OVN-Kubernetes architecture

Introduction to OVN-Kubernetes architecture
Listing all resources in the OVN-Kubernetes project
Listing the OVN-Kubernetes northbound database contents
Command line arguments for ovn-nbctl to examine northbound database contents
Listing the OVN-Kubernetes southbound database contents
Command line arguments for ovn-sbctl to examine southbound database contents
OVN-Kubernetes logical architecture
- Installing network-tools on local host
- Running network-tools
Additional resources

Introduction to OVN-Kubernetes architecture

The following diagram shows the OVN-Kubernetes architecture.

Figure 1. OVK-Kubernetes architecture

The key components are:

Cloud Management System (CMS) - A platform specific client for OVN that provides a CMS specific plugin for OVN integration. The plugin translates the cloud management system’s concept of the logical network configuration, stored in the CMS configuration database in a CMS-specific format, into an intermediate representation understood by OVN.
OVN Northbound database (nbdb) - Stores the logical network configuration passed by the CMS plugin.
OVN Southbound database (sbdb) - Stores the physical and logical network configuration state for OpenVswitch (OVS) system on each node, including tables that bind them.
ovn-northd - This is the intermediary client between nbdb and sbdb. It translates the logical network configuration in terms of conventional network concepts, taken from the nbdb, into logical data path flows in the sbdb below it. The container name is northd and it runs in the ovnkube-master pods.
ovn-controller - This is the OVN agent that interacts with OVS and hypervisors, for any information or update that is needed for sbdb. The ovn-controller reads logical flows from the sbdb, translates them into OpenFlow flows and sends them to the node’s OVS daemon. The container name is ovn-controller and it runs in the ovnkube-node pods.

The OVN northbound database has the logical network configuration passed down to it by the cloud management system (CMS). The OVN northbound Database contains the current desired state of the network, presented as a collection of logical ports, logical switches, logical routers, and more. The ovn-northd (northd container) connects to the OVN northbound database and the OVN southbound database. It translates the logical network configuration in terms of conventional network concepts, taken from the OVN northbound Database, into logical data path flows in the OVN southbound database.

The OVN southbound database has physical and logical representations of the network and binding tables that link them together. Every node in the cluster is represented in the southbound database, and you can see the ports that are connected to it. It also contains all the logic flows, the logic flows are shared with the ovn-controller process that runs on each node and the ovn-controller turns those into OpenFlow rules to program Open vSwitch.

The Kubernetes control plane nodes each contain an ovnkube-master pod which hosts containers for the OVN northbound and southbound databases. All OVN northbound databases form a Raft cluster and all southbound databases form a separate Raft cluster. At any given time a single ovnkube-master is the leader and the other ovnkube-master pods are followers.

Listing all resources in the OVN-Kubernetes project

Finding the resources and containers that run in the OVN-Kubernetes project is important to help you understand the OVN-Kubernetes networking implementation.

Prerequisites

Access to the cluster as a user with the cluster-admin role.
The OpenShift CLI (oc) installed.

Procedure

Run the following command to get all resources, endpoints, and ConfigMaps in the OVN-Kubernetes project:

$ oc get all,ep,cm -n openshift-ovn-kubernetes

Example output

NAME                       READY   STATUS    RESTARTS      AGE
pod/ovnkube-master-9g7zt   6/6     Running   1 (48m ago)   57m
pod/ovnkube-master-lqs4v   6/6     Running   0             57m
pod/ovnkube-master-vxhtq   6/6     Running   0             57m
pod/ovnkube-node-9k9kc     5/5     Running   0             57m
pod/ovnkube-node-jg52r     5/5     Running   0             51m
pod/ovnkube-node-k8wf7     5/5     Running   0             57m
pod/ovnkube-node-tlwk6     5/5     Running   0             47m
pod/ovnkube-node-xsvnk     5/5     Running   0             57m

NAME                            TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)             AGE
service/ovn-kubernetes-master   ClusterIP   None         <none>        9102/TCP            57m
service/ovn-kubernetes-node     ClusterIP   None         <none>        9103/TCP,9105/TCP   57m
service/ovnkube-db              ClusterIP   None         <none>        9641/TCP,9642/TCP   57m

NAME                            DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR                                                 AGE
daemonset.apps/ovnkube-master   3         3         3       3            3           beta.kubernetes.io/os=linux,node-role.kubernetes.io/master=   57m
daemonset.apps/ovnkube-node     5         5         5       5            5           beta.kubernetes.io/os=linux                                   57m

NAME                              ENDPOINTS                                                        AGE
endpoints/ovn-kubernetes-master   10.0.132.11:9102,10.0.151.18:9102,10.0.192.45:9102               57m
endpoints/ovn-kubernetes-node     10.0.132.11:9105,10.0.143.72:9105,10.0.151.18:9105 + 7 more...   57m
endpoints/ovnkube-db              10.0.132.11:9642,10.0.151.18:9642,10.0.192.45:9642 + 3 more...   57m

NAME                                 DATA   AGE
configmap/control-plane-status       1      55m
configmap/kube-root-ca.crt           1      57m
configmap/openshift-service-ca.crt   1      57m
configmap/ovn-ca                     1      57m
configmap/ovnkube-config             1      57m
configmap/signer-ca                  1      57m

There are three ovnkube-masters that run on the control plane nodes, and two daemon sets used to deploy the ovnkube-master and ovnkube-node pods. There is one ovnkube-node pod for each node in the cluster. The ovnkube-config ConfigMap has the OKD OVN-Kubernetes configurations started by online-master and ovnkube-node.

List all the containers in the ovnkube-master pods by running the following command:
```
$ oc get pods ovnkube-master-9g7zt \
-o jsonpath='{.spec.containers[*].name}' -n openshift-ovn-kubernetes
```
Expected output
```
northd nbdb kube-rbac-proxy sbdb ovnkube-master ovn-dbchecker
```
The ovnkube-master pod is made up of several containers. It is responsible for hosting the northbound database (nbdb container), the southbound database (sbdb container), watching for cluster events for pods, egressIP, namespaces, services, endpoints, egress firewall, and network policy and writing them to the northbound database (ovnkube-master pod), as well as managing pod subnet allocation to nodes.
List all the containers in the ovnkube-node pods by running the following command:
```
$ oc get pods ovnkube-node-jg52r \
-o jsonpath='{.spec.containers[*].name}' -n openshift-ovn-kubernetes
```
Expected output
```
ovn-controller ovn-acl-logging kube-rbac-proxy kube-rbac-proxy-ovn-metrics ovnkube-node
```
The ovnkube-node pod has a container (ovn-controller) that resides on each OKD node. Each node’s ovn-controller connects the OVN northbound to the OVN southbound database to learn about the OVN configuration. The ovn-controller connects southbound to ovs-vswitchd as an OpenFlow controller, for control over network traffic, and to the local ovsdb-server to allow it to monitor and control Open vSwitch configuration.

List the currently elected OVN-Kubernetes master leader by running the following command:

$ oc get lease -n openshift-ovn-kubernetes

Expected output

NAME                    HOLDER                               AGE
ovn-kubernetes-master   ci-ln-gz990pb-72292-rthz2-master-2   50m

Listing the OVN-Kubernetes northbound database contents

To understand logic flow rules you need to examine the northbound database and understand what objects are there to see how they are translated into logic flow rules. The up to date information is present on the OVN Raft leader and this procedure describes how to find the Raft leader and subsequently query it to list the OVN northbound database contents.

Prerequisites

Access to the cluster as a user with the cluster-admin role.
The OpenShift CLI (oc) installed.

Procedure

Find the OVN Raft leader for the northbound database.

The Raft leader stores the most up to date information.

List the pods by running the following command:

$ oc get po -n openshift-ovn-kubernetes

Example output

NAME                   READY   STATUS    RESTARTS       AGE
ovnkube-master-7j97q   6/6     Running   2 (148m ago)   149m
ovnkube-master-gt4ms   6/6     Running   1 (140m ago)   147m
ovnkube-master-mk6p6   6/6     Running   0              148m
ovnkube-node-8qvtr     5/5     Running   0              149m
ovnkube-node-fqdc9     5/5     Running   0              149m
ovnkube-node-tlfwv     5/5     Running   0              149m
ovnkube-node-wlwkn     5/5     Running   0              142m

Choose one of the master pods at random and run the following command:

$ oc exec -n openshift-ovn-kubernetes ovnkube-master-7j97q \
-- /usr/bin/ovn-appctl -t /var/run/ovn/ovnnb_db.ctl \
--timeout=3 cluster/status OVN_Northbound

Example output

Defaulted container "northd" out of: northd, nbdb, kube-rbac-proxy, sbdb, ovnkube-master, ovn-dbchecker
1c57
Name: OVN_Northbound
Cluster ID: c48a (c48aa5c0-a704-4c77-a066-24fe99d9b338)
Server ID: 1c57 (1c57b6fc-2849-49b7-8679-fbf18bafe339)
Address: ssl:10.0.147.219:9643
Status: cluster member
Role: follower (1)
Term: 5
Leader: 2b4f (2)
Vote: unknown

Election timer: 10000
Log: [2, 3018]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->0000 ->0000 <-8844 <-2b4f
Disconnections: 0
Servers:
    1c57 (1c57 at ssl:10.0.147.219:9643) (self)
    8844 (8844 at ssl:10.0.163.212:9643) last msg 8928047 ms ago
    2b4f (2b4f at ssl:10.0.242.240:9643) last msg 620 ms ago (3)

1	This pod is identified as a follower
2	The leader is identified as `2b4f`
3	The `2b4f` is on IP address `10.0.242.240`

Find the ovnkube-master pod running on IP Address 10.0.242.240 using the following command:

$ oc get po -o wide -n openshift-ovn-kubernetes | grep 10.0.242.240 | grep -v ovnkube-node

Example output

ovnkube-master-gt4ms   6/6     Running             1 (143m ago)   150m   10.0.242.240   ip-10-0-242-240.ec2.internal   <none>           <none>

The ovnkube-master-gt4ms pod runs on IP Address 10.0.242.240.

Run the following command to show all the objects in the northbound database:
```
$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-gt4ms \
-c northd -- ovn-nbctl show
```
The output is too long to list here. The list includes the NAT rules, logical switches, load balancers and so on.

Run the following command to display the options available with the command ovn-nbctl:
```
$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-mk6p6 \
-c northd ovn-nbctl --help
```
You can narrow down and focus on specific components by using some of the following commands:

Run the following command to show the list of logical routers:

$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-gt4ms \
-c northd -- ovn-nbctl lr-list

Example output

f971f1f3-5112-402f-9d1e-48f1d091ff04 (GR_ip-10-0-145-205.ec2.internal)
69c992d8-a4cf-429e-81a3-5361209ffe44 (GR_ip-10-0-147-219.ec2.internal)
7d164271-af9e-4283-b84a-48f2a44851cd (GR_ip-10-0-163-212.ec2.internal)
111052e3-c395-408b-97b2-8dd0a20a29a5 (GR_ip-10-0-165-9.ec2.internal)
ed50ce33-df5d-48e8-8862-2df6a59169a0 (GR_ip-10-0-209-170.ec2.internal)
f44e2a96-8d1e-4a4d-abae-ed8728ac6851 (GR_ip-10-0-242-240.ec2.internal)
ef3d0057-e557-4b1a-b3c6-fcc3463790b0 (ovn_cluster_router)

From this output you can see there is router on each node plus an ovn_cluster_router.

Run the following command to show the list of logical switches:

$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-gt4ms \
-c northd -- ovn-nbctl ls-list

Example output

82808c5c-b3bc-414a-bb59-8fec4b07eb14 (ext_ip-10-0-145-205.ec2.internal)
3d22444f-0272-4c51-afc6-de9e03db3291 (ext_ip-10-0-147-219.ec2.internal)
bf73b9df-59ab-4c58-a456-ce8205b34ac5 (ext_ip-10-0-163-212.ec2.internal)
bee1e8d0-ec87-45eb-b98b-63f9ec213e5e (ext_ip-10-0-165-9.ec2.internal)
812f08f2-6476-4abf-9a78-635f8516f95e (ext_ip-10-0-209-170.ec2.internal)
f65e710b-32f9-482b-8eab-8d96a44799c1 (ext_ip-10-0-242-240.ec2.internal)
84dad700-afb8-4129-86f9-923a1ddeace9 (ip-10-0-145-205.ec2.internal)
1b7b448b-e36c-4ca3-9f38-4a2cf6814bfd (ip-10-0-147-219.ec2.internal)
d92d1f56-2606-4f23-8b6a-4396a78951de (ip-10-0-163-212.ec2.internal)
6864a6b2-de15-4de3-92d8-f95014b6f28f (ip-10-0-165-9.ec2.internal)
c26bf618-4d7e-4afd-804f-1a2cbc96ec6d (ip-10-0-209-170.ec2.internal)
ab9a4526-44ed-4f82-ae1c-e20da04947d9 (ip-10-0-242-240.ec2.internal)
a8588aba-21da-4276-ba0f-9d68e88911f0 (join)

From this output you can see there is an ext switch for each node plus switches with the node name itself and a join switch.

Run the following command to show the list of load balancers:

$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-gt4ms \
-c northd -- ovn-nbctl lb-list

Example output

UUID                                    LB                  PROTO      VIP                     IPs
f0fb50f9-4968-4b55-908c-616bae4db0a2    Service_default/    tcp        172.30.0.1:443          10.0.147.219:6443,10.0.163.212:6443,169.254.169.2:6443
0dc42012-4f5b-432e-ae01-2cc4bfe81b00    Service_default/    tcp        172.30.0.1:443          10.0.147.219:6443,169.254.169.2:6443,10.0.242.240:6443
f7fff5d5-5eff-4a40-98b1-3a4ba8f7f69c    Service_default/    tcp        172.30.0.1:443          169.254.169.2:6443,10.0.163.212:6443,10.0.242.240:6443
12fe57a0-50a4-4a1b-ac10-5f288badee07    Service_default/    tcp        172.30.0.1:443          10.0.147.219:6443,10.0.163.212:6443,10.0.242.240:6443
3f137fbf-0b78-4875-ba44-fbf89f254cf7    Service_openshif    tcp        172.30.23.153:443       10.130.0.14:8443
174199fe-0562-4141-b410-12094db922a7    Service_openshif    tcp        172.30.69.51:50051      10.130.0.84:50051
5ee2d4bd-c9e2-4d16-a6df-f54cd17c9ac3    Service_openshif    tcp        172.30.143.87:9001      10.0.145.205:9001,10.0.147.219:9001,10.0.163.212:9001,10.0.165.9:9001,10.0.209.170:9001,10.0.242.240:9001
a056ae3d-83f8-45bc-9c80-ef89bce7b162    Service_openshif    tcp        172.30.164.74:443       10.0.147.219:6443,10.0.163.212:6443,10.0.242.240:6443
bac51f3d-9a6f-4f5e-ac02-28fd343a332a    Service_openshif    tcp        172.30.0.10:53          10.131.0.6:5353
                                                            tcp        172.30.0.10:9154        10.131.0.6:9154
48105bbc-51d7-4178-b975-417433f9c20a    Service_openshif    tcp        172.30.26.159:2379      10.0.147.219:2379,169.254.169.2:2379,10.0.242.240:2379
                                                            tcp        172.30.26.159:9979      10.0.147.219:9979,169.254.169.2:9979,10.0.242.240:9979
7de2b8fc-342a-415f-ac13-1a493f4e39c0    Service_openshif    tcp        172.30.53.219:443       10.128.0.7:8443
                                                            tcp        172.30.53.219:9192      10.128.0.7:9192
2cef36bc-d720-4afb-8d95-9350eff1d27a    Service_openshif    tcp        172.30.81.66:443        10.128.0.23:8443
365cb6fb-e15e-45a4-a55b-21868b3cf513    Service_openshif    tcp        172.30.96.51:50051      10.130.0.19:50051
41691cbb-ec55-4cdb-8431-afce679c5e8d    Service_openshif    tcp        172.30.98.218:9099      169.254.169.2:9099
82df10ba-8143-400b-977a-8f5f416a4541    Service_openshif    tcp        172.30.26.159:2379      10.0.147.219:2379,10.0.163.212:2379,169.254.169.2:2379
                                                            tcp        172.30.26.159:9979      10.0.147.219:9979,10.0.163.212:9979,169.254.169.2:9979
debe7f3a-39a8-490e-bc0a-ebbfafdffb16    Service_openshif    tcp        172.30.23.244:443       10.128.0.48:8443,10.129.0.27:8443,10.130.0.45:8443
8a749239-02d9-4dc2-8737-716528e0da7b    Service_openshif    tcp        172.30.124.255:8443     10.128.0.14:8443
880c7c78-c790-403d-a3cb-9f06592717a3    Service_openshif    tcp        172.30.0.10:53          10.130.0.20:5353
                                                            tcp        172.30.0.10:9154        10.130.0.20:9154
d2f39078-6751-4311-a161-815bbaf7f9c7    Service_openshif    tcp        172.30.26.159:2379      169.254.169.2:2379,10.0.163.212:2379,10.0.242.240:2379
                                                            tcp        172.30.26.159:9979      169.254.169.2:9979,10.0.163.212:9979,10.0.242.240:9979
30948278-602b-455c-934a-28e64c46de12    Service_openshif    tcp        172.30.157.35:9443      10.130.0.43:9443
2cc7e376-7c02-4a82-89e8-dfa1e23fb003    Service_openshif    tcp        172.30.159.212:17698    10.128.0.48:17698,10.129.0.27:17698,10.130.0.45:17698
e7d22d35-61c2-40c2-bc30-265cff8ed18d    Service_openshif    tcp        172.30.143.87:9001      10.0.145.205:9001,10.0.147.219:9001,10.0.163.212:9001,10.0.165.9:9001,10.0.209.170:9001,169.254.169.2:9001
75164e75-e0c5-40fb-9636-bfdbf4223a02    Service_openshif    tcp        172.30.150.68:1936      10.129.4.8:1936,10.131.0.10:1936
                                                            tcp        172.30.150.68:443       10.129.4.8:443,10.131.0.10:443
                                                            tcp        172.30.150.68:80        10.129.4.8:80,10.131.0.10:80
7bc4ee74-dccf-47e9-9149-b011f09aff39    Service_openshif    tcp        172.30.164.74:443       10.0.147.219:6443,10.0.163.212:6443,169.254.169.2:6443
0db59e74-1cc6-470c-bf44-57c520e0aa8f    Service_openshif    tcp        10.0.163.212:31460
                                                            tcp        10.0.163.212:32361
c300e134-018c-49af-9f84-9deb1d0715f8    Service_openshif    tcp        172.30.42.244:50051     10.130.0.47:50051
5e352773-429b-4881-afb3-a13b7ba8b081    Service_openshif    tcp        172.30.244.66:443       10.129.0.8:8443,10.130.0.8:8443
54b82d32-1939-4465-a87d-f26321442a7a    Service_openshif    tcp        172.30.12.9:8443        10.128.0.35:8443

From this truncated output you can see there are many OVN-Kubernetes load balancers. Load balancers in OVN-Kubernetes are representations of services.

Command line arguments for ovn-nbctl to examine northbound database contents

The following table describes the command line arguments that can be used with ovn-nbctl to examine the contents of the northbound database.

Table 1. Command line arguments to examine northbound database contents
Argument	Description
`ovn-nbctl show`	An overview of the northbound database contents.
`ovn-nbctl show <switch_or_router>`	Show the details associated with the specified switch or router.
`ovn-nbctl lr-list`	Show the logical routers.
`ovn-nbctl lrp-list <router>`	Using the router information from `ovn-nbctl lr-list` to show the router ports.
`ovn-nbctl lr-nat-list <router>`	Show network address translation details for the specified router.
`ovn-nbctl ls-list`	Show the logical switches
`ovn-nbctl lsp-list <switch>`	Using the switch information from `ovn-nbctl ls-list` to show the switch port.
`ovn-nbctl lsp-get-type <port>`	Get the type for the logical port.
`ovn-nbctl lb-list`	Show the load balancers.

Listing the OVN-Kubernetes southbound database contents

Logic flow rules are stored in the southbound database that is a representation of your infrastructure. The up to date information is present on the OVN Raft leader and this procedure describes how to find the Raft leader and query it to list the OVN southbound database contents.

Prerequisites

Access to the cluster as a user with the cluster-admin role.
The OpenShift CLI (oc) installed.

Procedure

Find the OVN Raft leader for the southbound database.

The Raft leader stores the most up to date information.

List the pods by running the following command:

$ oc get po -n openshift-ovn-kubernetes

Example output

NAME                   READY   STATUS    RESTARTS       AGE
ovnkube-master-7j97q   6/6     Running   2 (134m ago)   135m
ovnkube-master-gt4ms   6/6     Running   1 (126m ago)   133m
ovnkube-master-mk6p6   6/6     Running   0              134m
ovnkube-node-8qvtr     5/5     Running   0              135m
ovnkube-node-bqztb     5/5     Running   0              117m
ovnkube-node-fqdc9     5/5     Running   0              135m
ovnkube-node-tlfwv     5/5     Running   0              135m
ovnkube-node-wlwkn     5/5     Running   0              128m

Choose one of the master pods at random and run the following command to find the OVN southbound Raft leader:

$ oc exec -n openshift-ovn-kubernetes ovnkube-master-7j97q \
-- /usr/bin/ovn-appctl -t /var/run/ovn/ovnsb_db.ctl \
--timeout=3 cluster/status OVN_Southbound

Example output

Defaulted container "northd" out of: northd, nbdb, kube-rbac-proxy, sbdb, ovnkube-master, ovn-dbchecker
1930
Name: OVN_Southbound
Cluster ID: f772 (f77273c0-7986-42dd-bd3c-a9f18e25701f)
Server ID: 1930 (1930f4b7-314b-406f-9dcb-b81fe2729ae1)
Address: ssl:10.0.147.219:9644
Status: cluster member
Role: follower (1)
Term: 3
Leader: 7081 (2)
Vote: unknown

Election timer: 16000
Log: [2, 2423]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->0000 ->7145 <-7081 <-7145
Disconnections: 0
Servers:
    7081 (7081 at ssl:10.0.163.212:9644) last msg 59 ms ago (3)
    1930 (1930 at ssl:10.0.147.219:9644) (self)
    7145 (7145 at ssl:10.0.242.240:9644) last msg 7871735 ms ago

1	This pod is identified as a follower
2	The leader is identified as `7081`
3	The `7081` is on IP address `10.0.163.212`

Find the ovnkube-master pod running on IP Address 10.0.163.212 using the following command:

$ oc get po -o wide -n openshift-ovn-kubernetes | grep 10.0.163.212 | grep -v ovnkube-node

Example output

ovnkube-master-mk6p6   6/6     Running   0              136m   10.0.163.212   ip-10-0-163-212.ec2.internal   <none>           <none>

The ovnkube-master-mk6p6 pod runs on IP Address 10.0.163.212.

Run the following command to show all the information stored in the southbound database:

$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-mk6p6 \
-c northd -- ovn-sbctl show

Example output

Chassis "8ca57b28-9834-45f0-99b0-96486c22e1be"
    hostname: ip-10-0-156-16.ec2.internal
    Encap geneve
        ip: "10.0.156.16"
        options: {csum="true"}
    Port_Binding k8s-ip-10-0-156-16.ec2.internal
    Port_Binding etor-GR_ip-10-0-156-16.ec2.internal
    Port_Binding jtor-GR_ip-10-0-156-16.ec2.internal
    Port_Binding openshift-ingress-canary_ingress-canary-hsblx
    Port_Binding rtoj-GR_ip-10-0-156-16.ec2.internal
    Port_Binding openshift-monitoring_prometheus-adapter-658fc5967-9l46x
    Port_Binding rtoe-GR_ip-10-0-156-16.ec2.internal
    Port_Binding openshift-multus_network-metrics-daemon-77nvz
    Port_Binding openshift-ingress_router-default-64fd8c67c7-df598
    Port_Binding openshift-dns_dns-default-ttpcq
    Port_Binding openshift-monitoring_alertmanager-main-0
    Port_Binding openshift-e2e-loki_loki-promtail-g2pbh
    Port_Binding openshift-network-diagnostics_network-check-target-m6tn4
    Port_Binding openshift-monitoring_thanos-querier-75b5cf8dcb-qf8qj
    Port_Binding cr-rtos-ip-10-0-156-16.ec2.internal
    Port_Binding openshift-image-registry_image-registry-7b7bc44566-mp9b8

This detailed output shows the chassis and the ports that are attached to the chassis which in this case are all of the router ports and anything that runs like host networking. Any pods communicate out to the wider network using source network address translation (SNAT). Their IP address is translated into the IP address of the node that the pod is running on and then sent out into the network.

In addition to the chassis information the southbound database has all the logic flows and those logic flows are then sent to the ovn-controller running on each of the nodes. The ovn-controller translates the logic flows into open flow rules and ultimately programs OpenvSwitch so that your pods can then follow open flow rules and make it out of the network.

Run the following command to display the options available with the command ovn-sbctl:

$ oc exec -n openshift-ovn-kubernetes -it ovnkube-master-mk6p6 \
-c northd -- ovn-sbctl --help

Command line arguments for ovn-sbctl to examine southbound database contents

The following table describes the command line arguments that can be used with ovn-sbctl to examine the contents of the southbound database.

Table 2. Command line arguments to examine southbound database contents
Argument	Description
`ovn-sbctl show`	Overview of the southbound database contents.
`ovn-sbctl list Port_Binding <port>`	List the contents of southbound database for a the specified port .
`ovn-sbctl dump-flows`	List the logical flows.

OVN-Kubernetes logical architecture

OVN is a network virtualization solution. It creates logical switches and routers. These switches and routers are interconnected to create any network topologies. When you run ovnkube-trace with the log level set to 2 or 5 the OVN-Kubernetes logical components are exposed. The following diagram shows how the routers and switches are connected in OKD.

Figure 2. OVN-Kubernetes router and switch components

The key components involved in packet processing are:

Gateway routers: Gateway routers sometimes called L3 gateway routers, are typically used between the distributed routers and the physical network. Gateway routers including their logical patch ports are bound to a physical location (not distributed), or chassis. The patch ports on this router are known as l3gateway ports in the ovn-southbound database (ovn-sbdb).
Distributed logical routers: Distributed logical routers and the logical switches behind them, to which virtual machines and containers attach, effectively reside on each hypervisor.
Join local switch: Join local switches are used to connect the distributed router and gateway routers. It reduces the number of IP addresses needed on the distributed router.
Logical switches with patch ports: Logical switches with patch ports are used to virtualize the network stack. They connect remote logical ports through tunnels.
Logical switches with localnet ports: Logical switches with localnet ports are used to connect OVN to the physical network. They connect remote logical ports by bridging the packets to directly connected physical L2 segments using localnet ports.
Patch ports: Patch ports represent connectivity between logical switches and logical routers and between peer logical routers. A single connection has a pair of patch ports at each such point of connectivity, one on each side.
l3gateway ports: l3gateway ports are the port binding entries in the ovn-sbdb for logical patch ports used in the gateway routers. They are called l3gateway ports rather than patch ports just to portray the fact that these ports are bound to a chassis just like the gateway router itself.
localnet ports: localnet ports are present on the bridged logical switches that allows a connection to a locally accessible network from each ovn-controller instance. This helps model the direct connectivity to the physical network from the logical switches. A logical switch can only have a single localnet port attached to it.

Installing network-tools on local host

Install network-tools on your local host to make a collection of tools available for debugging OKD cluster network issues.

Procedure

Clone the network-tools repository onto your workstation with the following command:
```
$ git clone git@github.com:openshift/network-tools.git
```
Change into the directory for the repository you just cloned:
```
$ cd network-tools
```
Optional: List all available commands:
```
$ ./debug-scripts/network-tools -h
```

Running network-tools

Get information about the logical switches and routers by running network-tools.

Prerequisites

You installed the OpenShift CLI (oc).
You are logged in to the cluster as a user with cluster-admin privileges.
You have installed network-tools on local host.

Procedure

List the routers by running the following command:

$ ./debug-scripts/network-tools ovn-db-run-command ovn-nbctl lr-list

Example output

Leader pod is ovnkube-master-vslqm
5351ddd1-f181-4e77-afc6-b48b0a9df953 (GR_helix13.lab.eng.tlv2.redhat.com)
ccf9349e-1948-4df8-954e-39fb0c2d4d06 (GR_helix14.lab.eng.tlv2.redhat.com)
e426b918-75a8-4220-9e76-20b7758f92b7 (GR_hlxcl7-master-0.hlxcl7.lab.eng.tlv2.redhat.com)
dded77c8-0cc3-4b99-8420-56cd2ae6a840 (GR_hlxcl7-master-1.hlxcl7.lab.eng.tlv2.redhat.com)
4f6747e6-e7ba-4e0c-8dcd-94c8efa51798 (GR_hlxcl7-master-2.hlxcl7.lab.eng.tlv2.redhat.com)
52232654-336e-4952-98b9-0b8601e370b4 (ovn_cluster_router)

List the localnet ports by running the following command:

$ ./debug-scripts/network-tools ovn-db-run-command \
ovn-sbctl find Port_Binding type=localnet

Example output

Leader pod is ovnkube-master-vslqm
_uuid               : 3de79191-cca8-4c28-be5a-a228f0f9ebfc
additional_chassis  : []
additional_encap    : []
chassis             : []
datapath            : 3f1a4928-7ff5-471f-9092-fe5f5c67d15c
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : br-ex_helix13.lab.eng.tlv2.redhat.com
mac                 : [unknown]
nat_addresses       : []
options             : {network_name=physnet}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 2
type                : localnet
up                  : false
virtual_parent      : []

_uuid               : dbe21daf-9594-4849-b8f0-5efbfa09a455
additional_chassis  : []
additional_encap    : []
chassis             : []
datapath            : db2a6067-fe7c-4d11-95a7-ff2321329e11
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : br-ex_hlxcl7-master-2.hlxcl7.lab.eng.tlv2.redhat.com
mac                 : [unknown]
nat_addresses       : []
options             : {network_name=physnet}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 2
type                : localnet
up                  : false
virtual_parent      : []

[...]

List the l3gateway ports by running the following command:

$ ./debug-scripts/network-tools ovn-db-run-command \
ovn-sbctl find Port_Binding type=l3gateway

Example output

Leader pod is ovnkube-master-vslqm
_uuid               : 9314dc80-39e1-4af7-9cc0-ae8a9708ed59
additional_chassis  : []
additional_encap    : []
chassis             : 336a923d-99e8-4e71-89a6-12564fde5760
datapath            : db2a6067-fe7c-4d11-95a7-ff2321329e11
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : etor-GR_hlxcl7-master-2.hlxcl7.lab.eng.tlv2.redhat.com
mac                 : ["52:54:00:3e:95:d3"]
nat_addresses       : ["52:54:00:3e:95:d3 10.46.56.77"]
options             : {l3gateway-chassis="7eb1f1c3-87c2-4f68-8e89-60f5ca810971", peer=rtoe-GR_hlxcl7-master-2.hlxcl7.lab.eng.tlv2.redhat.com}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 1
type                : l3gateway
up                  : true
virtual_parent      : []

_uuid               : ad7eb303-b411-4e9f-8d36-d07f1f268e27
additional_chassis  : []
additional_encap    : []
chassis             : f41453b8-29c5-4f39-b86b-e82cf344bce4
datapath            : 082e7a60-d9c7-464b-b6ec-117d3426645a
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : etor-GR_helix14.lab.eng.tlv2.redhat.com
mac                 : ["34:48:ed:f3:e2:2c"]
nat_addresses       : ["34:48:ed:f3:e2:2c 10.46.56.14"]
options             : {l3gateway-chassis="2e8abe3a-cb94-4593-9037-f5f9596325e2", peer=rtoe-GR_helix14.lab.eng.tlv2.redhat.com}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 1
type                : l3gateway
up                  : true
virtual_parent      : []

[...]

List the patch ports by running the following command:

$ ./debug-scripts/network-tools ovn-db-run-command \
ovn-sbctl find Port_Binding type=patch

Example output

Leader pod is ovnkube-master-vslqm
_uuid               : c48b1380-ff26-4965-a644-6bd5b5946c61
additional_chassis  : []
additional_encap    : []
chassis             : []
datapath            : 72734d65-fae1-4bd9-a1ee-1bf4e085a060
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : jtor-ovn_cluster_router
mac                 : [router]
nat_addresses       : []
options             : {peer=rtoj-ovn_cluster_router}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 4
type                : patch
up                  : false
virtual_parent      : []

_uuid               : 5df51302-f3cd-415b-a059-ac24389938f7
additional_chassis  : []
additional_encap    : []
chassis             : []
datapath            : 0551c90f-e891-4909-8e9e-acc7909e06d0
encap               : []
external_ids        : {}
gateway_chassis     : []
ha_chassis_group    : []
logical_port        : rtos-hlxcl7-master-1.hlxcl7.lab.eng.tlv2.redhat.com
mac                 : ["0a:58:0a:82:00:01 10.130.0.1/23"]
nat_addresses       : []
options             : {chassis-redirect-port=cr-rtos-hlxcl7-master-1.hlxcl7.lab.eng.tlv2.redhat.com, peer=stor-hlxcl7-master-1.hlxcl7.lab.eng.tlv2.redhat.com}
parent_port         : []
port_security       : []
requested_additional_chassis: []
requested_chassis   : []
tag                 : []
tunnel_key          : 4
type                : patch
up                  : false
virtual_parent      : []

[...]

Introduction to OVN-Kubernetes architecture

Listing all resources in the OVN-Kubernetes project

Listing the OVN-Kubernetes northbound database contents

Command line arguments for ovn-nbctl to examine northbound database contents

Listing the OVN-Kubernetes southbound database contents

Command line arguments for ovn-sbctl to examine southbound database contents

OVN-Kubernetes logical architecture

Installing network-tools on local host

Running network-tools

Additional resources