diff --git a/tstest/integration/integration_test.go b/tstest/integration/integration_test.go
index bc296782f..154e0120b 100644
--- a/tstest/integration/integration_test.go
+++ b/tstest/integration/integration_test.go
@@ -10,6 +10,7 @@ import (
 	crand "crypto/rand"
 	"crypto/tls"
 	"encoding/json"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -89,10 +90,7 @@ func TestOneNodeUp_NoAuth(t *testing.T) {
 		t.Error(err)
 	}
 
-	t.Logf("Running up --login-server=%s ...", env.ControlServer.URL)
-	if err := n1.Tailscale("up", "--login-server="+env.ControlServer.URL).Run(); err != nil {
-		t.Fatalf("up: %v", err)
-	}
+	n1.MustUp()
 
 	if d, _ := time.ParseDuration(os.Getenv("TS_POST_UP_SLEEP")); d > 0 {
 		t.Logf("Sleeping for %v to give 'up' time to misbehave (https://github.com/tailscale/tailscale/issues/1840) ...", d)
@@ -116,7 +114,6 @@ func TestOneNodeUp_Auth(t *testing.T) {
 	env.Control.RequireAuth = true
 
 	n1 := newTestNode(t, env)
-
 	d1 := n1.StartDaemon(t)
 	defer d1.Kill()
 
@@ -155,6 +152,50 @@ func TestOneNodeUp_Auth(t *testing.T) {
 
 }
 
+func TestTwoNodes(t *testing.T) {
+	t.Parallel()
+	bins := buildTestBinaries(t)
+
+	env := newTestEnv(t, bins)
+	defer env.Close()
+
+	// Create two nodes:
+	n1 := newTestNode(t, env)
+	d1 := n1.StartDaemon(t)
+	defer d1.Kill()
+
+	n2 := newTestNode(t, env)
+	d2 := n2.StartDaemon(t)
+	defer d2.Kill()
+
+	n1.AwaitListening(t)
+	n2.AwaitListening(t)
+	n1.MustUp()
+	n2.MustUp()
+	n1.AwaitRunning(t)
+	n2.AwaitRunning(t)
+
+	if err := tstest.WaitFor(2*time.Second, func() error {
+		st := n1.MustStatus(t)
+		if len(st.Peer) == 0 {
+			return errors.New("no peers")
+		}
+		if len(st.Peer) > 1 {
+			return fmt.Errorf("got %d peers; want 1", len(st.Peer))
+		}
+		peer := st.Peer[st.Peers()[0]]
+		if peer.ID == st.Self.ID {
+			return errors.New("peer is self")
+		}
+		return nil
+	}); err != nil {
+		t.Error(err)
+	}
+
+	d1.MustCleanShutdown(t)
+	d2.MustCleanShutdown(t)
+}
+
 // testBinaries are the paths to a tailscaled and tailscale binary.
 // These can be shared by multiple nodes.
 type testBinaries struct {
@@ -298,6 +339,14 @@ func (n *testNode) StartDaemon(t testing.TB) *Daemon {
 	}
 }
 
+func (n *testNode) MustUp() {
+	t := n.env.t
+	t.Logf("Running up --login-server=%s ...", n.env.ControlServer.URL)
+	if err := n.Tailscale("up", "--login-server="+n.env.ControlServer.URL).Run(); err != nil {
+		t.Fatalf("up: %v", err)
+	}
+}
+
 // AwaitListening waits for the tailscaled to be serving local clients
 // over its localhost IPC mechanism. (Unix socket, etc)
 func (n *testNode) AwaitListening(t testing.TB) {
diff --git a/tstest/integration/testcontrol/testcontrol.go b/tstest/integration/testcontrol/testcontrol.go
index cd1051c58..1771bf65a 100644
--- a/tstest/integration/testcontrol/testcontrol.go
+++ b/tstest/integration/testcontrol/testcontrol.go
@@ -18,6 +18,7 @@ import (
 	"math/rand"
 	"net/http"
 	"net/url"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -167,6 +168,18 @@ func (s *Server) Node(nodeKey tailcfg.NodeKey) *tailcfg.Node {
 	return s.nodes[nodeKey].Clone()
 }
 
+func (s *Server) AllNodes() (nodes []*tailcfg.Node) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for _, n := range s.nodes {
+		nodes = append(nodes, n.Clone())
+	}
+	sort.Slice(nodes, func(i, j int) bool {
+		return nodes[i].StableID < nodes[j].StableID
+	})
+	return nodes
+}
+
 func (s *Server) getUser(nodeKey tailcfg.NodeKey) (*tailcfg.User, *tailcfg.Login) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -366,6 +379,21 @@ func sendUpdate(dst chan<- updateType, updateType updateType) {
 	}
 }
 
+func (s *Server) UpdateNode(n *tailcfg.Node) (peersToUpdate []tailcfg.NodeID) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if n.Key.IsZero() {
+		panic("zero nodekey")
+	}
+	s.nodes[n.Key] = n.Clone()
+	for _, n2 := range s.nodes {
+		if n.ID != n2.ID {
+			peersToUpdate = append(peersToUpdate, n2.ID)
+		}
+	}
+	return peersToUpdate
+}
+
 func (s *Server) serveMap(w http.ResponseWriter, r *http.Request, mkey tailcfg.MachineKey) {
 	ctx := r.Context()
 
@@ -391,10 +419,8 @@ func (s *Server) serveMap(w http.ResponseWriter, r *http.Request, mkey tailcfg.M
 	if !req.ReadOnly {
 		endpoints := filterInvalidIPv6Endpoints(req.Endpoints)
 		node.Endpoints = endpoints
-		// TODO: more
-		// TODO: register node,
-		//s.UpdateEndpoint(mkey, req.NodeKey,
-		// XXX
+		node.DiscoKey = req.DiscoKey
+		peersToUpdate = s.UpdateNode(node)
 	}
 
 	nodeID := node.ID
@@ -501,6 +527,12 @@ func (s *Server) MapResponse(req *tailcfg.MapRequest) (res *tailcfg.MapResponse,
 		CollectServices: "true",
 		PacketFilter:    tailcfg.FilterAllowAll,
 	}
+	for _, p := range s.AllNodes() {
+		if p.StableID != node.StableID {
+			res.Peers = append(res.Peers, p)
+		}
+	}
+
 	res.Node.Addresses = []netaddr.IPPrefix{
 		netaddr.MustParseIPPrefix(fmt.Sprintf("100.64.%d.%d/32", uint8(node.ID>>8), uint8(node.ID))),
 	}