diff --git a/scripts/install-cni.sh b/scripts/install-cni.sh
index bc087feb5..6e88d7bc3 100755
--- a/scripts/install-cni.sh
+++ b/scripts/install-cni.sh
@@ -107,8 +107,12 @@ if [ "${MIGRATE_TO_DPV2:-}" == "true" ]; then
 fi
 
 if [ "${ENABLE_CILIUM_PLUGIN}" == "true" ]; then
-  echo "Adding Cilium plug-in to the CNI config."
-  cni_spec=${cni_spec//@cniCiliumPlugin/, {\"type\": \"cilium-cni\", \"enable-route-mtu\": true\}}
+  cilium_cni_config='{"type": "cilium-cni", "enable-route-mtu": true}'
+  if [[ -n "${CILIUM_FAST_START_NAMESPACES:-}" ]]; then
+    cilium_cni_config=$(jq --arg namespaces "${CILIUM_FAST_START_NAMESPACES:-}" '.["fast-start-namespaces"] = $namespaces' <<<"${cilium_cni_config}")
+  fi
+  echo "Adding Cilium plug-in to the CNI config: '$(jq -c . <<<"${cilium_cni_config}")'"
+  cni_spec=${cni_spec//@cniCiliumPlugin/, ${cilium_cni_config}}
 else
   echo "Not using Cilium plug-in."
   cni_spec=${cni_spec//@cniCiliumPlugin/}
diff --git a/scripts/testcase/testcase-cilium-faststart.sh b/scripts/testcase/testcase-cilium-faststart.sh
new file mode 100644
index 000000000..2a768b68d
--- /dev/null
+++ b/scripts/testcase/testcase-cilium-faststart.sh
@@ -0,0 +1,69 @@
+export KUBERNETES_SERVICE_HOST=kubernetes.default.svc
+export KUBERNETES_SERVICE_PORT=443
+
+export ENABLE_CALICO_NETWORK_POLICY=false
+export ENABLE_BANDWIDTH_PLUGIN=false
+export ENABLE_CILIUM_PLUGIN=true
+export CILIUM_HEALTHZ_PORT=63197
+export CILIUM_FAST_START_NAMESPACES=default,kube-system
+export ENABLE_MASQUERADE=false
+export ENABLE_IPV6=false
+
+CNI_SPEC_TEMPLATE=$(cat testdata/spec-template.json)
+export CNI_SPEC_TEMPLATE
+
+function before_test() {
+
+  function curl() {
+    # shellcheck disable=SC2317
+    case "$*" in
+      *http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0*)
+        echo '{"ipv6s": ["2600:1900:4000:318:0:7:0:0"]}'
+        ;;
+      *https://kubernetes.default.svc:443/api/v1/nodes/*)
+        echo '{
+                "metadata": {
+                  "labels": {
+                  },
+                  "creationTimestamp": "2024-01-03T11:54:01Z",
+                  "name": "gke-my-cluster-default-pool-128bc25d-9c94",
+                  "resourceVersion": "891003",
+                  "uid": "f2353a2f-ca8c-4ca0-8dd3-ad1f964a54f0"
+                },
+                "spec": {
+                  "podCIDR": "10.52.1.0/24",
+                  "podCIDRs": [
+                    "10.52.1.0/24"
+                  ],
+                  "providerID": "gce://my-gke-project/us-central1-c/gke-my-cluster-default-pool-128bc25d-9c94"
+                }
+              }'
+        ;;
+      *http://localhost:63197/*)
+        echo 'healthz'
+        ;;
+      *)
+        #unsupported
+        exit 1
+    esac
+  }
+  export -f curl
+
+}
+
+function verify() {
+  local expected
+  local actual
+
+  expected=$(jq -S . <"testdata/expected-cilium-faststart.json")
+  actual=$(jq -S . <"/host/etc/cni/net.d/${CNI_SPEC_NAME}")
+
+  if [ "$expected" != "$actual" ] ; then
+    echo "Expected cni_spec value:"
+    echo "$expected"
+    echo "but actual was"
+    echo "$actual"
+    return 1
+  fi
+
+}
diff --git a/scripts/testcase/testcase-cilium.sh b/scripts/testcase/testcase-cilium.sh
new file mode 100644
index 000000000..d97e2c576
--- /dev/null
+++ b/scripts/testcase/testcase-cilium.sh
@@ -0,0 +1,69 @@
+export KUBERNETES_SERVICE_HOST=kubernetes.default.svc
+export KUBERNETES_SERVICE_PORT=443
+
+export ENABLE_CALICO_NETWORK_POLICY=false
+export ENABLE_BANDWIDTH_PLUGIN=false
+export ENABLE_CILIUM_PLUGIN=true
+export CILIUM_HEALTHZ_PORT=63197
+export CILIUM_FAST_START_NAMESPACES=
+export ENABLE_MASQUERADE=false
+export ENABLE_IPV6=false
+
+CNI_SPEC_TEMPLATE=$(cat testdata/spec-template.json)
+export CNI_SPEC_TEMPLATE
+
+function before_test() {
+
+  function curl() {
+    # shellcheck disable=SC2317
+    case "$*" in
+      *http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0*)
+        echo '{"ipv6s": ["2600:1900:4000:318:0:7:0:0"]}'
+        ;;
+      *https://kubernetes.default.svc:443/api/v1/nodes/*)
+        echo '{
+                "metadata": {
+                  "labels": {
+                  },
+                  "creationTimestamp": "2024-01-03T11:54:01Z",
+                  "name": "gke-my-cluster-default-pool-128bc25d-9c94",
+                  "resourceVersion": "891003",
+                  "uid": "f2353a2f-ca8c-4ca0-8dd3-ad1f964a54f0"
+                },
+                "spec": {
+                  "podCIDR": "10.52.1.0/24",
+                  "podCIDRs": [
+                    "10.52.1.0/24"
+                  ],
+                  "providerID": "gce://my-gke-project/us-central1-c/gke-my-cluster-default-pool-128bc25d-9c94"
+                }
+              }'
+        ;;
+      *http://localhost:63197/*)
+        echo 'healthz'
+        ;;
+      *)
+        #unsupported
+        exit 1
+    esac
+  }
+  export -f curl
+
+}
+
+function verify() {
+  local expected
+  local actual
+
+  expected=$(jq -S . <"testdata/expected-cilium.json")
+  actual=$(jq -S . <"/host/etc/cni/net.d/${CNI_SPEC_NAME}")
+
+  if [ "$expected" != "$actual" ] ; then
+    echo "Expected cni_spec value:"
+    echo "$expected"
+    echo "but actual was"
+    echo "$actual"
+    return 1
+  fi
+
+}
diff --git a/scripts/testdata/expected-cilium-faststart.json b/scripts/testdata/expected-cilium-faststart.json
new file mode 100644
index 000000000..26dac36db
--- /dev/null
+++ b/scripts/testdata/expected-cilium-faststart.json
@@ -0,0 +1,29 @@
+{
+  "name": "gke-pod-network",
+  "cniVersion": "0.3.1",
+  "plugins": [
+    {
+      "type": "ptp",
+      "mtu": 1460,
+      "ipam": {
+        "type": "host-local",
+        "ranges": [
+          [{"subnet": "10.52.1.0/24"}]
+        ],
+        "routes": [
+          {"dst": "0.0.0.0/0"}
+        ]
+      }
+    },
+    {
+      "type": "portmap",
+      "capabilities": {
+        "portMappings": true
+      }
+    }, {
+      "type": "cilium-cni",
+      "enable-route-mtu": true,
+      "fast-start-namespaces": "default,kube-system"
+    }
+  ]
+}
diff --git a/scripts/testdata/expected-cilium.json b/scripts/testdata/expected-cilium.json
new file mode 100644
index 000000000..21640ce5c
--- /dev/null
+++ b/scripts/testdata/expected-cilium.json
@@ -0,0 +1,28 @@
+{
+  "name": "gke-pod-network",
+  "cniVersion": "0.3.1",
+  "plugins": [
+    {
+      "type": "ptp",
+      "mtu": 1460,
+      "ipam": {
+        "type": "host-local",
+        "ranges": [
+          [{"subnet": "10.52.1.0/24"}]
+        ],
+        "routes": [
+          {"dst": "0.0.0.0/0"}
+        ]
+      }
+    },
+    {
+      "type": "portmap",
+      "capabilities": {
+        "portMappings": true
+      }
+    }, {
+      "type": "cilium-cni",
+      "enable-route-mtu": true
+    }
+  ]
+}