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60 lines
4.4 KiB
Plaintext
60 lines
4.4 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * microshift_networking/microshift-cni.adoc
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:_mod-docs-content-type: CONCEPT
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[id="microshift-network-topology_{context}"]
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= Network topology
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[role="_abstract"]
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OVN-Kubernetes provides an overlay-based networking implementation. This overlay includes an OVS-based implementation of `Service` and `NetworkPolicy` resources.
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The overlay network uses the Geneve (Generic Network Virtualization Encapsulation) tunnel protocol. The pod maximum transmission unit (MTU) for the Geneve tunnel is set to the default route MTU if it is not configured.
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To configure the MTU, you must set an equal-to or less-than value than the MTU of the physical interface on the host. A less-than value for the MTU makes room for the required information that is added to the tunnel header before it is transmitted.
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[IMPORTANT]
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====
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The MTU value of the OVN overlay networking in {microshift-short} must be 100 bytes smaller than the MTU value of the base network. If no MTU value is configured, {microshift-short} autoconfigures the value using the MTU value of the default gateway (Internet Protocol version 4 (IPv4) or Internet Protocol version 6 (IPv6)) of the host. If the auto-configuration does not work correctly, the MTU value can be configured manually. For example, if the MTU value of the network is `9000`, the OVN MTU size must be set to `8900`.
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====
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OVS runs as a systemd service on the {microshift-short} node. The OVS RPM package is installed as a dependency to the `microshift-networking` RPM package. OVS starts immediately when the `microshift-networking` RPM is installed.
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.{product-title} network topology
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image:317_RHbM_OVN_topology_0923.png[title="{microshift-short} uses an overlay-based networking implementation, details follow."]
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[id="microshift-description-ovn-logical-components_{context}"]
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== Description of the OVN logical components of the virtualized network
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OVN node switch::
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A virtual switch named `<node-name>`. The OVN node switch is named according to the hostname of the node.
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** In this example, the `node-name` is `microshift-dev`.
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OVN cluster router::
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A virtual router named `ovn_cluster_router`, also known as the distributed router.
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** In this example, the node network is `10.42.0.0/16`.
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OVN join switch::
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A virtual switch named `join`.
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OVN gateway router::
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A virtual router named `GR_<node-name>`, also known as the external gateway router.
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OVN external switch::
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A virtual switch named `ext_<node-name>.`
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[id="microshift-description-connections-network-topology_{context}"]
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== Description of the connections in the network topology figure
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* The north-south traffic between the network service and the OVN external switch `ext_microshift-dev` is provided through the host kernel by the gateway bridge `br-ex`.
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* The OVN gateway router `GR_microshift-dev` is connected to the external network switch `ext_microshift-dev` through the logical router port 4. Port 4 is attached with the node IP address 192.168.122.14.
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* The join switch `join` connects the OVN gateway router `GR_microshift-dev` to the OVN cluster router `ovn_cluster_router`. The IP address range is 100.62.0.0/16.
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** The OVN gateway router `GR_microshift-dev` connects to the OVN join switch `join` through the logical router port 3. Port 3 attaches with the internal IP address 100.64.0.2.
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** The OVN cluster router `ovn_cluster_router` connects to the join switch `join` through the logical router port 2. Port 2 attaches with the internal IP address 100.64.0.1.
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* The OVN cluster router `ovn_cluster_router` connects to the node switch `microshift-dev` through the logical router port 1. Port 1 is attached with the OVN cluster network IP address 10.42.0.1.
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* The east-west traffic between the pods and the network service is provided by the OVN cluster router `ovn_cluster_router` and the node switch `microshift-dev`. The IP address range is 10.42.0.0/24.
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* The east-west traffic between pods is provided by the node switch `microshift-dev` without network address translation (NAT).
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* The north-south traffic between the pods and the external network is provided by the OVN cluster router `ovn_cluster_router` and the host network. This router is connected through the `ovn-kubernetes` management port `ovn-k8s-mp0`, with the IP address 10.42.0.2.
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* All the pods are connected to the OVN node switch through their interfaces.
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** In this example, Pod 1 and Pod 2 are connected to the node switch through `Interface 1` and `Interface 2`.
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