diff --git a/appc/appconnector.go b/appc/appconnector.go
index 9b8398811..d60d0198c 100644
--- a/appc/appconnector.go
+++ b/appc/appconnector.go
@@ -206,9 +206,8 @@ func (e *AppConnector) ObserveDNSResponse(res []byte) {
 		if slices.Contains(addrs, addr) {
 			continue
 		}
-		// TODO(raggi): check for existing prefixes
 		if err := e.routeAdvertiser.AdvertiseRoute(netip.PrefixFrom(addr, addr.BitLen())); err != nil {
-			e.logf("failed to advertise route for %v: %v", addr, err)
+			e.logf("failed to advertise route for %s: %v: %v", domain, addr, err)
 			continue
 		}
 		e.logf("[v2] advertised route for %v: %v", domain, addr)
@@ -217,5 +216,4 @@ func (e *AppConnector) ObserveDNSResponse(res []byte) {
 		e.domains[domain] = append(addrs, addr)
 		e.mu.Unlock()
 	}
-
 }
diff --git a/ipn/ipnlocal/local.go b/ipn/ipnlocal/local.go
index 1c81ba045..4f72a305e 100644
--- a/ipn/ipnlocal/local.go
+++ b/ipn/ipnlocal/local.go
@@ -774,7 +774,7 @@ func (b *LocalBackend) UpdateStatus(sb *ipnstate.StatusBuilder) {
 				}
 				if !prefs.ExitNodeID().IsZero() {
 					if exitPeer, ok := b.netMap.PeerWithStableID(prefs.ExitNodeID()); ok {
-						var online = false
+						online := false
 						if v := exitPeer.Online(); v != nil {
 							online = *v
 						}
@@ -855,7 +855,7 @@ func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
 		if p.LastSeen() != nil {
 			lastSeen = *p.LastSeen()
 		}
-		var tailscaleIPs = make([]netip.Addr, 0, p.Addresses().Len())
+		tailscaleIPs := make([]netip.Addr, 0, p.Addresses().Len())
 		for i := range p.Addresses().LenIter() {
 			addr := p.Addresses().At(i)
 			if addr.IsSingleIP() && tsaddr.IsTailscaleIP(addr.Addr()) {
@@ -4200,7 +4200,6 @@ func (b *LocalBackend) enterStateLockedOnEntry(newState ipn.State) {
 	default:
 		b.logf("[unexpected] unknown newState %#v", newState)
 	}
-
 }
 
 // hasNodeKey reports whether a non-zero node key is present in the current
@@ -5781,12 +5780,21 @@ func (b *LocalBackend) ObserveDNSResponse(res []byte) {
 	appConnector.ObserveDNSResponse(res)
 }
 
+// ErrDisallowedAutoRoute is returned by AdvertiseRoute when a route that is not allowed is requested.
+var ErrDisallowedAutoRoute = errors.New("route is not allowed")
+
 // AdvertiseRoute implements the appc.RouteAdvertiser interface. It sets a new
 // route advertisement if one is not already present in the existing routes.
+// If the route is disallowed, ErrDisallowedAutoRoute is returned.
 func (b *LocalBackend) AdvertiseRoute(ipp netip.Prefix) error {
+	if !allowedAutoRoute(ipp) {
+		return ErrDisallowedAutoRoute
+	}
 	currentRoutes := b.Prefs().AdvertiseRoutes()
-	// TODO(raggi): check if the new route is a subset of an existing route.
-	if currentRoutes.ContainsFunc(func(r netip.Prefix) bool { return r == ipp }) {
+	if currentRoutes.ContainsFunc(func(r netip.Prefix) bool {
+		// TODO(raggi): add support for subset checks and avoid subset route creations.
+		return ipp.IsSingleIP() && r.Contains(ipp.Addr()) || r == ipp
+	}) {
 		return nil
 	}
 	routes := append(currentRoutes.AsSlice(), ipp)
@@ -5799,6 +5807,36 @@ func (b *LocalBackend) AdvertiseRoute(ipp netip.Prefix) error {
 	return err
 }
 
+var (
+	disallowedAddrs = []netip.Addr{
+		netip.MustParseAddr("::1"),
+		netip.MustParseAddr("::"),
+		netip.MustParseAddr("0.0.0.0"),
+	}
+	disallowedRanges = []netip.Prefix{
+		netip.MustParsePrefix("127.0.0.0/8"),
+		netip.MustParsePrefix("224.0.0.0/4"),
+		netip.MustParsePrefix("ff00::/8"),
+	}
+)
+
+// allowedAutoRoute determines if the route being added via AdvertiseRoute (the app connector featuge) should be allowed.
+func allowedAutoRoute(ipp netip.Prefix) bool {
+	// Note: blocking the addrs for globals, not solely the prefixes.
+	for _, addr := range disallowedAddrs {
+		if ipp.Addr() == addr {
+			return false
+		}
+	}
+	for _, pfx := range disallowedRanges {
+		if pfx.Overlaps(ipp) {
+			return false
+		}
+	}
+	// TODO(raggi): exclude tailscale service IPs and so on as well.
+	return true
+}
+
 // mayDeref dereferences p if non-nil, otherwise it returns the zero value.
 func mayDeref[T any](p *T) (v T) {
 	if p == nil {
diff --git a/ipn/ipnlocal/local_test.go b/ipn/ipnlocal/local_test.go
index 71d08822b..17d374866 100644
--- a/ipn/ipnlocal/local_test.go
+++ b/ipn/ipnlocal/local_test.go
@@ -265,7 +265,6 @@ func TestPeerRoutes(t *testing.T) {
 			}
 		})
 	}
-
 }
 
 func TestPeerAPIBase(t *testing.T) {
@@ -700,7 +699,6 @@ func TestPacketFilterPermitsUnlockedNodes(t *testing.T) {
 			}
 		})
 	}
-
 }
 
 func TestStatusWithoutPeers(t *testing.T) {
@@ -1173,6 +1171,26 @@ func TestRouteAdvertiser(t *testing.T) {
 	}
 }
 
+func TestRouterAdvertiserIgnoresContainedRoutes(t *testing.T) {
+	b := newTestBackend(t)
+	testPrefix := netip.MustParsePrefix("192.0.0.0/24")
+	ra := appc.RouteAdvertiser(b)
+	must.Do(ra.AdvertiseRoute(testPrefix))
+
+	routes := b.Prefs().AdvertiseRoutes()
+	if routes.Len() != 1 || routes.At(0) != testPrefix {
+		t.Fatalf("got routes %v, want %v", routes, []netip.Prefix{testPrefix})
+	}
+
+	must.Do(ra.AdvertiseRoute(netip.MustParsePrefix("192.0.0.8/32")))
+
+	// the above /32 is not added as it is contained within the /24
+	routes = b.Prefs().AdvertiseRoutes()
+	if routes.Len() != 1 || routes.At(0) != testPrefix {
+		t.Fatalf("got routes %v, want %v", routes, []netip.Prefix{testPrefix})
+	}
+}
+
 func TestObserveDNSResponse(t *testing.T) {
 	b := newTestBackend(t)
 
@@ -1886,7 +1904,6 @@ func TestApplySysPolicy(t *testing.T) {
 			})
 
 			t.Run("set prefs", func(t *testing.T) {
-
 				b := newTestBackend(t)
 				b.SetPrefs(tt.prefs.Clone())
 				if !b.Prefs().Equals(tt.wantPrefs.View()) {