diff --git a/specification/vmware/resource-manager/Microsoft.AVS/stable/2020-03-20/vmware.json b/specification/vmware/resource-manager/Microsoft.AVS/stable/2020-03-20/vmware.json
index cec614376448..d77f644da606 100644
--- a/specification/vmware/resource-manager/Microsoft.AVS/stable/2020-03-20/vmware.json
+++ b/specification/vmware/resource-manager/Microsoft.AVS/stable/2020-03-20/vmware.json
@@ -1785,7 +1785,11 @@
         },
         "networkBlock": {
           "description": "The block of addresses should be unique across VNet in your subscription as well as on-premise. Make sure the CIDR format is conformed to (A.B.C.D/X) where A,B,C,D are between 0 and 255, and X is between 0 and 22",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "managementNetwork": {
           "description": "Network used to access vCenter Server and NSX-T Manager",
diff --git a/specification/vmware/resource-manager/Microsoft.AVS/stable/2021-06-01/vmware.json b/specification/vmware/resource-manager/Microsoft.AVS/stable/2021-06-01/vmware.json
index 9e300148abd8..a0f3f952b1d3 100644
--- a/specification/vmware/resource-manager/Microsoft.AVS/stable/2021-06-01/vmware.json
+++ b/specification/vmware/resource-manager/Microsoft.AVS/stable/2021-06-01/vmware.json
@@ -5197,7 +5197,11 @@
         },
         "networkBlock": {
           "description": "The block of addresses should be unique across VNet in your subscription as well as on-premise. Make sure the CIDR format is conformed to (A.B.C.D/X) where A,B,C,D are between 0 and 255, and X is between 0 and 22",
-          "type": "string"
+          "type": "string",
+          "x-ms-mutability": [
+            "create",
+            "read"
+          ]
         },
         "managementNetwork": {
           "description": "Network used to access vCenter Server and NSX-T Manager",