diff --git a/routes_test.go b/routes_test.go
index 2560898e..8d98cebc 100644
--- a/routes_test.go
+++ b/routes_test.go
@@ -2,6 +2,7 @@ package headscale
 
 import (
 	"net/netip"
+	"time"
 
 	"gopkg.in/check.v1"
 	"tailscale.com/tailcfg"
@@ -150,7 +151,7 @@ func (s *Suite) TestIsUniquePrefix(c *check.C) {
 		RoutableIPs: []netip.Prefix{route, route2},
 	}
 	machine1 := Machine{
-		ID:             0,
+		ID:             1,
 		MachineKey:     "foo",
 		NodeKey:        "bar",
 		DiscoKey:       "faa",
@@ -175,7 +176,7 @@ func (s *Suite) TestIsUniquePrefix(c *check.C) {
 		RoutableIPs: []netip.Prefix{route2},
 	}
 	machine2 := Machine{
-		ID:             0,
+		ID:             2,
 		MachineKey:     "foo",
 		NodeKey:        "bar",
 		DiscoKey:       "faa",
@@ -209,3 +210,145 @@ func (s *Suite) TestIsUniquePrefix(c *check.C) {
 	c.Assert(err, check.IsNil)
 	c.Assert(len(routes), check.Equals, 0)
 }
+
+func (s *Suite) TestSubnetFailover(c *check.C) {
+	namespace, err := app.CreateNamespace("test")
+	c.Assert(err, check.IsNil)
+
+	pak, err := app.CreatePreAuthKey(namespace.Name, false, false, nil, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = app.GetMachine("test", "test_enable_route_machine")
+	c.Assert(err, check.NotNil)
+
+	prefix, err := netip.ParsePrefix(
+		"10.0.0.0/24",
+	)
+	c.Assert(err, check.IsNil)
+
+	prefix2, err := netip.ParsePrefix(
+		"150.0.10.0/25",
+	)
+	c.Assert(err, check.IsNil)
+
+	hostInfo1 := tailcfg.Hostinfo{
+		RoutableIPs: []netip.Prefix{prefix, prefix2},
+	}
+
+	now := time.Now()
+	machine1 := Machine{
+		ID:             1,
+		MachineKey:     "foo",
+		NodeKey:        "bar",
+		DiscoKey:       "faa",
+		Hostname:       "test_enable_route_machine",
+		NamespaceID:    namespace.ID,
+		RegisterMethod: RegisterMethodAuthKey,
+		AuthKeyID:      uint(pak.ID),
+		HostInfo:       HostInfo(hostInfo1),
+		LastSeen:       &now,
+	}
+	app.db.Save(&machine1)
+
+	err = app.processMachineRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+
+	err = app.EnableRoutes(&machine1, prefix.String())
+	c.Assert(err, check.IsNil)
+
+	err = app.EnableRoutes(&machine1, prefix2.String())
+	c.Assert(err, check.IsNil)
+
+	err = app.handlePrimarySubnetFailover()
+	c.Assert(err, check.IsNil)
+
+	enabledRoutes1, err := app.GetEnabledRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(enabledRoutes1), check.Equals, 2)
+
+	route, err := app.getPrimaryRoute(prefix)
+	c.Assert(err, check.IsNil)
+	c.Assert(route.MachineID, check.Equals, machine1.ID)
+
+	hostInfo2 := tailcfg.Hostinfo{
+		RoutableIPs: []netip.Prefix{prefix2},
+	}
+	machine2 := Machine{
+		ID:             2,
+		MachineKey:     "foo",
+		NodeKey:        "bar",
+		DiscoKey:       "faa",
+		Hostname:       "test_enable_route_machine",
+		NamespaceID:    namespace.ID,
+		RegisterMethod: RegisterMethodAuthKey,
+		AuthKeyID:      uint(pak.ID),
+		HostInfo:       HostInfo(hostInfo2),
+		LastSeen:       &now,
+	}
+	app.db.Save(&machine2)
+
+	err = app.processMachineRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+
+	err = app.EnableRoutes(&machine2, prefix2.String())
+	c.Assert(err, check.IsNil)
+
+	err = app.handlePrimarySubnetFailover()
+	c.Assert(err, check.IsNil)
+
+	enabledRoutes1, err = app.GetEnabledRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(enabledRoutes1), check.Equals, 2)
+
+	enabledRoutes2, err := app.GetEnabledRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(enabledRoutes2), check.Equals, 1)
+
+	routes, err := app.getMachinePrimaryRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 2)
+
+	routes, err = app.getMachinePrimaryRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 0)
+
+	// lets make machine1 lastseen 10 mins ago
+	before := now.Add(-10 * time.Minute)
+	machine1.LastSeen = &before
+	err = app.db.Save(&machine1).Error
+	c.Assert(err, check.IsNil)
+
+	err = app.handlePrimarySubnetFailover()
+	c.Assert(err, check.IsNil)
+
+	routes, err = app.getMachinePrimaryRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 1)
+
+	routes, err = app.getMachinePrimaryRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 1)
+
+	machine2.HostInfo = HostInfo(tailcfg.Hostinfo{
+		RoutableIPs: []netip.Prefix{prefix, prefix2},
+	})
+	err = app.db.Save(&machine2).Error
+	c.Assert(err, check.IsNil)
+
+	err = app.processMachineRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+
+	err = app.EnableRoutes(&machine2, prefix.String())
+	c.Assert(err, check.IsNil)
+
+	err = app.handlePrimarySubnetFailover()
+	c.Assert(err, check.IsNil)
+
+	routes, err = app.getMachinePrimaryRoutes(&machine1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 0)
+
+	routes, err = app.getMachinePrimaryRoutes(&machine2)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(routes), check.Equals, 2)
+}