diff --git a/sharing_nodes_test.go b/sharing_nodes_test.go
new file mode 100644
index 00000000..2c8a7a13
--- /dev/null
+++ b/sharing_nodes_test.go
@@ -0,0 +1,359 @@
+package headscale
+
+import (
+	"gopkg.in/check.v1"
+	"tailscale.com/tailcfg"
+)
+
+func (s *Suite) TestBasicSharedNodesInNamespace(c *check.C) {
+	n1, err := h.CreateNamespace("shared1")
+	c.Assert(err, check.IsNil)
+
+	n2, err := h.CreateNamespace("shared2")
+	c.Assert(err, check.IsNil)
+
+	pak1, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak2, err := h.CreatePreAuthKey(n2.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine(n1.Name, "test_get_shared_nodes_1")
+	c.Assert(err, check.NotNil)
+
+	m1 := Machine{
+		ID:             0,
+		MachineKey:     "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		NodeKey:        "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		DiscoKey:       "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		Name:           "test_get_shared_nodes_1",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.1",
+		AuthKeyID:      uint(pak1.ID),
+	}
+	h.db.Save(&m1)
+
+	_, err = h.GetMachine(n1.Name, m1.Name)
+	c.Assert(err, check.IsNil)
+
+	m2 := Machine{
+		ID:             1,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_2",
+		NamespaceID:    n2.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.2",
+		AuthKeyID:      uint(pak2.ID),
+	}
+	h.db.Save(&m2)
+
+	_, err = h.GetMachine(n2.Name, m2.Name)
+	c.Assert(err, check.IsNil)
+
+	p1s, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1s), check.Equals, 0)
+
+	err = h.ShareNodeInNamespace(&m2, n1)
+	c.Assert(err, check.IsNil)
+
+	p1sAfter, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1sAfter), check.Equals, 1)
+	c.Assert((*p1sAfter)[0].ID, check.Equals, tailcfg.NodeID(m2.ID))
+}
+
+func (s *Suite) TestSameNamespace(c *check.C) {
+	n1, err := h.CreateNamespace("shared1")
+	c.Assert(err, check.IsNil)
+
+	n2, err := h.CreateNamespace("shared2")
+	c.Assert(err, check.IsNil)
+
+	pak1, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak2, err := h.CreatePreAuthKey(n2.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine(n1.Name, "test_get_shared_nodes_1")
+	c.Assert(err, check.NotNil)
+
+	m1 := Machine{
+		ID:             0,
+		MachineKey:     "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		NodeKey:        "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		DiscoKey:       "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		Name:           "test_get_shared_nodes_1",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.1",
+		AuthKeyID:      uint(pak1.ID),
+	}
+	h.db.Save(&m1)
+
+	_, err = h.GetMachine(n1.Name, m1.Name)
+	c.Assert(err, check.IsNil)
+
+	m2 := Machine{
+		ID:             1,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_2",
+		NamespaceID:    n2.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.2",
+		AuthKeyID:      uint(pak2.ID),
+	}
+	h.db.Save(&m2)
+
+	_, err = h.GetMachine(n2.Name, m2.Name)
+	c.Assert(err, check.IsNil)
+
+	p1s, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1s), check.Equals, 0)
+
+	err = h.ShareNodeInNamespace(&m1, n1)
+	c.Assert(err, check.Equals, errorSameNamespace)
+}
+
+func (s *Suite) TestAlreadyShared(c *check.C) {
+	n1, err := h.CreateNamespace("shared1")
+	c.Assert(err, check.IsNil)
+
+	n2, err := h.CreateNamespace("shared2")
+	c.Assert(err, check.IsNil)
+
+	pak1, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak2, err := h.CreatePreAuthKey(n2.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine(n1.Name, "test_get_shared_nodes_1")
+	c.Assert(err, check.NotNil)
+
+	m1 := Machine{
+		ID:             0,
+		MachineKey:     "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		NodeKey:        "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		DiscoKey:       "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		Name:           "test_get_shared_nodes_1",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.1",
+		AuthKeyID:      uint(pak1.ID),
+	}
+	h.db.Save(&m1)
+
+	_, err = h.GetMachine(n1.Name, m1.Name)
+	c.Assert(err, check.IsNil)
+
+	m2 := Machine{
+		ID:             1,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_2",
+		NamespaceID:    n2.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.2",
+		AuthKeyID:      uint(pak2.ID),
+	}
+	h.db.Save(&m2)
+
+	_, err = h.GetMachine(n2.Name, m2.Name)
+	c.Assert(err, check.IsNil)
+
+	p1s, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1s), check.Equals, 0)
+
+	err = h.ShareNodeInNamespace(&m2, n1)
+	c.Assert(err, check.IsNil)
+	err = h.ShareNodeInNamespace(&m2, n1)
+	c.Assert(err, check.Equals, errorNodeAlreadyShared)
+}
+
+func (s *Suite) TestDoNotIncludeRoutesOnShared(c *check.C) {
+	n1, err := h.CreateNamespace("shared1")
+	c.Assert(err, check.IsNil)
+
+	n2, err := h.CreateNamespace("shared2")
+	c.Assert(err, check.IsNil)
+
+	pak1, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak2, err := h.CreatePreAuthKey(n2.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine(n1.Name, "test_get_shared_nodes_1")
+	c.Assert(err, check.NotNil)
+
+	m1 := Machine{
+		ID:             0,
+		MachineKey:     "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		NodeKey:        "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		DiscoKey:       "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		Name:           "test_get_shared_nodes_1",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.1",
+		AuthKeyID:      uint(pak1.ID),
+	}
+	h.db.Save(&m1)
+
+	_, err = h.GetMachine(n1.Name, m1.Name)
+	c.Assert(err, check.IsNil)
+
+	m2 := Machine{
+		ID:             1,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_2",
+		NamespaceID:    n2.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.2",
+		AuthKeyID:      uint(pak2.ID),
+	}
+	h.db.Save(&m2)
+
+	_, err = h.GetMachine(n2.Name, m2.Name)
+	c.Assert(err, check.IsNil)
+
+	p1s, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1s), check.Equals, 0)
+
+	err = h.ShareNodeInNamespace(&m2, n1)
+	c.Assert(err, check.IsNil)
+
+	p1sAfter, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1sAfter), check.Equals, 1)
+	c.Assert(len((*p1sAfter)[0].AllowedIPs), check.Equals, 1)
+}
+
+func (s *Suite) TestComplexSharingAcrossNamespaces(c *check.C) {
+	n1, err := h.CreateNamespace("shared1")
+	c.Assert(err, check.IsNil)
+
+	n2, err := h.CreateNamespace("shared2")
+	c.Assert(err, check.IsNil)
+
+	n3, err := h.CreateNamespace("shared3")
+	c.Assert(err, check.IsNil)
+
+	pak1, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak2, err := h.CreatePreAuthKey(n2.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak3, err := h.CreatePreAuthKey(n3.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	pak4, err := h.CreatePreAuthKey(n1.Name, false, false, nil)
+	c.Assert(err, check.IsNil)
+
+	_, err = h.GetMachine(n1.Name, "test_get_shared_nodes_1")
+	c.Assert(err, check.NotNil)
+
+	m1 := Machine{
+		ID:             0,
+		MachineKey:     "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		NodeKey:        "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		DiscoKey:       "686824e749f3b7f2a5927ee6c1e422aee5292592d9179a271ed7b3e659b44a66",
+		Name:           "test_get_shared_nodes_1",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.1",
+		AuthKeyID:      uint(pak1.ID),
+	}
+	h.db.Save(&m1)
+
+	_, err = h.GetMachine(n1.Name, m1.Name)
+	c.Assert(err, check.IsNil)
+
+	m2 := Machine{
+		ID:             1,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_2",
+		NamespaceID:    n2.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.2",
+		AuthKeyID:      uint(pak2.ID),
+	}
+	h.db.Save(&m2)
+
+	_, err = h.GetMachine(n2.Name, m2.Name)
+	c.Assert(err, check.IsNil)
+
+	m3 := Machine{
+		ID:             2,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_3",
+		NamespaceID:    n3.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.3",
+		AuthKeyID:      uint(pak3.ID),
+	}
+	h.db.Save(&m3)
+
+	_, err = h.GetMachine(n3.Name, m3.Name)
+	c.Assert(err, check.IsNil)
+
+	m4 := Machine{
+		ID:             3,
+		MachineKey:     "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		NodeKey:        "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		DiscoKey:       "dec46ef9dc45c7d2f03bfcd5a640d9e24e3cc68ce3d9da223867c9bc6d5e9863",
+		Name:           "test_get_shared_nodes_4",
+		NamespaceID:    n1.ID,
+		Registered:     true,
+		RegisterMethod: "authKey",
+		IPAddress:      "100.64.0.4",
+		AuthKeyID:      uint(pak4.ID),
+	}
+	h.db.Save(&m4)
+
+	_, err = h.GetMachine(n1.Name, m4.Name)
+	c.Assert(err, check.IsNil)
+
+	p1s, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1s), check.Equals, 1) // nodes 1 and 4
+
+	err = h.ShareNodeInNamespace(&m2, n1)
+	c.Assert(err, check.IsNil)
+
+	p1sAfter, err := h.getPeers(m1)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*p1sAfter), check.Equals, 2) // nodes 1, 2, 4
+
+	pAlone, err := h.getPeers(m3)
+	c.Assert(err, check.IsNil)
+	c.Assert(len(*pAlone), check.Equals, 0) // node 3 is alone
+}