diff --git a/cmd/derper/depaware.txt b/cmd/derper/depaware.txt
index 7e82305d1..b40ca360a 100644
--- a/cmd/derper/depaware.txt
+++ b/cmd/derper/depaware.txt
@@ -86,7 +86,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
      💣 tailscale.com/net/interfaces                                 from tailscale.com/net/netns+
         tailscale.com/net/netaddr                                    from tailscale.com/ipn+
         tailscale.com/net/netknob                                    from tailscale.com/net/netns
-        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats
+        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats+
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp
         tailscale.com/net/netutil                                    from tailscale.com/client/tailscale
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter
diff --git a/cmd/tailscale/cli/netcheck.go b/cmd/tailscale/cli/netcheck.go
index 0c2f7acd1..bac5a0a48 100644
--- a/cmd/tailscale/cli/netcheck.go
+++ b/cmd/tailscale/cli/netcheck.go
@@ -19,6 +19,7 @@
 	"tailscale.com/envknob"
 	"tailscale.com/ipn"
 	"tailscale.com/net/netcheck"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/portmapper"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
@@ -45,9 +46,14 @@
 }
 
 func runNetcheck(ctx context.Context, args []string) error {
+	logf := logger.WithPrefix(log.Printf, "portmap: ")
+	netMon, err := netmon.New(logf)
+	if err != nil {
+		return err
+	}
 	c := &netcheck.Client{
 		UDPBindAddr: envknob.String("TS_DEBUG_NETCHECK_UDP_BIND"),
-		PortMapper:  portmapper.NewClient(logger.WithPrefix(log.Printf, "portmap: "), nil, nil),
+		PortMapper:  portmapper.NewClient(logf, netMon, nil, nil),
 		UseDNSCache: false, // always resolve, don't cache
 	}
 	if netcheckArgs.verbose {
diff --git a/cmd/tailscale/depaware.txt b/cmd/tailscale/depaware.txt
index b146ec567..5b644992e 100644
--- a/cmd/tailscale/depaware.txt
+++ b/cmd/tailscale/depaware.txt
@@ -74,7 +74,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/net/netcheck                                   from tailscale.com/cmd/tailscale/cli
         tailscale.com/net/neterror                                   from tailscale.com/net/netcheck+
         tailscale.com/net/netknob                                    from tailscale.com/net/netns
-        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats
+        tailscale.com/net/netmon                                     from tailscale.com/net/sockstats+
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp+
         tailscale.com/net/netutil                                    from tailscale.com/client/tailscale+
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter+
diff --git a/cmd/tailscaled/debug.go b/cmd/tailscaled/debug.go
index 8c1ad88b1..b6a95ba49 100644
--- a/cmd/tailscaled/debug.go
+++ b/cmd/tailscaled/debug.go
@@ -193,8 +193,8 @@ func checkDerp(ctx context.Context, derpRegion string) (err error) {
 	priv1 := key.NewNode()
 	priv2 := key.NewNode()
 
-	c1 := derphttp.NewRegionClient(priv1, log.Printf, getRegion)
-	c2 := derphttp.NewRegionClient(priv2, log.Printf, getRegion)
+	c1 := derphttp.NewRegionClient(priv1, log.Printf, nil, getRegion)
+	c2 := derphttp.NewRegionClient(priv2, log.Printf, nil, getRegion)
 	defer func() {
 		if err != nil {
 			c1.Close()
diff --git a/cmd/tailscaled/tailscaled.go b/cmd/tailscaled/tailscaled.go
index 3bae560a2..d2c28de99 100644
--- a/cmd/tailscaled/tailscaled.go
+++ b/cmd/tailscaled/tailscaled.go
@@ -329,7 +329,15 @@ func ipnServerOpts() (o serverOptions) {
 var debugMux *http.ServeMux
 
 func run() error {
-	pol := logpolicy.New(logtail.CollectionNode)
+	var logf logger.Logf = log.Printf
+	netMon, err := netmon.New(func(format string, args ...any) {
+		logf(format, args...)
+	})
+	if err != nil {
+		return fmt.Errorf("netmon.New: %w", err)
+	}
+
+	pol := logpolicy.New(logtail.CollectionNode, netMon)
 	pol.SetVerbosityLevel(args.verbose)
 	logPol = pol
 	defer func() {
@@ -353,7 +361,6 @@ func run() error {
 		return nil
 	}
 
-	var logf logger.Logf = log.Printf
 	if envknob.Bool("TS_DEBUG_MEMORY") {
 		logf = logger.RusagePrefixLog(logf)
 	}
@@ -379,10 +386,10 @@ func run() error {
 		debugMux = newDebugMux()
 	}
 
-	return startIPNServer(context.Background(), logf, pol.PublicID)
+	return startIPNServer(context.Background(), logf, pol.PublicID, netMon)
 }
 
-func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID) error {
+func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID, netMon *netmon.Monitor) error {
 	ln, err := safesocket.Listen(args.socketpath)
 	if err != nil {
 		return fmt.Errorf("safesocket.Listen: %v", err)
@@ -408,7 +415,7 @@ func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID)
 		}
 	}()
 
-	srv := ipnserver.New(logf, logID)
+	srv := ipnserver.New(logf, logID, netMon)
 	if debugMux != nil {
 		debugMux.HandleFunc("/debug/ipn", srv.ServeHTMLStatus)
 	}
@@ -426,7 +433,7 @@ func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID)
 				return
 			}
 		}
-		lb, err := getLocalBackend(ctx, logf, logID)
+		lb, err := getLocalBackend(ctx, logf, logID, netMon)
 		if err == nil {
 			logf("got LocalBackend in %v", time.Since(t0).Round(time.Millisecond))
 			srv.SetLocalBackend(lb)
@@ -450,11 +457,7 @@ func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID)
 	return nil
 }
 
-func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID) (_ *ipnlocal.LocalBackend, retErr error) {
-	netMon, err := netmon.New(logf)
-	if err != nil {
-		return nil, fmt.Errorf("netmon.New: %w", err)
-	}
+func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID, netMon *netmon.Monitor) (_ *ipnlocal.LocalBackend, retErr error) {
 	if logPol != nil {
 		logPol.Logtail.SetNetMon(netMon)
 	}
diff --git a/cmd/tailscaled/tailscaled_windows.go b/cmd/tailscaled/tailscaled_windows.go
index a654dadf4..077d3f99f 100644
--- a/cmd/tailscaled/tailscaled_windows.go
+++ b/cmd/tailscaled/tailscaled_windows.go
@@ -45,6 +45,7 @@
 	"tailscale.com/logpolicy"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/net/dns"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tstun"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
@@ -291,8 +292,13 @@ func beWindowsSubprocess() bool {
 		}
 	}()
 
+	netMon, err := netmon.New(log.Printf)
+	if err != nil {
+		log.Printf("Could not create netMon: %v", err)
+		netMon = nil
+	}
 	publicLogID, _ := logid.ParsePublicID(logID)
-	err := startIPNServer(ctx, log.Printf, publicLogID)
+	err = startIPNServer(ctx, log.Printf, publicLogID, netMon)
 	if err != nil {
 		log.Fatalf("ipnserver: %v", err)
 	}
diff --git a/cmd/tsconnect/wasm/wasm_js.go b/cmd/tsconnect/wasm/wasm_js.go
index f94b850a2..a1b0fd95e 100644
--- a/cmd/tsconnect/wasm/wasm_js.go
+++ b/cmd/tsconnect/wasm/wasm_js.go
@@ -123,7 +123,7 @@ func newIPN(jsConfig js.Value) map[string]any {
 	}
 
 	logid := lpc.PublicID
-	srv := ipnserver.New(logf, logid)
+	srv := ipnserver.New(logf, logid, nil /* no netMon */)
 	lb, err := ipnlocal.NewLocalBackend(logf, logid, store, dialer, eng, controlclient.LoginEphemeral)
 	if err != nil {
 		log.Fatalf("ipnlocal.NewLocalBackend: %v", err)
diff --git a/control/controlclient/direct.go b/control/controlclient/direct.go
index 85bd7f07b..cf6fd9987 100644
--- a/control/controlclient/direct.go
+++ b/control/controlclient/direct.go
@@ -211,8 +211,9 @@ func NewDirect(opts Options) (*Direct, error) {
 		dnsCache := &dnscache.Resolver{
 			Forward:          dnscache.Get().Forward, // use default cache's forwarder
 			UseLastGood:      true,
-			LookupIPFallback: dnsfallback.Lookup(opts.Logf),
+			LookupIPFallback: dnsfallback.MakeLookupFunc(opts.Logf, opts.NetMon),
 			Logf:             opts.Logf,
+			NetMon:           opts.NetMon,
 		}
 		tr := http.DefaultTransport.(*http.Transport).Clone()
 		tr.Proxy = tshttpproxy.ProxyFromEnvironment
@@ -1508,7 +1509,7 @@ func (c *Direct) getNoiseClient() (*NoiseClient, error) {
 			return nil, err
 		}
 		c.logf("creating new noise client")
-		nc, err := NewNoiseClient(k, serverNoiseKey, c.serverURL, c.dialer, dp)
+		nc, err := NewNoiseClient(k, serverNoiseKey, c.serverURL, c.dialer, c.logf, c.netMon, dp)
 		if err != nil {
 			return nil, err
 		}
diff --git a/control/controlclient/noise.go b/control/controlclient/noise.go
index 826b0c249..61c472a35 100644
--- a/control/controlclient/noise.go
+++ b/control/controlclient/noise.go
@@ -19,9 +19,11 @@
 	"golang.org/x/net/http2"
 	"tailscale.com/control/controlbase"
 	"tailscale.com/control/controlhttp"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
+	"tailscale.com/types/logger"
 	"tailscale.com/util/mak"
 	"tailscale.com/util/multierr"
 	"tailscale.com/util/singleflight"
@@ -167,6 +169,9 @@ type NoiseClient struct {
 	// be nil.
 	dialPlan func() *tailcfg.ControlDialPlan
 
+	logf   logger.Logf
+	netMon *netmon.Monitor
+
 	// mu only protects the following variables.
 	mu       sync.Mutex
 	last     *noiseConn // or nil
@@ -177,8 +182,9 @@ type NoiseClient struct {
 // NewNoiseClient returns a new noiseClient for the provided server and machine key.
 // serverURL is of the form https://<host>:<port> (no trailing slash).
 //
+// netMon may be nil, if non-nil it's used to do faster interface lookups.
 // dialPlan may be nil
-func NewNoiseClient(privKey key.MachinePrivate, serverPubKey key.MachinePublic, serverURL string, dialer *tsdial.Dialer, dialPlan func() *tailcfg.ControlDialPlan) (*NoiseClient, error) {
+func NewNoiseClient(privKey key.MachinePrivate, serverPubKey key.MachinePublic, serverURL string, dialer *tsdial.Dialer, logf logger.Logf, netMon *netmon.Monitor, dialPlan func() *tailcfg.ControlDialPlan) (*NoiseClient, error) {
 	u, err := url.Parse(serverURL)
 	if err != nil {
 		return nil, err
@@ -207,6 +213,8 @@ func NewNoiseClient(privKey key.MachinePrivate, serverPubKey key.MachinePublic,
 		httpsPort:    httpsPort,
 		dialer:       dialer,
 		dialPlan:     dialPlan,
+		logf:         logf,
+		netMon:       netMon,
 	}
 
 	// Create the HTTP/2 Transport using a net/http.Transport
@@ -366,6 +374,8 @@ func (nc *NoiseClient) dial() (*noiseConn, error) {
 		ProtocolVersion: uint16(tailcfg.CurrentCapabilityVersion),
 		Dialer:          nc.dialer.SystemDial,
 		DialPlan:        dialPlan,
+		Logf:            nc.logf,
+		NetMon:          nc.netMon,
 	}).Dial(ctx)
 	if err != nil {
 		return nil, err
diff --git a/control/controlclient/noise_test.go b/control/controlclient/noise_test.go
index 049e260fe..11e35f0af 100644
--- a/control/controlclient/noise_test.go
+++ b/control/controlclient/noise_test.go
@@ -74,7 +74,7 @@ func (tt noiseClientTest) run(t *testing.T) {
 	defer hs.Close()
 
 	dialer := new(tsdial.Dialer)
-	nc, err := NewNoiseClient(clientPrivate, serverPrivate.Public(), hs.URL, dialer, nil)
+	nc, err := NewNoiseClient(clientPrivate, serverPrivate.Public(), hs.URL, dialer, nil, nil, nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/control/controlhttp/client.go b/control/controlhttp/client.go
index 02b5a7821..d04aac518 100644
--- a/control/controlhttp/client.go
+++ b/control/controlhttp/client.go
@@ -389,13 +389,15 @@ func (a *Dialer) tryURLUpgrade(ctx context.Context, u *url.URL, addr netip.Addr,
 			SingleHostStaticResult: []netip.Addr{addr},
 			SingleHost:             u.Hostname(),
 			Logf:                   a.Logf, // not a.logf method; we want to propagate nil-ness
+			NetMon:                 a.NetMon,
 		}
 	} else {
 		dns = &dnscache.Resolver{
 			Forward:          dnscache.Get().Forward,
-			LookupIPFallback: dnsfallback.Lookup(a.logf),
+			LookupIPFallback: dnsfallback.MakeLookupFunc(a.logf, a.NetMon),
 			UseLastGood:      true,
 			Logf:             a.Logf, // not a.logf method; we want to propagate nil-ness
+			NetMon:           a.NetMon,
 		}
 	}
 
diff --git a/control/controlhttp/constants.go b/control/controlhttp/constants.go
index 045eeba7f..a58ee5374 100644
--- a/control/controlhttp/constants.go
+++ b/control/controlhttp/constants.go
@@ -9,6 +9,7 @@
 	"time"
 
 	"tailscale.com/net/dnscache"
+	"tailscale.com/net/netmon"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
@@ -70,6 +71,8 @@ type Dialer struct {
 	// dropped.
 	Logf logger.Logf
 
+	NetMon *netmon.Monitor
+
 	// DialPlan, if set, contains instructions from the control server on
 	// how to connect to it. If present, we will try the methods in this
 	// plan before falling back to DNS.
diff --git a/derp/derphttp/derphttp_client.go b/derp/derphttp/derphttp_client.go
index 349838dfa..2ea86b686 100644
--- a/derp/derphttp/derphttp_client.go
+++ b/derp/derphttp/derphttp_client.go
@@ -31,6 +31,7 @@
 	"tailscale.com/derp"
 	"tailscale.com/envknob"
 	"tailscale.com/net/dnscache"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tlsdial"
@@ -55,6 +56,7 @@ type Client struct {
 
 	privateKey key.NodePrivate
 	logf       logger.Logf
+	netMon     *netmon.Monitor // optional; nil means interfaces will be looked up on-demand
 	dialer     func(ctx context.Context, network, addr string) (net.Conn, error)
 
 	// Either url or getRegion is non-nil:
@@ -88,11 +90,13 @@ func (c *Client) String() string {
 
 // NewRegionClient returns a new DERP-over-HTTP client. It connects lazily.
 // To trigger a connection, use Connect.
-func NewRegionClient(privateKey key.NodePrivate, logf logger.Logf, getRegion func() *tailcfg.DERPRegion) *Client {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func NewRegionClient(privateKey key.NodePrivate, logf logger.Logf, netMon *netmon.Monitor, getRegion func() *tailcfg.DERPRegion) *Client {
 	ctx, cancel := context.WithCancel(context.Background())
 	c := &Client{
 		privateKey: privateKey,
 		logf:       logf,
+		netMon:     netMon,
 		getRegion:  getRegion,
 		ctx:        ctx,
 		cancelCtx:  cancel,
@@ -492,7 +496,7 @@ func (c *Client) dialURL(ctx context.Context) (net.Conn, error) {
 		return c.dialer(ctx, "tcp", net.JoinHostPort(host, urlPort(c.url)))
 	}
 	hostOrIP := host
-	dialer := netns.NewDialer(c.logf)
+	dialer := netns.NewDialer(c.logf, c.netMon)
 
 	if c.DNSCache != nil {
 		ip, _, _, err := c.DNSCache.LookupIP(ctx, host)
@@ -587,7 +591,7 @@ func (c *Client) DialRegionTLS(ctx context.Context, reg *tailcfg.DERPRegion) (tl
 }
 
 func (c *Client) dialContext(ctx context.Context, proto, addr string) (net.Conn, error) {
-	return netns.NewDialer(c.logf).DialContext(ctx, proto, addr)
+	return netns.NewDialer(c.logf, c.netMon).DialContext(ctx, proto, addr)
 }
 
 // shouldDialProto reports whether an explicitly provided IPv4 or IPv6
diff --git a/ipn/ipnlocal/local.go b/ipn/ipnlocal/local.go
index 532e68d19..d1aaf6b89 100644
--- a/ipn/ipnlocal/local.go
+++ b/ipn/ipnlocal/local.go
@@ -313,7 +313,7 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, store ipn.StateStor
 		loginFlags:     loginFlags,
 	}
 
-	b.sockstatLogger, err = sockstatlog.NewLogger(logpolicy.LogsDir(logf), logf, logID)
+	b.sockstatLogger, err = sockstatlog.NewLogger(logpolicy.LogsDir(logf), logf, logID, e.GetNetMon())
 	if err != nil {
 		log.Printf("error setting up sockstat logger: %v", err)
 	}
diff --git a/ipn/ipnserver/proxyconnect.go b/ipn/ipnserver/proxyconnect.go
index 8f330add1..5ac7e89db 100644
--- a/ipn/ipnserver/proxyconnect.go
+++ b/ipn/ipnserver/proxyconnect.go
@@ -37,7 +37,8 @@ func (s *Server) handleProxyConnectConn(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	back, err := logpolicy.DialContext(ctx, "tcp", hostPort)
+	dialContext := logpolicy.MakeDialFunc(s.netMon)
+	back, err := dialContext(ctx, "tcp", hostPort)
 	if err != nil {
 		s.logf("error CONNECT dialing %v: %v", hostPort, err)
 		http.Error(w, "Connect failure", http.StatusBadGateway)
diff --git a/ipn/ipnserver/server.go b/ipn/ipnserver/server.go
index 0123d9e9e..3abfa9364 100644
--- a/ipn/ipnserver/server.go
+++ b/ipn/ipnserver/server.go
@@ -24,6 +24,7 @@
 	"tailscale.com/ipn/ipnauth"
 	"tailscale.com/ipn/ipnlocal"
 	"tailscale.com/ipn/localapi"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
 	"tailscale.com/util/mak"
@@ -36,6 +37,7 @@
 type Server struct {
 	lb           atomic.Pointer[ipnlocal.LocalBackend]
 	logf         logger.Logf
+	netMon       *netmon.Monitor // optional; nil means interfaces will be looked up on-demand
 	backendLogID logid.PublicID
 	// resetOnZero is whether to call bs.Reset on transition from
 	// 1->0 active HTTP requests. That is, this is whether the backend is
@@ -197,7 +199,7 @@ func (s *Server) serveHTTP(w http.ResponseWriter, r *http.Request) {
 	defer onDone()
 
 	if strings.HasPrefix(r.URL.Path, "/localapi/") {
-		lah := localapi.NewHandler(lb, s.logf, s.backendLogID)
+		lah := localapi.NewHandler(lb, s.logf, s.netMon, s.backendLogID)
 		lah.PermitRead, lah.PermitWrite = s.localAPIPermissions(ci)
 		lah.PermitCert = s.connCanFetchCerts(ci)
 		lah.ServeHTTP(w, r)
@@ -408,15 +410,18 @@ func (s *Server) addActiveHTTPRequest(req *http.Request, ci *ipnauth.ConnIdentit
 }
 
 // New returns a new Server.
+// The netMon parameter is optional; if non-nil it's used to do faster interface
+// lookups.
 //
 // To start it, use the Server.Run method.
 //
 // At some point, either before or after Run, the Server's SetLocalBackend
 // method must also be called before Server can do anything useful.
-func New(logf logger.Logf, logID logid.PublicID) *Server {
+func New(logf logger.Logf, logID logid.PublicID, netMon *netmon.Monitor) *Server {
 	return &Server{
 		backendLogID: logID,
 		logf:         logf,
+		netMon:       netMon,
 		resetOnZero:  envknob.GOOS() == "windows",
 	}
 }
diff --git a/ipn/localapi/debugderp.go b/ipn/localapi/debugderp.go
index f7ae88787..af2527ee8 100644
--- a/ipn/localapi/debugderp.go
+++ b/ipn/localapi/debugderp.go
@@ -140,7 +140,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 	}
 
 	checkSTUN4 := func(derpNode *tailcfg.DERPNode) {
-		u4, err := nettype.MakePacketListenerWithNetIP(netns.Listener(h.logf)).ListenPacket(ctx, "udp4", ":0")
+		u4, err := nettype.MakePacketListenerWithNetIP(netns.Listener(h.logf, h.netMon)).ListenPacket(ctx, "udp4", ":0")
 		if err != nil {
 			st.Errors = append(st.Errors, fmt.Sprintf("Error creating IPv4 STUN listener: %v", err))
 			return
@@ -249,7 +249,7 @@ func (h *Handler) serveDebugDERPRegion(w http.ResponseWriter, r *http.Request) {
 		serverPubKeys := make(map[key.NodePublic]bool)
 		for i := 0; i < 5; i++ {
 			func() {
-				rc := derphttp.NewRegionClient(fakePrivKey, h.logf, func() *tailcfg.DERPRegion {
+				rc := derphttp.NewRegionClient(fakePrivKey, h.logf, h.netMon, func() *tailcfg.DERPRegion {
 					return &tailcfg.DERPRegion{
 						RegionID:   reg.RegionID,
 						RegionCode: reg.RegionCode,
diff --git a/ipn/localapi/localapi.go b/ipn/localapi/localapi.go
index be15cbe08..28371a45d 100644
--- a/ipn/localapi/localapi.go
+++ b/ipn/localapi/localapi.go
@@ -125,8 +125,10 @@ func randHex(n int) string {
 	metrics   = map[string]*clientmetric.Metric{}
 )
 
-func NewHandler(b *ipnlocal.LocalBackend, logf logger.Logf, logID logid.PublicID) *Handler {
-	return &Handler{b: b, logf: logf, backendLogID: logID}
+// NewHandler creates a new LocalAPI HTTP handler. All parameters except netMon
+// are required (if non-nil it's used to do faster interface lookups).
+func NewHandler(b *ipnlocal.LocalBackend, logf logger.Logf, netMon *netmon.Monitor, logID logid.PublicID) *Handler {
+	return &Handler{b: b, logf: logf, netMon: netMon, backendLogID: logID}
 }
 
 type Handler struct {
@@ -150,6 +152,7 @@ type Handler struct {
 
 	b            *ipnlocal.LocalBackend
 	logf         logger.Logf
+	netMon       *netmon.Monitor // optional; nil means interfaces will be looked up on-demand
 	backendLogID logid.PublicID
 }
 
@@ -679,7 +682,7 @@ func (h *Handler) serveDebugPortmap(w http.ResponseWriter, r *http.Request) {
 	done := make(chan bool, 1)
 
 	var c *portmapper.Client
-	c = portmapper.NewClient(logger.WithPrefix(logf, "portmapper: "), debugKnobs, func() {
+	c = portmapper.NewClient(logger.WithPrefix(logf, "portmapper: "), h.netMon, debugKnobs, func() {
 		logf("portmapping changed.")
 		logf("have mapping: %v", c.HaveMapping())
 
diff --git a/log/sockstatlog/logger.go b/log/sockstatlog/logger.go
index 683342a08..4f522f17d 100644
--- a/log/sockstatlog/logger.go
+++ b/log/sockstatlog/logger.go
@@ -20,6 +20,7 @@
 	"tailscale.com/logpolicy"
 	"tailscale.com/logtail"
 	"tailscale.com/logtail/filch"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/smallzstd"
 	"tailscale.com/types/logger"
@@ -92,7 +93,8 @@ func SockstatLogID(logID logid.PublicID) logid.PrivateID {
 // On platforms that do not support sockstat logging, a nil Logger will be returned.
 // The returned Logger is not yet enabled, and must be shut down with Shutdown when it is no longer needed.
 // Logs will be uploaded to the log server using a new log ID derived from the provided backend logID.
-func NewLogger(logdir string, logf logger.Logf, logID logid.PublicID) (*Logger, error) {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func NewLogger(logdir string, logf logger.Logf, logID logid.PublicID, netMon *netmon.Monitor) (*Logger, error) {
 	if !sockstats.IsAvailable {
 		return nil, nil
 	}
@@ -112,7 +114,7 @@ func NewLogger(logdir string, logf logger.Logf, logID logid.PublicID) (*Logger,
 	logger := &Logger{
 		logf:  logf,
 		filch: filch,
-		tr:    logpolicy.NewLogtailTransport(logtail.DefaultHost),
+		tr:    logpolicy.NewLogtailTransport(logtail.DefaultHost, netMon),
 	}
 	logger.logger = logtail.NewLogger(logtail.Config{
 		BaseURL:    logpolicy.LogURL(),
diff --git a/log/sockstatlog/logger_test.go b/log/sockstatlog/logger_test.go
index e64a5de8b..1e2d67d97 100644
--- a/log/sockstatlog/logger_test.go
+++ b/log/sockstatlog/logger_test.go
@@ -23,7 +23,7 @@ func TestResourceCleanup(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	lg, err := NewLogger(td, logger.Discard, id.Public())
+	lg, err := NewLogger(td, logger.Discard, id.Public(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/logpolicy/logpolicy.go b/logpolicy/logpolicy.go
index 84da5f31a..7becc934f 100644
--- a/logpolicy/logpolicy.go
+++ b/logpolicy/logpolicy.go
@@ -37,6 +37,7 @@
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/dnsfallback"
 	"tailscale.com/net/netknob"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tshttpproxy"
@@ -450,14 +451,15 @@ func tryFixLogStateLocation(dir, cmdname string) {
 
 // New returns a new log policy (a logger and its instance ID) for a
 // given collection name.
-func New(collection string) *Policy {
-	return NewWithConfigPath(collection, "", "")
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func New(collection string, netMon *netmon.Monitor) *Policy {
+	return NewWithConfigPath(collection, "", "", netMon)
 }
 
 // NewWithConfigPath is identical to New,
 // but uses the specified directory and command name.
 // If either is empty, it derives them automatically.
-func NewWithConfigPath(collection, dir, cmdName string) *Policy {
+func NewWithConfigPath(collection, dir, cmdName string, netMon *netmon.Monitor) *Policy {
 	var lflags int
 	if term.IsTerminal(2) || runtime.GOOS == "windows" {
 		lflags = 0
@@ -554,7 +556,7 @@ func NewWithConfigPath(collection, dir, cmdName string) *Policy {
 			}
 			return w
 		},
-		HTTPC: &http.Client{Transport: NewLogtailTransport(logtail.DefaultHost)},
+		HTTPC: &http.Client{Transport: NewLogtailTransport(logtail.DefaultHost, netMon)},
 	}
 	if collection == logtail.CollectionNode {
 		conf.MetricsDelta = clientmetric.EncodeLogTailMetricsDelta
@@ -569,7 +571,7 @@ func NewWithConfigPath(collection, dir, cmdName string) *Policy {
 		log.Println("You have enabled a non-default log target. Doing without being told to by Tailscale staff or your network administrator will make getting support difficult.")
 		conf.BaseURL = val
 		u, _ := url.Parse(val)
-		conf.HTTPC = &http.Client{Transport: NewLogtailTransport(u.Host)}
+		conf.HTTPC = &http.Client{Transport: NewLogtailTransport(u.Host, netMon)}
 	}
 
 	filchOptions := filch.Options{
@@ -670,13 +672,22 @@ func (p *Policy) Shutdown(ctx context.Context) error {
 	return nil
 }
 
-// DialContext is a net.Dialer.DialContext specialized for use by logtail.
+// MakeDialFunc creates a net.Dialer.DialContext function specialized for use
+// by logtail.
 // It does the following:
 //   - If DNS lookup fails, consults the bootstrap DNS list of Tailscale hostnames.
 //   - If TLS connection fails, try again using LetsEncrypt's built-in root certificate,
 //     for the benefit of older OS platforms which might not include it.
-func DialContext(ctx context.Context, netw, addr string) (net.Conn, error) {
-	nd := netns.FromDialer(log.Printf, &net.Dialer{
+//
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func MakeDialFunc(netMon *netmon.Monitor) func(ctx context.Context, netw, addr string) (net.Conn, error) {
+	return func(ctx context.Context, netw, addr string) (net.Conn, error) {
+		return dialContext(ctx, netw, addr, netMon)
+	}
+}
+
+func dialContext(ctx context.Context, netw, addr string, netMon *netmon.Monitor) (net.Conn, error) {
+	nd := netns.FromDialer(log.Printf, netMon, &net.Dialer{
 		Timeout:   30 * time.Second,
 		KeepAlive: netknob.PlatformTCPKeepAlive(),
 	})
@@ -711,7 +722,8 @@ func DialContext(ctx context.Context, netw, addr string) (net.Conn, error) {
 	dnsCache := &dnscache.Resolver{
 		Forward:          dnscache.Get().Forward, // use default cache's forwarder
 		UseLastGood:      true,
-		LookupIPFallback: dnsfallback.Lookup(log.Printf),
+		LookupIPFallback: dnsfallback.MakeLookupFunc(log.Printf, netMon),
+		NetMon:           netMon,
 	}
 	dialer := dnscache.Dialer(nd.DialContext, dnsCache)
 	c, err = dialer(ctx, netw, addr)
@@ -723,7 +735,8 @@ func DialContext(ctx context.Context, netw, addr string) (net.Conn, error) {
 
 // NewLogtailTransport returns an HTTP Transport particularly suited to uploading
 // logs to the given host name. See DialContext for details on how it works.
-func NewLogtailTransport(host string) http.RoundTripper {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func NewLogtailTransport(host string, netMon *netmon.Monitor) http.RoundTripper {
 	if inTest() {
 		return noopPretendSuccessTransport{}
 	}
@@ -739,7 +752,7 @@ func NewLogtailTransport(host string) http.RoundTripper {
 	tr.DisableCompression = true
 
 	// Log whenever we dial:
-	tr.DialContext = DialContext
+	tr.DialContext = MakeDialFunc(netMon)
 
 	// We're contacting exactly 1 hostname, so the default's 100
 	// max idle conns is very high for our needs. Even 2 is
diff --git a/net/dns/manager.go b/net/dns/manager.go
index e909cbe5d..d1aa73ca6 100644
--- a/net/dns/manager.go
+++ b/net/dns/manager.go
@@ -64,6 +64,7 @@ type Manager struct {
 }
 
 // NewManagers created a new manager from the given config.
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
 func NewManager(logf logger.Logf, oscfg OSConfigurator, netMon *netmon.Monitor, dialer *tsdial.Dialer, linkSel resolver.ForwardLinkSelector) *Manager {
 	if dialer == nil {
 		panic("nil Dialer")
diff --git a/net/dns/resolver/forwarder.go b/net/dns/resolver/forwarder.go
index 3373ffcf1..85670e1d6 100644
--- a/net/dns/resolver/forwarder.go
+++ b/net/dns/resolver/forwarder.go
@@ -380,11 +380,12 @@ func (f *forwarder) getKnownDoHClientForProvider(urlBase string) (c *http.Client
 	if err != nil {
 		return nil, false
 	}
-	nsDialer := netns.NewDialer(f.logf)
+	nsDialer := netns.NewDialer(f.logf, f.netMon)
 	dialer := dnscache.Dialer(nsDialer.DialContext, &dnscache.Resolver{
 		SingleHost:             dohURL.Hostname(),
 		SingleHostStaticResult: allIPs,
 		Logf:                   f.logf,
+		NetMon:                 f.netMon,
 	})
 	c = &http.Client{
 		Transport: &http.Transport{
diff --git a/net/dns/resolver/macios_ext.go b/net/dns/resolver/macios_ext.go
index 895b8714f..e3f979c19 100644
--- a/net/dns/resolver/macios_ext.go
+++ b/net/dns/resolver/macios_ext.go
@@ -17,8 +17,8 @@ func init() {
 	initListenConfig = initListenConfigNetworkExtension
 }
 
-func initListenConfigNetworkExtension(nc *net.ListenConfig, mon *netmon.Monitor, tunName string) error {
-	nif, ok := mon.InterfaceState().Interface[tunName]
+func initListenConfigNetworkExtension(nc *net.ListenConfig, netMon *netmon.Monitor, tunName string) error {
+	nif, ok := netMon.InterfaceState().Interface[tunName]
 	if !ok {
 		return errors.New("utun not found")
 	}
diff --git a/net/dns/resolver/tsdns_test.go b/net/dns/resolver/tsdns_test.go
index ad3d36c99..8db97f49a 100644
--- a/net/dns/resolver/tsdns_test.go
+++ b/net/dns/resolver/tsdns_test.go
@@ -997,7 +997,7 @@ func TestMarshalResponseFormatError(t *testing.T) {
 
 func TestForwardLinkSelection(t *testing.T) {
 	configCall := make(chan string, 1)
-	tstest.Replace(t, &initListenConfig, func(nc *net.ListenConfig, mon *netmon.Monitor, tunName string) error {
+	tstest.Replace(t, &initListenConfig, func(nc *net.ListenConfig, netMon *netmon.Monitor, tunName string) error {
 		select {
 		case configCall <- tunName:
 			return nil
diff --git a/net/dnscache/dnscache.go b/net/dnscache/dnscache.go
index 5a5978f5f..0983ae875 100644
--- a/net/dnscache/dnscache.go
+++ b/net/dnscache/dnscache.go
@@ -21,6 +21,7 @@
 	"time"
 
 	"tailscale.com/envknob"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/cloudenv"
 	"tailscale.com/util/singleflight"
@@ -91,6 +92,11 @@ type Resolver struct {
 	// be added to all log messages printed with this logger.
 	Logf logger.Logf
 
+	// NetMon optionally provides a netmon.Monitor to use to get the current
+	// (cached) network interface.
+	// If nil, the interface will be looked up dynamically.
+	NetMon *netmon.Monitor
+
 	sf singleflight.Group[string, ipRes]
 
 	mu      sync.Mutex
diff --git a/net/dnsfallback/dnsfallback.go b/net/dnsfallback/dnsfallback.go
index 9ac22b9dc..5e80c79c9 100644
--- a/net/dnsfallback/dnsfallback.go
+++ b/net/dnsfallback/dnsfallback.go
@@ -23,6 +23,7 @@
 	"time"
 
 	"tailscale.com/atomicfile"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tshttpproxy"
@@ -31,13 +32,16 @@
 	"tailscale.com/util/slicesx"
 )
 
-func Lookup(logf logger.Logf) func(ctx context.Context, host string) ([]netip.Addr, error) {
+// MakeLookupFunc creates a function that can be used to resolve hostnames
+// (e.g. as a LookupIPFallback from dnscache.Resolver).
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func MakeLookupFunc(logf logger.Logf, netMon *netmon.Monitor) func(ctx context.Context, host string) ([]netip.Addr, error) {
 	return func(ctx context.Context, host string) ([]netip.Addr, error) {
-		return lookup(ctx, host, logf)
+		return lookup(ctx, host, logf, netMon)
 	}
 }
 
-func lookup(ctx context.Context, host string, logf logger.Logf) ([]netip.Addr, error) {
+func lookup(ctx context.Context, host string, logf logger.Logf, netMon *netmon.Monitor) ([]netip.Addr, error) {
 	if ip, err := netip.ParseAddr(host); err == nil && ip.IsValid() {
 		return []netip.Addr{ip}, nil
 	}
@@ -85,7 +89,7 @@ type nameIP struct {
 		logf("trying bootstrapDNS(%q, %q) for %q ...", cand.dnsName, cand.ip, host)
 		ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
 		defer cancel()
-		dm, err := bootstrapDNSMap(ctx, cand.dnsName, cand.ip, host, logf)
+		dm, err := bootstrapDNSMap(ctx, cand.dnsName, cand.ip, host, logf, netMon)
 		if err != nil {
 			logf("bootstrapDNS(%q, %q) for %q error: %v", cand.dnsName, cand.ip, host, err)
 			continue
@@ -104,8 +108,8 @@ type nameIP struct {
 
 // serverName and serverIP of are, say, "derpN.tailscale.com".
 // queryName is the name being sought (e.g. "controlplane.tailscale.com"), passed as hint.
-func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netip.Addr, queryName string, logf logger.Logf) (dnsMap, error) {
-	dialer := netns.NewDialer(logf)
+func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netip.Addr, queryName string, logf logger.Logf, netMon *netmon.Monitor) (dnsMap, error) {
+	dialer := netns.NewDialer(logf, netMon)
 	tr := http.DefaultTransport.(*http.Transport).Clone()
 	tr.Proxy = tshttpproxy.ProxyFromEnvironment
 	tr.DialContext = func(ctx context.Context, netw, addr string) (net.Conn, error) {
diff --git a/net/netcheck/netcheck.go b/net/netcheck/netcheck.go
index 687aa6a8b..a61343ebe 100644
--- a/net/netcheck/netcheck.go
+++ b/net/netcheck/netcheck.go
@@ -29,6 +29,7 @@
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/neterror"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/ping"
 	"tailscale.com/net/portmapper"
@@ -158,6 +159,11 @@ type Client struct {
 	// If nil, log.Printf is used.
 	Logf logger.Logf
 
+	// NetMon optionally provides a netmon.Monitor to use to get the current
+	// (cached) network interface.
+	// If nil, the interface will be looked up dynamically.
+	NetMon *netmon.Monitor
+
 	// TimeNow, if non-nil, is used instead of time.Now.
 	TimeNow func() time.Time
 
@@ -864,22 +870,29 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report,
 		return c.finishAndStoreReport(rs, dm), nil
 	}
 
-	ifState, err := interfaces.GetState()
-	if err != nil {
-		c.logf("[v1] interfaces: %v", err)
-		return nil, err
+	var ifState *interfaces.State
+	if c.NetMon == nil {
+		directState, err := interfaces.GetState()
+		if err != nil {
+			c.logf("[v1] interfaces: %v", err)
+			return nil, err
+		} else {
+			ifState = directState
+		}
+	} else {
+		ifState = c.NetMon.InterfaceState()
 	}
 
 	// See if IPv6 works at all, or if it's been hard disabled at the
 	// OS level.
-	v6udp, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp6", "[::1]:0")
+	v6udp, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf, c.NetMon)).ListenPacket(ctx, "udp6", "[::1]:0")
 	if err == nil {
 		rs.report.OSHasIPv6 = true
 		v6udp.Close()
 	}
 
 	// Create a UDP4 socket used for sending to our discovered IPv4 address.
-	rs.pc4Hair, err = nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp4", ":0")
+	rs.pc4Hair, err = nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf, c.NetMon)).ListenPacket(ctx, "udp4", ":0")
 	if err != nil {
 		c.logf("udp4: %v", err)
 		return nil, err
@@ -909,7 +922,7 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report,
 	if f := c.GetSTUNConn4; f != nil {
 		rs.pc4 = f()
 	} else {
-		u4, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp4", c.udpBindAddr())
+		u4, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf, nil)).ListenPacket(ctx, "udp4", c.udpBindAddr())
 		if err != nil {
 			c.logf("udp4: %v", err)
 			return nil, err
@@ -922,7 +935,7 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report,
 		if f := c.GetSTUNConn6; f != nil {
 			rs.pc6 = f()
 		} else {
-			u6, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, "udp6", c.udpBindAddr())
+			u6, err := nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf, nil)).ListenPacket(ctx, "udp6", c.udpBindAddr())
 			if err != nil {
 				c.logf("udp6: %v", err)
 			} else {
@@ -1297,7 +1310,7 @@ func (c *Client) measureAllICMPLatency(ctx context.Context, rs *reportState, nee
 	ctx, done := context.WithTimeout(ctx, icmpProbeTimeout)
 	defer done()
 
-	p, err := ping.New(ctx, c.logf)
+	p, err := ping.New(ctx, c.logf, c.NetMon)
 	if err != nil {
 		return err
 	}
@@ -1635,6 +1648,7 @@ func (c *Client) nodeAddr(ctx context.Context, n *tailcfg.DERPNode, proto probeP
 				Forward:     net.DefaultResolver,
 				UseLastGood: true,
 				Logf:        c.logf,
+				NetMon:      c.NetMon,
 			}
 		}
 		resolver := c.resolver
diff --git a/net/netns/netns.go b/net/netns/netns.go
index 86aafcac2..2acb15129 100644
--- a/net/netns/netns.go
+++ b/net/netns/netns.go
@@ -20,6 +20,7 @@
 	"sync/atomic"
 
 	"tailscale.com/net/netknob"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -55,19 +56,21 @@ func SetDisableBindConnToInterface(v bool) {
 // Listener returns a new net.Listener with its Control hook func
 // initialized as necessary to run in logical network namespace that
 // doesn't route back into Tailscale.
-func Listener(logf logger.Logf) *net.ListenConfig {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func Listener(logf logger.Logf, netMon *netmon.Monitor) *net.ListenConfig {
 	if disabled.Load() {
 		return new(net.ListenConfig)
 	}
-	return &net.ListenConfig{Control: control(logf)}
+	return &net.ListenConfig{Control: control(logf, netMon)}
 }
 
 // NewDialer returns a new Dialer using a net.Dialer with its Control
 // hook func initialized as necessary to run in a logical network
 // namespace that doesn't route back into Tailscale. It also handles
 // using a SOCKS if configured in the environment with ALL_PROXY.
-func NewDialer(logf logger.Logf) Dialer {
-	return FromDialer(logf, &net.Dialer{
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func NewDialer(logf logger.Logf, netMon *netmon.Monitor) Dialer {
+	return FromDialer(logf, netMon, &net.Dialer{
 		KeepAlive: netknob.PlatformTCPKeepAlive(),
 	})
 }
@@ -76,11 +79,12 @@ func NewDialer(logf logger.Logf) Dialer {
 // network namespace that doesn't route back into Tailscale. It also
 // handles using a SOCKS if configured in the environment with
 // ALL_PROXY.
-func FromDialer(logf logger.Logf, d *net.Dialer) Dialer {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func FromDialer(logf logger.Logf, netMon *netmon.Monitor, d *net.Dialer) Dialer {
 	if disabled.Load() {
 		return d
 	}
-	d.Control = control(logf)
+	d.Control = control(logf, netMon)
 	if wrapDialer != nil {
 		return wrapDialer(d)
 	}
diff --git a/net/netns/netns_android.go b/net/netns/netns_android.go
index 218b132e3..162e5c79a 100644
--- a/net/netns/netns_android.go
+++ b/net/netns/netns_android.go
@@ -10,6 +10,7 @@
 	"sync"
 	"syscall"
 
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -49,7 +50,7 @@ func SetAndroidProtectFunc(f func(fd int) error) {
 	androidProtectFunc = f
 }
 
-func control(logger.Logf) func(network, address string, c syscall.RawConn) error {
+func control(logger.Logf, *netmon.Monitor) func(network, address string, c syscall.RawConn) error {
 	return controlC
 }
 
diff --git a/net/netns/netns_darwin.go b/net/netns/netns_darwin.go
index c24c51102..7315dff40 100644
--- a/net/netns/netns_darwin.go
+++ b/net/netns/netns_darwin.go
@@ -19,24 +19,25 @@
 	"golang.org/x/sys/unix"
 	"tailscale.com/envknob"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
-func control(logf logger.Logf) func(network, address string, c syscall.RawConn) error {
+func control(logf logger.Logf, netMon *netmon.Monitor) func(network, address string, c syscall.RawConn) error {
 	return func(network, address string, c syscall.RawConn) error {
-		return controlLogf(logf, network, address, c)
+		return controlLogf(logf, netMon, network, address, c)
 	}
 }
 
 var bindToInterfaceByRouteEnv = envknob.RegisterBool("TS_BIND_TO_INTERFACE_BY_ROUTE")
 
-var errInterfaceIndexInvalid = errors.New("interface index invalid")
+var errInterfaceStateInvalid = errors.New("interface state invalid")
 
 // controlLogf marks c as necessary to dial in a separate network namespace.
 //
 // It's intentionally the same signature as net.Dialer.Control
 // and net.ListenConfig.Control.
-func controlLogf(logf logger.Logf, network, address string, c syscall.RawConn) error {
+func controlLogf(logf logger.Logf, netMon *netmon.Monitor, network, address string, c syscall.RawConn) error {
 	if isLocalhost(address) {
 		// Don't bind to an interface for localhost connections.
 		return nil
@@ -47,7 +48,7 @@ func controlLogf(logf logger.Logf, network, address string, c syscall.RawConn) e
 		return nil
 	}
 
-	idx, err := getInterfaceIndex(logf, address)
+	idx, err := getInterfaceIndex(logf, netMon, address)
 	if err != nil {
 		// callee logged
 		return nil
@@ -56,20 +57,31 @@ func controlLogf(logf logger.Logf, network, address string, c syscall.RawConn) e
 	return bindConnToInterface(c, network, address, idx, logf)
 }
 
-func getInterfaceIndex(logf logger.Logf, address string) (int, error) {
+func getInterfaceIndex(logf logger.Logf, netMon *netmon.Monitor, address string) (int, error) {
 	// Helper so we can log errors.
 	defaultIdx := func() (int, error) {
-		idx, err := interfaces.DefaultRouteInterfaceIndex()
-		if err != nil {
-			// It's somewhat common for there to be no default gateway route
-			// (e.g. on a phone with no connectivity), don't log those errors
-			// since they are expected.
-			if !errors.Is(err, interfaces.ErrNoGatewayIndexFound) {
-				logf("[unexpected] netns: DefaultRouteInterfaceIndex: %v", err)
+		if netMon == nil {
+			idx, err := interfaces.DefaultRouteInterfaceIndex()
+			if err != nil {
+				// It's somewhat common for there to be no default gateway route
+				// (e.g. on a phone with no connectivity), don't log those errors
+				// since they are expected.
+				if !errors.Is(err, interfaces.ErrNoGatewayIndexFound) {
+					logf("[unexpected] netns: DefaultRouteInterfaceIndex: %v", err)
+				}
+				return -1, err
 			}
-			return -1, err
+			return idx, nil
 		}
-		return idx, nil
+		state := netMon.InterfaceState()
+		if state == nil {
+			return -1, errInterfaceStateInvalid
+		}
+
+		if iface, ok := state.Interface[state.DefaultRouteInterface]; ok {
+			return iface.Index, nil
+		}
+		return -1, errInterfaceStateInvalid
 	}
 
 	useRoute := bindToInterfaceByRoute.Load() || bindToInterfaceByRouteEnv()
diff --git a/net/netns/netns_darwin_test.go b/net/netns/netns_darwin_test.go
index e1dc00b42..0fc92f6f3 100644
--- a/net/netns/netns_darwin_test.go
+++ b/net/netns/netns_darwin_test.go
@@ -34,7 +34,7 @@ func TestGetInterfaceIndex(t *testing.T) {
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
-			idx, err := getInterfaceIndex(t.Logf, tc.addr)
+			idx, err := getInterfaceIndex(t.Logf, nil, tc.addr)
 			if err != nil {
 				if tc.err == "" {
 					t.Fatalf("got unexpected error: %v", err)
@@ -68,7 +68,7 @@ func TestGetInterfaceIndex(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		idx, err := getInterfaceIndex(t.Logf, "100.100.100.100:53")
+		idx, err := getInterfaceIndex(t.Logf, nil, "100.100.100.100:53")
 		if err != nil {
 			t.Fatal(err)
 		}
diff --git a/net/netns/netns_default.go b/net/netns/netns_default.go
index 43a573959..94f24d8fa 100644
--- a/net/netns/netns_default.go
+++ b/net/netns/netns_default.go
@@ -8,10 +8,11 @@
 import (
 	"syscall"
 
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
-func control(logger.Logf) func(network, address string, c syscall.RawConn) error {
+func control(logger.Logf, *netmon.Monitor) func(network, address string, c syscall.RawConn) error {
 	return controlC
 }
 
diff --git a/net/netns/netns_linux.go b/net/netns/netns_linux.go
index dea6a9e8d..5d09d7d19 100644
--- a/net/netns/netns_linux.go
+++ b/net/netns/netns_linux.go
@@ -15,6 +15,7 @@
 	"golang.org/x/sys/unix"
 	"tailscale.com/envknob"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -85,7 +86,7 @@ func ignoreErrors() bool {
 	return false
 }
 
-func control(logger.Logf) func(network, address string, c syscall.RawConn) error {
+func control(logger.Logf, *netmon.Monitor) func(network, address string, c syscall.RawConn) error {
 	return controlC
 }
 
diff --git a/net/netns/netns_test.go b/net/netns/netns_test.go
index d95c04981..82f919b94 100644
--- a/net/netns/netns_test.go
+++ b/net/netns/netns_test.go
@@ -24,7 +24,7 @@ func TestDial(t *testing.T) {
 	if !*extNetwork {
 		t.Skip("skipping test without --use-external-network")
 	}
-	d := NewDialer(t.Logf)
+	d := NewDialer(t.Logf, nil)
 	c, err := d.Dial("tcp", "google.com:80")
 	if err != nil {
 		t.Fatal(err)
diff --git a/net/netns/netns_windows.go b/net/netns/netns_windows.go
index 147a762ec..8aa1da18d 100644
--- a/net/netns/netns_windows.go
+++ b/net/netns/netns_windows.go
@@ -12,6 +12,7 @@
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 	"tailscale.com/types/logger"
 )
 
@@ -26,7 +27,7 @@ func interfaceIndex(iface *winipcfg.IPAdapterAddresses) uint32 {
 	return iface.IfIndex
 }
 
-func control(logger.Logf) func(network, address string, c syscall.RawConn) error {
+func control(logger.Logf, *netmon.Monitor) func(network, address string, c syscall.RawConn) error {
 	return controlC
 }
 
diff --git a/net/ping/ping.go b/net/ping/ping.go
index f4bd7f0e0..9b9618e0f 100644
--- a/net/ping/ping.go
+++ b/net/ping/ping.go
@@ -18,6 +18,7 @@
 
 	"golang.org/x/net/icmp"
 	"golang.org/x/net/ipv4"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/types/logger"
 )
@@ -52,8 +53,9 @@ type Pinger struct {
 
 // New creates a new Pinger. The Context provided will be used to create
 // network listeners, and to set an absolute deadline (if any) on the net.Conn
-func New(ctx context.Context, logf logger.Logf) (*Pinger, error) {
-	p, err := newUnstarted(ctx, logf)
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func New(ctx context.Context, logf logger.Logf, netMon *netmon.Monitor) (*Pinger, error) {
+	p, err := newUnstarted(ctx, logf, netMon)
 	if err != nil {
 		return nil, err
 	}
@@ -72,14 +74,14 @@ func New(ctx context.Context, logf logger.Logf) (*Pinger, error) {
 	return p, nil
 }
 
-func newUnstarted(ctx context.Context, logf logger.Logf) (*Pinger, error) {
+func newUnstarted(ctx context.Context, logf logger.Logf, netMon *netmon.Monitor) (*Pinger, error) {
 	var id [2]byte
 	_, err := rand.Read(id[:])
 	if err != nil {
 		return nil, err
 	}
 
-	conn, err := netns.Listener(logf).ListenPacket(ctx, "ip4:icmp", "0.0.0.0")
+	conn, err := netns.Listener(logf, netMon).ListenPacket(ctx, "ip4:icmp", "0.0.0.0")
 	if err != nil {
 		return nil, err
 	}
diff --git a/net/portmapper/igd_test.go b/net/portmapper/igd_test.go
index f48959631..57c0d7aa6 100644
--- a/net/portmapper/igd_test.go
+++ b/net/portmapper/igd_test.go
@@ -249,7 +249,7 @@ func (d *TestIGD) handlePCPQuery(pkt []byte, src netip.AddrPort) {
 
 func newTestClient(t *testing.T, igd *TestIGD) *Client {
 	var c *Client
-	c = NewClient(t.Logf, nil, func() {
+	c = NewClient(t.Logf, nil, nil, func() {
 		t.Logf("port map changed")
 		t.Logf("have mapping: %v", c.HaveMapping())
 	})
diff --git a/net/portmapper/portmapper.go b/net/portmapper/portmapper.go
index 2d8c06591..2e500b555 100644
--- a/net/portmapper/portmapper.go
+++ b/net/portmapper/portmapper.go
@@ -21,6 +21,7 @@
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/neterror"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/types/logger"
@@ -59,6 +60,7 @@ type DebugKnobs struct {
 // Client is a port mapping client.
 type Client struct {
 	logf         logger.Logf
+	netMon       *netmon.Monitor // optional; nil means interfaces will be looked up on-demand
 	ipAndGateway func() (gw, ip netip.Addr, ok bool)
 	onChange     func() // or nil
 	debug        DebugKnobs
@@ -153,15 +155,19 @@ func (m *pmpMapping) Release(ctx context.Context) {
 
 // NewClient returns a new portmapping client.
 //
+// The netMon parameter is optional; if non-nil it's used to do faster interface
+// lookups.
+//
 // The debug argument allows configuring the behaviour of the portmapper for
 // debugging; if nil, a sensible set of defaults will be used.
 //
 // The optional onChange argument specifies a func to run in a new
 // goroutine whenever the port mapping status has changed. If nil,
 // it doesn't make a callback.
-func NewClient(logf logger.Logf, debug *DebugKnobs, onChange func()) *Client {
+func NewClient(logf logger.Logf, netMon *netmon.Monitor, debug *DebugKnobs, onChange func()) *Client {
 	ret := &Client{
 		logf:         logf,
+		netMon:       netMon,
 		ipAndGateway: interfaces.LikelyHomeRouterIP,
 		onChange:     onChange,
 	}
@@ -271,7 +277,7 @@ func (c *Client) listenPacket(ctx context.Context, network, addr string) (nettyp
 		}
 		return pc.(*net.UDPConn), nil
 	}
-	pc, err := netns.Listener(c.logf).ListenPacket(ctx, network, addr)
+	pc, err := netns.Listener(c.logf, c.netMon).ListenPacket(ctx, network, addr)
 	if err != nil {
 		return nil, err
 	}
diff --git a/net/portmapper/portmapper_test.go b/net/portmapper/portmapper_test.go
index 67c37f8bd..15f2849fc 100644
--- a/net/portmapper/portmapper_test.go
+++ b/net/portmapper/portmapper_test.go
@@ -16,7 +16,7 @@ func TestCreateOrGetMapping(t *testing.T) {
 	if v, _ := strconv.ParseBool(os.Getenv("HIT_NETWORK")); !v {
 		t.Skip("skipping test without HIT_NETWORK=1")
 	}
-	c := NewClient(t.Logf, nil, nil)
+	c := NewClient(t.Logf, nil, nil, nil)
 	defer c.Close()
 	c.SetLocalPort(1234)
 	for i := 0; i < 2; i++ {
@@ -32,7 +32,7 @@ func TestClientProbe(t *testing.T) {
 	if v, _ := strconv.ParseBool(os.Getenv("HIT_NETWORK")); !v {
 		t.Skip("skipping test without HIT_NETWORK=1")
 	}
-	c := NewClient(t.Logf, nil, nil)
+	c := NewClient(t.Logf, nil, nil, nil)
 	defer c.Close()
 	for i := 0; i < 3; i++ {
 		if i > 0 {
@@ -47,7 +47,7 @@ func TestClientProbeThenMap(t *testing.T) {
 	if v, _ := strconv.ParseBool(os.Getenv("HIT_NETWORK")); !v {
 		t.Skip("skipping test without HIT_NETWORK=1")
 	}
-	c := NewClient(t.Logf, nil, nil)
+	c := NewClient(t.Logf, nil, nil, nil)
 	defer c.Close()
 	c.SetLocalPort(1234)
 	res, err := c.Probe(context.Background())
diff --git a/net/portmapper/upnp.go b/net/portmapper/upnp.go
index 5844d7428..6a525c54f 100644
--- a/net/portmapper/upnp.go
+++ b/net/portmapper/upnp.go
@@ -237,7 +237,7 @@ func (c *Client) upnpHTTPClientLocked() *http.Client {
 	if c.uPnPHTTPClient == nil {
 		c.uPnPHTTPClient = &http.Client{
 			Transport: &http.Transport{
-				DialContext:     netns.NewDialer(c.logf).DialContext,
+				DialContext:     netns.NewDialer(c.logf, c.netMon).DialContext,
 				IdleConnTimeout: 2 * time.Second, // LAN is cheap
 			},
 		}
diff --git a/net/sockstats/sockstats.go b/net/sockstats/sockstats.go
index e968ac7bf..b39d60afb 100644
--- a/net/sockstats/sockstats.go
+++ b/net/sockstats/sockstats.go
@@ -109,8 +109,8 @@ func GetValidation() *ValidationSockStats {
 
 // SetNetMon configures the sockstats package to monitor the active
 // interface, so that per-interface stats can be collected.
-func SetNetMon(lm *netmon.Monitor) {
-	setNetMon(lm)
+func SetNetMon(netMon *netmon.Monitor) {
+	setNetMon(netMon)
 }
 
 // DebugInfo returns a string containing debug information about the tracked
diff --git a/net/sockstats/sockstats_noop.go b/net/sockstats/sockstats_noop.go
index 46b5ceaef..96723111a 100644
--- a/net/sockstats/sockstats_noop.go
+++ b/net/sockstats/sockstats_noop.go
@@ -30,7 +30,7 @@ func getValidation() *ValidationSockStats {
 	return nil
 }
 
-func setNetMon(lm *netmon.Monitor) {
+func setNetMon(netMon *netmon.Monitor) {
 }
 
 func debugInfo() string {
diff --git a/net/sockstats/sockstats_tsgo.go b/net/sockstats/sockstats_tsgo.go
index e2dd05f22..26211958f 100644
--- a/net/sockstats/sockstats_tsgo.go
+++ b/net/sockstats/sockstats_tsgo.go
@@ -249,13 +249,13 @@ func getValidation() *ValidationSockStats {
 	return r
 }
 
-func setNetMon(lm *netmon.Monitor) {
+func setNetMon(netMon *netmon.Monitor) {
 	sockStats.mu.Lock()
 	defer sockStats.mu.Unlock()
 
 	// We intentionally populate all known interfaces now, so that we can
 	// increment stats for them without holding mu.
-	state := lm.InterfaceState()
+	state := netMon.InterfaceState()
 	for ifName, iface := range state.Interface {
 		sockStats.knownInterfaces[iface.Index] = ifName
 	}
@@ -266,7 +266,7 @@ func setNetMon(lm *netmon.Monitor) {
 		sockStats.usedInterfaces[ifIndex] = 1
 	}
 
-	lm.RegisterChangeCallback(func(changed bool, state *interfaces.State) {
+	netMon.RegisterChangeCallback(func(changed bool, state *interfaces.State) {
 		if changed {
 			if ifName := state.DefaultRouteInterface; ifName != "" {
 				ifIndex := state.Interface[ifName].Index
diff --git a/net/tsdial/tsdial.go b/net/tsdial/tsdial.go
index bb1dde397..54e91ca13 100644
--- a/net/tsdial/tsdial.go
+++ b/net/tsdial/tsdial.go
@@ -128,14 +128,14 @@ func (d *Dialer) Close() error {
 	return nil
 }
 
-func (d *Dialer) SetNetMon(mon *netmon.Monitor) {
+func (d *Dialer) SetNetMon(netMon *netmon.Monitor) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 	if d.netMonUnregister != nil {
 		go d.netMonUnregister()
 		d.netMonUnregister = nil
 	}
-	d.netMon = mon
+	d.netMon = netMon
 	d.netMonUnregister = d.netMon.RegisterChangeCallback(d.linkChanged)
 }
 
@@ -279,7 +279,7 @@ func (d *Dialer) SystemDial(ctx context.Context, network, addr string) (net.Conn
 		if logf == nil {
 			logf = logger.Discard
 		}
-		d.netnsDialer = netns.NewDialer(logf)
+		d.netnsDialer = netns.NewDialer(logf, d.netMon)
 	})
 	c, err := d.netnsDialer.DialContext(ctx, network, addr)
 	if err != nil {
diff --git a/prober/derp.go b/prober/derp.go
index 21583a9bf..cd267e27e 100644
--- a/prober/derp.go
+++ b/prober/derp.go
@@ -346,7 +346,7 @@ func newConn(ctx context.Context, dm *tailcfg.DERPMap, n *tailcfg.DERPNode) (*de
 		return !strings.Contains(s, "derphttp.Client.Connect: connecting to")
 	})
 	priv := key.NewNode()
-	dc := derphttp.NewRegionClient(priv, l, func() *tailcfg.DERPRegion {
+	dc := derphttp.NewRegionClient(priv, l, nil /* no netMon */, func() *tailcfg.DERPRegion {
 		rid := n.RegionID
 		return &tailcfg.DERPRegion{
 			RegionID:   rid,
diff --git a/tsnet/tsnet.go b/tsnet/tsnet.go
index 6e7db9440..2bea9026b 100644
--- a/tsnet/tsnet.go
+++ b/tsnet/tsnet.go
@@ -203,7 +203,7 @@ func (s *Server) Loopback() (addr string, proxyCred, localAPICred string, err er
 		// out the CONNECT code from tailscaled/proxy.go that uses
 		// httputil.ReverseProxy and adding auth support.
 		go func() {
-			lah := localapi.NewHandler(s.lb, s.logf, s.logid)
+			lah := localapi.NewHandler(s.lb, s.logf, s.netMon, s.logid)
 			lah.PermitWrite = true
 			lah.PermitRead = true
 			lah.RequiredPassword = s.localAPICred
@@ -564,7 +564,7 @@ func (s *Server) start() (reterr error) {
 	go s.printAuthURLLoop()
 
 	// Run the localapi handler, to allow fetching LetsEncrypt certs.
-	lah := localapi.NewHandler(lb, logf, s.logid)
+	lah := localapi.NewHandler(lb, logf, s.netMon, s.logid)
 	lah.PermitWrite = true
 	lah.PermitRead = true
 
@@ -620,7 +620,7 @@ func (s *Server) startLogger(closePool *closeOnErrorPool) error {
 			}
 			return w
 		},
-		HTTPC: &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost)},
+		HTTPC: &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost, s.netMon)},
 	}
 	s.logtail = logtail.NewLogger(c, s.logf)
 	closePool.addFunc(func() { s.logtail.Shutdown(context.Background()) })
diff --git a/wgengine/magicsock/magicsock.go b/wgengine/magicsock/magicsock.go
index 5a0a2bf0d..123b2e70b 100644
--- a/wgengine/magicsock/magicsock.go
+++ b/wgengine/magicsock/magicsock.go
@@ -642,7 +642,7 @@ func NewConn(opts Options) (*Conn, error) {
 	c.idleFunc = opts.IdleFunc
 	c.testOnlyPacketListener = opts.TestOnlyPacketListener
 	c.noteRecvActivity = opts.NoteRecvActivity
-	c.portMapper = portmapper.NewClient(logger.WithPrefix(c.logf, "portmapper: "), nil, c.onPortMapChanged)
+	c.portMapper = portmapper.NewClient(logger.WithPrefix(c.logf, "portmapper: "), opts.NetMon, nil, c.onPortMapChanged)
 	if opts.NetMon != nil {
 		c.portMapper.SetGatewayLookupFunc(opts.NetMon.GatewayAndSelfIP)
 	}
@@ -656,6 +656,7 @@ func NewConn(opts Options) (*Conn, error) {
 	c.donec = c.connCtx.Done()
 	c.netChecker = &netcheck.Client{
 		Logf:                logger.WithPrefix(c.logf, "netcheck: "),
+		NetMon:              c.netMon,
 		GetSTUNConn4:        func() netcheck.STUNConn { return &c.pconn4 },
 		GetSTUNConn6:        func() netcheck.STUNConn { return &c.pconn6 },
 		SkipExternalNetwork: inTest(),
@@ -1554,7 +1555,7 @@ func (c *Conn) derpWriteChanOfAddr(addr netip.AddrPort, peer key.NodePublic) cha
 
 	// Note that derphttp.NewRegionClient does not dial the server
 	// (it doesn't block) so it is safe to do under the c.mu lock.
-	dc := derphttp.NewRegionClient(c.privateKey, c.logf, func() *tailcfg.DERPRegion {
+	dc := derphttp.NewRegionClient(c.privateKey, c.logf, c.netMon, func() *tailcfg.DERPRegion {
 		// Warning: it is not legal to acquire
 		// magicsock.Conn.mu from this callback.
 		// It's run from derphttp.Client.connect (via Send, etc)
@@ -3251,7 +3252,7 @@ func (c *Conn) listenPacket(network string, port uint16) (nettype.PacketConn, er
 	if c.testOnlyPacketListener != nil {
 		return nettype.MakePacketListenerWithNetIP(c.testOnlyPacketListener).ListenPacket(ctx, network, addr)
 	}
-	return nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf)).ListenPacket(ctx, network, addr)
+	return nettype.MakePacketListenerWithNetIP(netns.Listener(c.logf, c.netMon)).ListenPacket(ctx, network, addr)
 }
 
 var debugBindSocket = envknob.RegisterBool("TS_DEBUG_MAGICSOCK_BIND_SOCKET")
diff --git a/wgengine/netlog/logger.go b/wgengine/netlog/logger.go
index bb3f667a3..a694308e6 100644
--- a/wgengine/netlog/logger.go
+++ b/wgengine/netlog/logger.go
@@ -19,6 +19,7 @@
 	"tailscale.com/logpolicy"
 	"tailscale.com/logtail"
 	"tailscale.com/net/connstats"
+	"tailscale.com/net/netmon"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/smallzstd"
@@ -91,7 +92,8 @@ func (nl *Logger) Running() bool {
 // is a non-tailscale IP address to contact for that particular tailscale node.
 // The IP protocol and source port are always zero.
 // The sock is used to populated the PhysicalTraffic field in Message.
-func (nl *Logger) Startup(nodeID tailcfg.StableNodeID, nodeLogID, domainLogID logid.PrivateID, tun, sock Device) error {
+// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
+func (nl *Logger) Startup(nodeID tailcfg.StableNodeID, nodeLogID, domainLogID logid.PrivateID, tun, sock Device, netMon *netmon.Monitor) error {
 	nl.mu.Lock()
 	defer nl.mu.Unlock()
 	if nl.logger != nil {
@@ -99,7 +101,7 @@ func (nl *Logger) Startup(nodeID tailcfg.StableNodeID, nodeLogID, domainLogID lo
 	}
 
 	// Startup a log stream to Tailscale's logging service.
-	httpc := &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost)}
+	httpc := &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost, netMon)}
 	if testClient != nil {
 		httpc = testClient
 	}
diff --git a/wgengine/userspace.go b/wgengine/userspace.go
index c7caf1492..1356b36df 100644
--- a/wgengine/userspace.go
+++ b/wgengine/userspace.go
@@ -917,7 +917,7 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
 		nid := cfg.NetworkLogging.NodeID
 		tid := cfg.NetworkLogging.DomainID
 		e.logf("wgengine: Reconfig: starting up network logger (node:%s tailnet:%s)", nid.Public(), tid.Public())
-		if err := e.networkLogger.Startup(cfg.NodeID, nid, tid, e.tundev, e.magicConn); err != nil {
+		if err := e.networkLogger.Startup(cfg.NodeID, nid, tid, e.tundev, e.magicConn, e.netMon); err != nil {
 			e.logf("wgengine: Reconfig: error starting up network logger: %v", err)
 		}
 		e.networkLogger.ReconfigRoutes(routerCfg)