diff --git a/openstack/networking/v2/extensions/layer3/routers/requests_test.go b/openstack/networking/v2/extensions/layer3/routers/requests_test.go
index 56a0d74..961354c 100755
--- a/openstack/networking/v2/extensions/layer3/routers/requests_test.go
+++ b/openstack/networking/v2/extensions/layer3/routers/requests_test.go
@@ -288,6 +288,17 @@
 	th.AssertEquals(t, "9a83fa11-8da5-436e-9afe-3d3ac5ce7770", res.ID)
 }
 
+func TestAddInterfaceRequiredOpts(t *testing.T) {
+	_, err := AddInterface(fake.ServiceClient(), "foo", InterfaceOpts{}).Extract()
+	if err == nil {
+		t.Fatalf("Expected error, got none")
+	}
+	_, err = AddInterface(fake.ServiceClient(), "foo", InterfaceOpts{SubnetID: "bar", PortID: "baz"}).Extract()
+	if err == nil {
+		t.Fatalf("Expected error, got none")
+	}
+}
+
 func TestRemoveInterface(t *testing.T) {
 	th.SetupHTTP()
 	defer th.TeardownHTTP()
diff --git a/openstack/networking/v2/extensions/layer3/routers/results.go b/openstack/networking/v2/extensions/layer3/routers/results.go
index d14578c..2fc27fe 100755
--- a/openstack/networking/v2/extensions/layer3/routers/results.go
+++ b/openstack/networking/v2/extensions/layer3/routers/results.go
@@ -53,12 +53,8 @@
 // the end of a page and the pager seeks to traverse over a new one. In order
 // to do this, it needs to construct the next page's URL.
 func (p RouterPage) NextPageURL() (string, error) {
-	type link struct {
-		Href string `mapstructure:"href"`
-		Rel  string `mapstructure:"rel"`
-	}
 	type resp struct {
-		Links []link `mapstructure:"routers_links"`
+		Links []gophercloud.Link `mapstructure:"routers_links"`
 	}
 
 	var r resp
@@ -67,17 +63,7 @@
 		return "", err
 	}
 
-	var url string
-	for _, l := range r.Links {
-		if l.Rel == "next" {
-			url = l.Href
-		}
-	}
-	if url == "" {
-		return "", nil
-	}
-
-	return url, nil
+	return gophercloud.ExtractNextURL(r.Links)
 }
 
 // IsEmpty checks whether a RouterPage struct is empty.