilb is loxilb's implementation of kubernetes service load-balancer spec which includes support for load-balancer class, advanced IPAM (shared or exclusive) etc. kube-loxilb runs as a deloyment set in kube-system namespace. It is a control-plane component that always runs inside k8s cluster and watches k8s system for changes to nodes/end-points/reachability/LB services etc. It acts as a K8s Operator of loxilb. The loxilb component takes care of doing actual job of providing service connectivity and load-balancing. So, from deployment perspective we need to run kube-loxilb inside K8s cluster but we have option to deploy loxilb in-cluster or external to the cluster.

The rationale of external mode is to provide users a similar look and feel whether running loxilb in an on-prem or public cloud environment. Public-cloud environments usually run load-balancers/firewalls externally in order to provide a secure/dmz perimeter layer outside actual workloads.

At the same time, in-cluster mode is useful if an user needs everything in a self-contained Kubernetes cluser. When deploying in-cluster mode, all components of loxilb are managed by Kubernetes itself as Daemonset/Deployment.

loxilb users are free to choose any mode (in-cluster mode or external mode) as per convenience and their system architecture. The following blogs give detailed steps for :

  1. Running loxilb in external node with AWS EKS
  2. Running in-cluster LB with K3s for on-prem use-cases

This usually leads to another query - In external mode, who will be responsible for managing this entity ?

In public cloud(s), it is as simple as spawning a new instance in your VPC and launch loxilb docker in it. For on-prem cases, you need to run loxilb docker in a spare node/vm as applicable. loxilb docker is a self-contained entity and easily managed with well-known tools like docker, containerd, podman etc. It can be independently restarted/upgraded anytime and kube-loxilb will make sure all the k8s LB services are properly configured each time.

Overall topology

  • For external mode, the overall topology including all components should be similar to the following :

loxilb topology

  • For in-cluster mode, the overall topology including all components should be similar to the following :

loxilb topology

How to deploy kube-loxilb ?

  • If you have chosen external-mode, please make sure loxilb docker is downloaded and installed properly in a node external to your cluster. One can follow guides here or refer to various other documentation . It is important to have network connectivity from this node to the k8s cluster nodes (where kube-loxilb will eventually run) as seen in the above figure. (PS - This step can be skipped if running in-cluster mode)

  • Download the kube-loxilb config yaml :

wget https://github.com/loxilb-io/kube-loxilb/raw/main/manifest/ext-cluster/kube-loxilb.yaml
  • Modify arguments as per user's needs :
        args:
            - --loxiURL=http://12.12.12.1:11111
            - --cidrPools=defaultPool=123.123.123.1/24
            #- --cidrPools=defaultPool=123.123.123.1/24,pool2=124.124.124.1/24
            #- --cidrPools=defaultPool=3ffe::1/96
            #- --monitor
            #- --setBGP=65100
            #- --extBGPPeers=50.50.50.1:65101,51.51.51.1:65102
            #- --enableBGPCRDs
            #- --setRoles=0.0.0.0
            #- --setLBMode=1
            #- --setUniqueIP=false

The arguments have the following meaning :

Name Description
loxiURL API server address of loxilb. This is the docker IP address loxilb docker of Step 1. If unspecified, kube-loxilb assumes loxilb is running in-cluster mode and autoconfigures this.
cidrPools CIDR or IPAddress range to allocate addresses from. By default address allocated are shared for different services(shared Mode). Multiple pools can be defined and any of them can be selected during service creation using "loxilb.io/poolSelect" annotation. cidrPools can be specified as ip-cidr e.g 123.123.123.0/24 or as ip-ranges e.g 192.168.20.100-192.168.20.105
cidr6Pools Ipv6 CIDR or IPAddress range to allocate addresses from. By default address allocated are shared for different services(shared Mode)
monitor Enable liveness probe for the LB end-points (default : unset)
setBGP Use specified BGP AS-ID to advertise this service. If not specified BGP will be disabled. Please check here how it works.
extBGPPeers Specifies external BGP peers with appropriate remote AS
setRoles If present, kube-loxilb arbitrates loxilb role(s) in cluster-mode. Further, it sets a special VIP (selected as sourceIP) to communicate with end-points in full-nat mode.
setLBMode 0, 1, 2
0 - default (only DNAT, preserves source-IP)
1 - onearm (source IP is changed to load balancer’s interface IP)
2 - fullNAT (sourceIP is changed to virtual IP)
setUniqueIP Allocate unique service-IP per LB service (default : false)
enableBGPCRDs Enable BGP Policy and Peer CRDs

Many of the above flags and arguments can be overriden on a per-service basis based on loxilb specific annotation as mentioned below.

  • kube-loxilb supported annotations:
Annotations Description
loxilb.io/multus-nets When using multus, the multus network can also be used as a service endpoint.Register the multus network name to be used.

Example:
apiVersion: v1
kind: Service
metadata:
  name: multus-service
  annotations:
    loxilb.io/multus-nets: macvlan1,macvlan2
spec:
  externalTrafficPolicy: Local
  loadBalancerClass: loxilb.io/loxilb
  selector:
    app: pod-01
  ports:
  - port: 55002
    targetPort: 5002
  type: LoadBalancer
loxilb.io/poolSelect You can specify the IP Pool name from which external IP address will be allocated and assigned to the service. If this annotation is not present, it defaults to "defaultPool"

Example:
metadata:
  name: sctp-lb1
  annotations:
    loxilb.io/poolSelect: “pool1”
spec:
  loadBalancerClass: loxilb.io/loxilb
  selector:
    what: sctp-test
  ports:
   - port: 55002
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/poolSelectSecondary When using the SCTP multi-homing function, you can specify the number of secondary IP Pools(upto 3) from which secondary IP address can be assigned to the service. When used with the loxilb.io/secondaryIPs annotation, the value set in loxilb.io/poolSelectSecondary is ignored. (loxilb.io/secondaryIPs annotation takes precedence)

Example:
metadata:
  name: sctp-lb1
  annotations:
    loxilb.io/poolSelectSecondary: “pool2,pool3”
spec:
  loadBalancerClass: loxilb.io/loxilb
  selector:
    what: sctp-test
  ports:
   - port: 55002
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/secondaryIPs When using the SCTP multi-homing function, specify the secondary IP to be assigned to the service. Multiple IPs(upto 3) can be specified at the same time using a comma(,). When used with the loxilb.io/poolSelectSecondary annotation, loxilb.io/secondaryIPs takes priority.)

Example:
metadata:
name: sctp-lb-secips
  annotations:
    loxilb.io/lbmode: "fullnat"
loxilb.io/secondaryIPs: "1.1.1.1,2.2.2.2"
spec:
  loadBalancerClass: loxilb.io/loxilb
  selector:
    what: sctp-lb-secips
  ports:
   - port: 56004
     targetPort: 9999
     protocol: SCTP
  type: LoadBalancer
loxilb.io/staticIP Specifies the External IP to assign to the LoadBalancer service. By default, an external IP is assigned within the externalCIDR range set in kube-loxilb, but using the annotation, IPs outside the range can also be statically specified.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb-fullnat
  annotations:
    loxilb.io/lbmode: "fullnat"
    loxilb.io/staticIP: "192.168.255.254"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-fullnat-test
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/liveness Set LoxiLB to perform a health check (probe) based endpoint selection(If flag is set, only active endpoints will be selected). The default value is no, and when the value is set to yes, the probe function of the corresponding service is activated.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb-fullnat
  annotations:
    loxilb.io/liveness : "yes"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-fullnat-test
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/lbmode Set LB mode individually for each service. The values ​​that can be specified: "default", "onearm", "fullnat", "hostonearm", "fullproxy" and "dsr". Please refer to this document for more details.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb-fullnat
  annotations:
    loxilb.io/lbmode: "fullnat"
    spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-fullnat-test
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/ipam Specify which IPAM mode the service will use. Select one of three options: “ipv4”, “ipv6”, or “ipv6to4”.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/ipam : "ipv4"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/timeout Set the session retention time for the service.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/timeout : "60"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/probetype Specifies the protocol type to use for endpoint probe operations. You can select one of “udp”, “tcp”, “https”, “http”, “sctp”, “ping”, or “none”. Probetype is set to protocol type, if you are using lbMode as "fullnat" or "onearm". To set it off, use probetype : "none"

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/probetype : "ping"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/probeport Set the port to use for probe operation. It is not applied if the loxilb.io/probetype annotation is not used or if it is of type icmp or none.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/probetype : "tcp"
    loxilb.io/probeport : "3000"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/probereq Specifies API for the probe request. It is not applied if the loxilb.io/probetype annotation is not used or if it is of type icmp or none.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/probetype : "tcp"
    loxilb.io/probeport : "3000"
    loxilb.io/probereq : "health"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/proberesp Specifies the response to the probe request. It is not applied if the loxilb.io/probetype annotation is not used or if it is of type icmp or none.

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/probetype : "tcp"
    loxilb.io/probeport : "3000"
    loxilb.io/probereq : "health"
    loxilb.io/proberesp : "ok"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/probetimeout Specifies the timeout for starting a probe request (in seconds). The default value is 60 seconds

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/liveness : "yes"
    loxilb.io/probetimeout : "10"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/proberetries Specifies the number of probe request retries before considering an endpoint as inoperative. The default value is 2

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/liveness : "yes"
    loxilb.io/probetimeout : "10"
    loxilb.io/proberetries : "3"
spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/epselect Specifies the algorithm for end-point slection e.g "rr"/"roundrobin", "hash", "persist", "lc", "n2" and "n3" etc. The default value is "roundrobin".

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/liveness : "yes"
    loxilb.io/probetimeout : "10"
    loxilb.io/proberetries : "3"
    loxilb.io/epselect : "hash"
    spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
loxilb.io/usepodnetwork Whether to select PodIP and targetPort as EndPoints

Example:
apiVersion: v1
kind: Service
metadata:
  name: sctp-lb
  annotations:
    loxilb.io/liveness : "yes"
    loxilb.io/probetimeout : "10"
    loxilb.io/proberetries : "3"
    loxilb.io/usepodnetwork : "yes"
    spec:
  loadBalancerClass: loxilb.io/loxilb
  externalTrafficPolicy: Local
  selector:
    what: sctp-lb
  ports:
   - port: 56004
     protocol: SCTP
     targetPort: 9999
  type: LoadBalancer
  • Apply the yaml after making necessary changes :

kubectl apply -f kube-loxilb.yaml
* The above should make sure kube-loxilb is successfully running. Check kube-loxilb is running : 

k8s@master:~$ sudo kubectl get pods -A
NAMESPACE         NAME                                        READY   STATUS    RESTARTS   AGE
kube-system       local-path-provisioner-84db5d44d9-pczhz     1/1     Running   0          16h
kube-system       coredns-6799fbcd5-44qpx                     1/1     Running   0          16h
kube-system       metrics-server-67c658944b-t4x5d             1/1     Running   0          16h
kube-system       kube-loxilb-5fb5566999-ll4gs                1/1     Running   0          14h
  • Finally to create service LB for a workload, we can use and apply the following template yaml

(Note - Check loadBalancerClass and other loxilb specific annotation) :

        apiVersion: v1
        kind: Service
        metadata:
          name: iperf-service
          annotations:
           # If there is a need to do liveness check from loxilb
           loxilb.io/liveness: "yes"
           # Specify LB mode - one of default, onearm or fullnat 
           loxilb.io/lbmode: "default"
           # Specify loxilb IPAM mode - one of ipv4, ipv6 or ipv6to4 
           loxilb.io/ipam: "ipv4"
           # Specify number of secondary networks for multi-homing
           # Only valid for SCTP currently
           # loxilb.io/num-secondary-networks: "2
           # Specify a static externalIP for this service
           # loxilb.io/staticIP: "123.123.123.2"
        spec:
          loadBalancerClass: loxilb.io/loxilb
          selector:
            what: perf-test
          ports:
            - port: 55001
              targetPort: 5001
          type: LoadBalancer
        ---
        apiVersion: v1
        kind: Pod
        metadata:
          name: iperf1
          labels:
            what: perf-test
        spec:
          containers:
            - name: iperf
              image: eyes852/ubuntu-iperf-test:0.5
              command:
                - iperf
                - "-s"
              ports:
                - containerPort: 5001

Users can change the above as per their needs.

  • Verify LB service is created 
k8s@master:~$ sudo kubectl get svc
NAME                TYPE           CLUSTER-IP    EXTERNAL-IP         PORT(S)             AGE
kubernetes          ClusterIP      10.43.0.1     <none>              443/TCP             13h
iperf1              LoadBalancer   10.43.8.156   llb-192.168.80.20   55001:5001/TCP      8m20s
  • For more example yaml templates, kindly refer to kube-loxilb's manifest directory

Additional steps to deploy loxilb (in-cluster) mode

To run loxilb in-cluster mode, the URL argument in kube-loxilb.yaml needs to be commented out: 

        args:
            #- --loxiURL=http://12.12.12.1:11111
            - --externalCIDR=123.123.123.1/24

This enables a self-discovery mode of kube-loxilb where it can find and reach loxilb pods running inside the cluster. Last but not the least we need to create the loxilb pods in cluster : 

sudo kubectl apply -f https://github.com/loxilb-io/kube-loxilb/raw/main/manifest/in-cluster/loxilb.yaml

Once all the pods are created, the same can be verified as follows (you can see both kube-loxilb and loxilb components running: 

k8s@master:~$ sudo kubectl get pods -A
NAMESPACE         NAME                                        READY   STATUS    RESTARTS   AGE
kube-system       local-path-provisioner-84db5d44d9-pczhz     1/1     Running   0          16h
kube-system       coredns-6799fbcd5-44qpx                     1/1     Running   0          16h
kube-system       metrics-server-67c658944b-t4x5d             1/1     Running   0          16h
kube-system       kube-loxilb-5fb5566999-ll4gs                1/1     Running   0          14h
kube-system       loxilb-lb-mklj2                             1/1     Running   0          13h
kube-system       loxilb-lb-stp5k                             1/1     Running   0          13h
kube-system       loxilb-lb-j8fc6                             1/1     Running   0          13h
kube-system       loxilb-lb-5m85p                             1/1     Running   0          13h
Thereafter, the process of service creation remains the same as explained in previous sections.

How to use kube-loxilb CRDs ?

Kube-loxilb provides various Custom Resource Definition (CRD) to facilicate its run-time operations:

  1. Generic config CRDs. More info here
  2. BGP config CRDs. More info here