diff --git a/images/504_OpenShift_UDN_L2_0325.png b/images/504_OpenShift_UDN_L2_0325.png new file mode 100644 index 0000000000..999d72c42e Binary files /dev/null and b/images/504_OpenShift_UDN_L2_0325.png differ diff --git a/modules/nw-udn-best-practices.adoc b/modules/nw-udn-best-practices.adoc index 98882df024..ee7d280c12 100644 --- a/modules/nw-udn-best-practices.adoc +++ b/modules/nw-udn-best-practices.adoc @@ -43,6 +43,3 @@ Before setting up a `UserDefinedNetwork` custom resource (CR), you should consid * The cluster subnet and services CIDR for a `UserDefinedNetwork` CR cannot overlap with the default cluster subnet CIDR. OVN-Kubernetes network plugin uses `100.64.0.0/16` as the default join subnet for the network. You must not use that value to configure a `UserDefinedNetwork` CR's `joinSubnets` field. If the default address values are used anywhere in the network for the cluster you must override the default values by setting the `joinSubnets` field. For more information, see "Additional configuration details for user-defined networks". -* A layer 2 topology creates a virtual switch that is distributed across all nodes in a cluster. Virtual machines and pods connect to this virtual switch so that all these components can communicate with each other within the same subnet. If you decide not to specify a layer 2 subnet, then you must manually configure IP addresses for each pod in your cluster. When not specifying a layer 2 subnet, port security is limited to preventing Media Access Control (MAC) spoofing only, and does not include IP spoofing. A layer 2 topology creates a single broadcast domain that can be challenging in large network environments, whereby the topology might cause a broadcast storm that can degrade network performance. - -* A layer 3 topology creates a unique layer 2 segment for each node in a cluster. The layer 3 routing mechanism interconnects these segments so that virtual machines and pods that are hosted on different nodes can communicate with each other. A layer 3 topology can effectively manage large broadcast domains by assigning each domain to a specific node, so that broadcast traffic has a reduced scope. To configure a layer 3 topology, you must configure `cidr` and `hostSubnet` parameters. diff --git a/modules/nw-udn-l2-l3.adoc b/modules/nw-udn-l2-l3.adoc new file mode 100644 index 0000000000..4117ea664a --- /dev/null +++ b/modules/nw-udn-l2-l3.adoc @@ -0,0 +1,20 @@ +//module included in the following assembly: +// +// *networking/multiple_networks/about-user-defined-networks.adoc +:_mod-docs-content-type: REFERENCE +[id="nw-udn-l2-l3_{context}"] += Layer 2 and layer 3 topologies + +A layer 2 topology creates a virtual switch that is distributed across all nodes in a cluster. Virtual machines and pods connect to this virtual switch so that all these components can communicate with each other within the same subnet. If you decide not to specify a layer 2 subnet, then you must manually configure IP addresses for each pod in your cluster. When you do not specify a layer 2 subnet, port security is limited to preventing Media Access Control (MAC) spoofing only, and does not include IP spoofing. A layer 2 topology creates a single broadcast domain that can be challenging in large network environments, where the topology might cause a broadcast storm that can degrade network performance. + +The following diagram shows two nodes that use an UDN with a layer 2 topology to live migrate a pod from `Node 1` to `Node 2`. Each node includes two interfaces: + +* A node interface, which is a compute node that connects networking components to the node. +* An Open vSwitch (OVS) bridge such as `br-ex`, which creates an layer 2 OVN switch so that pods can communicate with each other and share resources. + +An external switch connects these two interfaces, while the gateway or router handles routing traffic between the external switch and the layer 2 OVN switch. Pods in a node can use the UDN to communicate with each other. The layer 2 OVN switch handles node traffic over UDN so that live migrate of a pod from one node to another is possible. + +.A user-defined network (UDN) that uses a layer 2 topology +image::504_OpenShift_UDN_L2_0325.png[A UDN that uses a layer 2 topology for migrating a pod from node-1 to node-2] + +A layer 3 topology creates a unique layer 2 segment for each node in a cluster. The layer 3 routing mechanism interconnects these segments so that virtual machines and pods that are hosted on different nodes can communicate with each other. A layer 3 topology can effectively manage large broadcast domains by assigning each domain to a specific node, so that broadcast traffic has a reduced scope. To configure a layer 3 topology, you must configure `cidr` and `hostSubnet` parameters. \ No newline at end of file diff --git a/networking/multiple_networks/primary_networks/about-user-defined-networks.adoc b/networking/multiple_networks/primary_networks/about-user-defined-networks.adoc index 458d9edb37..2b05180b6f 100644 --- a/networking/multiple_networks/primary_networks/about-user-defined-networks.adoc +++ b/networking/multiple_networks/primary_networks/about-user-defined-networks.adoc @@ -27,6 +27,9 @@ include::modules/nw-udn-benefits.adoc[leveloffset=+1] //Limitations that users should consider for UDN. include::modules/nw-udn-limitations.adoc[leveloffset=+1] +// Layer 2 and layer 3 topologies +include::modules/nw-udn-l2-l3.adoc[leveloffset=+1] + //About CUDN CR include::modules/nw-cudn-about.adoc[leveloffset=+1]