diff --git a/pkg/registry/core/service/ipallocator/allocator.go b/pkg/registry/core/service/ipallocator/allocator.go
index dd206eb1d0..e8c28bf374 100644
--- a/pkg/registry/core/service/ipallocator/allocator.go
+++ b/pkg/registry/core/service/ipallocator/allocator.go
@@ -263,8 +263,8 @@ func calculateIPOffset(base *big.Int, ip net.IP) int {
 // RangeSize returns the size of a range in valid addresses.
 func RangeSize(subnet *net.IPNet) int64 {
 	ones, bits := subnet.Mask.Size()
-	if (bits - ones) >= 31 {
-		panic("masks greater than 31 bits are not supported")
+	if bits == 32 && (bits-ones) >= 31 || bits == 128 && (bits-ones) >= 63 {
+		return 0
 	}
 	max := int64(1) << uint(bits-ones)
 	return max
diff --git a/pkg/registry/core/service/ipallocator/allocator_test.go b/pkg/registry/core/service/ipallocator/allocator_test.go
index ff854ce31b..481a4d41b6 100644
--- a/pkg/registry/core/service/ipallocator/allocator_test.go
+++ b/pkg/registry/core/service/ipallocator/allocator_test.go
@@ -166,18 +166,41 @@ func TestAllocateSmall(t *testing.T) {
 }
 
 func TestRangeSize(t *testing.T) {
-	testCases := map[string]int64{
-		"192.168.1.0/24": 256,
-		"192.168.1.0/32": 1,
-		"192.168.1.0/31": 2,
+	testCases := []struct {
+		name  string
+		cidr  string
+		addrs int64
+	}{
+		{
+			name:  "supported IPv4 cidr",
+			cidr:  "192.168.1.0/24",
+			addrs: 256,
+		},
+		{
+			name:  "unsupported IPv4 cidr",
+			cidr:  "192.168.1.0/1",
+			addrs: 0,
+		},
+		{
+			name:  "supported IPv6 cidr",
+			cidr:  "2001:db8::/98",
+			addrs: 1073741824,
+		},
+		{
+			name:  "unsupported IPv6 mask",
+			cidr:  "2001:db8::/65",
+			addrs: 0,
+		},
 	}
-	for k, v := range testCases {
-		_, cidr, err := net.ParseCIDR(k)
+
+	for _, tc := range testCases {
+		_, cidr, err := net.ParseCIDR(tc.cidr)
 		if err != nil {
-			t.Fatal(err)
+			t.Errorf("failed to parse cidr for test %s, unexpected error: '%s'", tc.name, err)
 		}
-		if size := RangeSize(cidr); size != v {
-			t.Errorf("%s should have a range size of %d, got %d", k, v, size)
+		if size := RangeSize(cidr); size != tc.addrs {
+			t.Errorf("test %s failed. %s should have a range size of %d, got %d",
+				tc.name, tc.cidr, tc.addrs, size)
 		}
 	}
 }