diff --git a/pkg/agent/flannel/setup_test.go b/pkg/agent/flannel/setup_test.go
new file mode 100644
index 00000000000..32a9368f7a2
--- /dev/null
+++ b/pkg/agent/flannel/setup_test.go
@@ -0,0 +1,83 @@
+package flannel
+
+import (
+	"io/ioutil"
+	"net"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/rancher/k3s/pkg/daemons/config"
+)
+
+func stringToCIDR(s string) []*net.IPNet {
+	var netCidrs []*net.IPNet
+	for _, v := range strings.Split(s, ",") {
+		_, parsed, _ := net.ParseCIDR(v)
+		netCidrs = append(netCidrs, parsed)
+	}
+	return netCidrs
+}
+
+func Test_findNetMode(t *testing.T) {
+	tests := []struct {
+		name    string
+		args    string
+		want    int
+		wantErr bool
+	}{
+		{"dual-stack", "10.42.0.0/16,2001:cafe:22::/56", ipv4 + ipv6, false},
+		{"ipv4 only", "10.42.0.0/16", ipv4, false},
+		{"ipv6 only", "2001:cafe:42:0::/56", ipv6, false},
+		{"wrong input", "wrong", 0, true},
+	}
+	for _, tt := range tests {
+
+		t.Run(tt.name, func(t *testing.T) {
+			netCidrs := stringToCIDR(tt.args)
+			got, err := findNetMode(netCidrs)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("findNetMode() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("findNetMode() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_createFlannelConf(t *testing.T) {
+	tests := []struct {
+		name       string
+		args       string
+		wantConfig []string
+		wantErr    bool
+	}{
+		{"dual-stack", "10.42.0.0/16,2001:cafe:22::/56", []string{"\"Network\": \"10.42.0.0/16\"", "\"IPv6Network\": \"2001:cafe:22::/56\"", "\"EnableIPv6\": true"}, false},
+		{"ipv4 only", "10.42.0.0/16", []string{"\"Network\": \"10.42.0.0/16\"", "\"IPv6Network\": \"::/0\"", "\"EnableIPv6\": false"}, false},
+	}
+	var containerd = config.Containerd{}
+	for _, tt := range tests {
+		var agent = config.Agent{}
+		agent.ClusterCIDR = stringToCIDR(tt.args)[0]
+		agent.ClusterCIDRs = stringToCIDR(tt.args)
+		var nodeConfig = &config.Node{Docker: false, ContainerRuntimeEndpoint: "", NoFlannel: false, SELinux: false, FlannelBackend: "vxlan", FlannelConf: "test_file", FlannelConfOverride: false, FlannelIface: nil, Containerd: containerd, Images: "", AgentConfig: agent, Token: "", Certificate: nil, ServerHTTPSPort: 0}
+
+		t.Run(tt.name, func(t *testing.T) {
+			if err := createFlannelConf(nodeConfig); (err != nil) != tt.wantErr {
+				t.Errorf("createFlannelConf() error = %v, wantErr %v", err, tt.wantErr)
+			}
+			data, err := ioutil.ReadFile("test_file")
+			if err != nil {
+				t.Errorf("Something went wrong when reading the flannel config file")
+			}
+			for _, config := range tt.wantConfig {
+				isExist, _ := regexp.Match(config, data)
+				if !isExist {
+					t.Errorf("Config is wrong, %s is not present", config)
+				}
+			}
+		})
+	}
+}
diff --git a/pkg/cli/server/server.go b/pkg/cli/server/server.go
index 9baa5b20aab..c76fe6ee2c3 100644
--- a/pkg/cli/server/server.go
+++ b/pkg/cli/server/server.go
@@ -467,8 +467,8 @@ func validateNetworkConfiguration(serverConfig server.Config) error {
 		return errors.Wrap(err, "failed to validate cluster-dns")
 	}
 
-	if (serverConfig.ControlConfig.FlannelBackend != "none" || serverConfig.ControlConfig.DisableNPC == false) && (dualCluster || dualService) {
-		return errors.New("flannel CNI and network policy enforcement are not compatible with dual-stack operation; server must be restarted with --flannel-backend=none --disable-network-policy and an alternative CNI plugin deployed")
+	if (serverConfig.ControlConfig.DisableNPC == false) && (dualCluster || dualService) {
+		return errors.New("network policy enforcement is not compatible with dual-stack operation; server must be restarted with --disable-network-policy")
 	}
 	if dualDNS == true {
 		return errors.New("dual-stack cluster-dns is not supported")
diff --git a/tests/integration/dual_stack_int_test.go b/tests/integration/dual_stack_int_test.go
new file mode 100644
index 00000000000..44607707a0d
--- /dev/null
+++ b/tests/integration/dual_stack_int_test.go
@@ -0,0 +1,55 @@
+package integration
+
+import (
+	"strings"
+	"testing"
+
+	. "github.com/onsi/ginkgo"
+	"github.com/onsi/ginkgo/reporters"
+	. "github.com/onsi/gomega"
+	testutil "github.com/rancher/k3s/tests/util"
+)
+
+var dualStackServerArgs = []string{"--cluster-init", "--cluster-cidr 10.42.0.0/16,2001:cafe:42:0::/56", "--service-cidr 10.43.0.0/16,2001:cafe:42:1::/112"}
+var _ = BeforeSuite(func() {
+	if !testutil.IsExistingServer() {
+		var err error
+		server, err = testutil.K3sStartServer(dualStackServerArgs...)
+		Expect(err).ToNot(HaveOccurred())
+	}
+})
+
+var _ = Describe("dual stack", func() {
+	BeforeEach(func() {
+		if testutil.IsExistingServer() && !testutil.ServerArgsPresent(dualStackServerArgs) {
+			Skip("Test needs k3s server with: " + strings.Join(dualStackServerArgs, " "))
+		}
+	})
+	When("a ipv4 and ipv6 cidr is present", func() {
+		It("starts up with no problems", func() {
+			Eventually(func() (string, error) {
+				return testutil.K3sCmd("kubectl", "get", "pods", "-A")
+			}, "90s", "1s").Should(MatchRegexp("kube-system.+traefik.+1\\/1.+Running"))
+		})
+		It("creates pods with two IPs", func() {
+			podname, err := testutil.K3sCmd("kubectl", "get", "pods", "-nkube-system", "-ojsonpath={.items[?(@.metadata.labels.app\\.kubernetes\\.io/name==\"traefik\")].metadata.name}")
+			Expect(err).NotTo(HaveOccurred())
+			result, err := testutil.K3sCmd("kubectl", "exec", podname, "-nkube-system", "--", "ip", "a")
+			Expect(result).To(ContainSubstring("2001:cafe:42:"))
+			Expect(err).NotTo(HaveOccurred())
+		})
+	})
+})
+
+var _ = AfterSuite(func() {
+	if !testutil.IsExistingServer() {
+		Expect(testutil.K3sKillServer(server)).To(Succeed())
+	}
+})
+
+func Test_IntegrationDualStack(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecsWithDefaultAndCustomReporters(t, "Dual-Stack Suite", []Reporter{
+		reporters.NewJUnitReporter("/tmp/results/junit-ls.xml"),
+	})
+}