diff --git a/agent/consul/internal_endpoint.go b/agent/consul/internal_endpoint.go
index 074f7ffe09..5a165737af 100644
--- a/agent/consul/internal_endpoint.go
+++ b/agent/consul/internal_endpoint.go
@@ -8,6 +8,7 @@ import (
 	"net"
 
 	hashstructure_v2 "github.com/mitchellh/hashstructure/v2"
+	"golang.org/x/exp/maps"
 
 	"github.com/hashicorp/go-bexpr"
 	"github.com/hashicorp/go-hclog"
@@ -778,11 +779,10 @@ func (m *Internal) AssignManualServiceVIPs(args *structs.AssignServiceManualVIPs
 		if parsedIP == nil || parsedIP.To4() == nil {
 			return fmt.Errorf("%q is not a valid IPv4 address", parsedIP.String())
 		}
-		if _, ok := vipMap[ip]; ok {
-			return fmt.Errorf("duplicate manual ip found: %q", ip)
-		}
 		vipMap[ip] = struct{}{}
 	}
+	// Silently ignore duplicates.
+	args.ManualVIPs = maps.Keys(vipMap)
 
 	psn := structs.PeeredServiceName{
 		ServiceName: structs.NewServiceName(args.Service, &args.EnterpriseMeta),
diff --git a/agent/consul/internal_endpoint_test.go b/agent/consul/internal_endpoint_test.go
index c5a8a76fb0..caa32393c9 100644
--- a/agent/consul/internal_endpoint_test.go
+++ b/agent/consul/internal_endpoint_test.go
@@ -3721,6 +3721,7 @@ func TestInternal_AssignManualServiceVIPs(t *testing.T) {
 		expect      structs.AssignServiceManualVIPsResponse
 		expectAgain structs.AssignServiceManualVIPsResponse
 		expectErr   string
+		expectIPs   []string
 	}
 
 	run := func(t *testing.T, tc testcase, again bool) {
@@ -3741,6 +3742,12 @@ func TestInternal_AssignManualServiceVIPs(t *testing.T) {
 			} else {
 				require.Equal(t, tc.expect, resp)
 			}
+
+			psn := structs.PeeredServiceName{ServiceName: structs.NewServiceName(tc.req.Service, nil)}
+			got, err := s1.fsm.State().ServiceManualVIPs(psn)
+			require.NoError(t, err)
+			require.NotNil(t, got)
+			require.Equal(t, tc.expectIPs, got.ManualIPs)
 		}
 	}
 
@@ -3751,6 +3758,17 @@ func TestInternal_AssignManualServiceVIPs(t *testing.T) {
 				Service:    "web",
 				ManualVIPs: []string{"1.1.1.1", "2.2.2.2"},
 			},
+			expectIPs:   []string{"1.1.1.1", "2.2.2.2"},
+			expect:      structs.AssignServiceManualVIPsResponse{Found: true},
+			expectAgain: structs.AssignServiceManualVIPsResponse{Found: true},
+		},
+		{
+			name: "successfully ignoring duplicates",
+			req: structs.AssignServiceManualVIPsRequest{
+				Service:    "web",
+				ManualVIPs: []string{"1.2.3.4", "5.6.7.8", "1.2.3.4", "5.6.7.8"},
+			},
+			expectIPs:   []string{"1.2.3.4", "5.6.7.8"},
 			expect:      structs.AssignServiceManualVIPsResponse{Found: true},
 			expectAgain: structs.AssignServiceManualVIPsResponse{Found: true},
 		},
@@ -3760,6 +3778,7 @@ func TestInternal_AssignManualServiceVIPs(t *testing.T) {
 				Service:    "web",
 				ManualVIPs: []string{"8.8.8.8"},
 			},
+			expectIPs: []string{"8.8.8.8"},
 			expect: structs.AssignServiceManualVIPsResponse{
 				Found: true,
 				UnassignedFrom: []structs.PeeredServiceName{
@@ -3777,7 +3796,6 @@ func TestInternal_AssignManualServiceVIPs(t *testing.T) {
 				Service:    "web",
 				ManualVIPs: []string{"3.3.3.3", "invalid"},
 			},
-			expect:    structs.AssignServiceManualVIPsResponse{},
 			expectErr: "not a valid",
 		},
 	}