diff --git a/crd/overlayextensionconfig/api/v1alpha1/overlayextensionconfig_types.go b/crd/overlayextensionconfig/api/v1alpha1/overlayextensionconfig_types.go
index c3d256e5d..9d5d220d5 100644
--- a/crd/overlayextensionconfig/api/v1alpha1/overlayextensionconfig_types.go
+++ b/crd/overlayextensionconfig/api/v1alpha1/overlayextensionconfig_types.go
@@ -31,9 +31,13 @@ type OverlayExtensionConfigList struct {
 }
 
 // OverlayExtensionConfigSpec defines the desired state of OverlayExtensionConfig.
+// +kubebuilder:validation:XValidation:rule="!has(oldSelf.extensionIPRange) || has(self.extensionIPRange)", message="ExtensionIPRange is required once set"
 type OverlayExtensionConfigSpec struct {
 	// ExtensionIPRange field defines a CIDR that should be able to reach routing domain ip addresses.
 	// +kubebuilder:validation:Optional
+	// +kubebuilder:validation:XValidation:rule="self == oldSelf",message="Value is immutable"
+	// +kubebuilder:validation:MaxLength=43
+	// 43 is max length of IPv6 CIDR string
 	ExtensionIPRange string `json:"extensionIPRange,omitempty"`
 }
 
diff --git a/crd/overlayextensionconfig/manifests/acn.azure.com_overlayextensionconfigs.yaml b/crd/overlayextensionconfig/manifests/acn.azure.com_overlayextensionconfigs.yaml
index 54412ff97..418691c2a 100644
--- a/crd/overlayextensionconfig/manifests/acn.azure.com_overlayextensionconfigs.yaml
+++ b/crd/overlayextensionconfig/manifests/acn.azure.com_overlayextensionconfigs.yaml
@@ -48,10 +48,18 @@ spec:
             description: OverlayExtensionConfigSpec defines the desired state of OverlayExtensionConfig.
             properties:
               extensionIPRange:
-                description: ExtensionIPRange field defines a CIDR that should be
-                  able to reach routing domain ip addresses.
+                description: |-
+                  ExtensionIPRange field defines a CIDR that should be able to reach routing domain ip addresses.
+                  43 is max length of IPv6 CIDR string
+                maxLength: 43
                 type: string
+                x-kubernetes-validations:
+                - message: Value is immutable
+                  rule: self == oldSelf
             type: object
+            x-kubernetes-validations:
+            - message: ExtensionIPRange is required once set
+              rule: '!has(oldSelf.extensionIPRange) || has(self.extensionIPRange)'
           status:
             description: OverlayExtensionConfigStatus defines the observed state of
               OverlayExtensionConfig