diff --git a/Lib/ipaddress.py b/Lib/ipaddress.py
index 7a3f36f3bc0..909a55de4f1 100644
--- a/Lib/ipaddress.py
+++ b/Lib/ipaddress.py
@@ -532,6 +532,30 @@ class _IPAddressBase:
         except ValueError:
             cls._report_invalid_netmask(ip_str)
 
+    @classmethod
+    def _split_addr_prefix(cls, address):
+        """Helper function to parse address of Network/Interface.
+
+        Arg:
+            address: Argument of Network/Interface.
+
+        Returns:
+            (addr, prefix) tuple.
+        """
+        # a packed address or integer
+        if isinstance(address, (bytes, int)):
+            return address, cls._max_prefixlen
+
+        if not isinstance(address, tuple):
+            # Assume input argument to be string or any object representation
+            # which converts into a formatted IP prefix string.
+            address = _split_optional_netmask(address)
+
+        # Constructing from a tuple (addr, [mask])
+        if len(address) > 1:
+            return address
+        return address[0], cls._max_prefixlen
+
     def __reduce__(self):
         return self.__class__, (str(self),)
 
@@ -1305,32 +1329,16 @@ class IPv4Address(_BaseV4, _BaseAddress):
 class IPv4Interface(IPv4Address):
 
     def __init__(self, address):
-        if isinstance(address, (bytes, int)):
-            IPv4Address.__init__(self, address)
-            self.network = IPv4Network(self._ip)
-            self._prefixlen = self._max_prefixlen
-            return
+        addr, mask = self._split_addr_prefix(address)
 
-        if isinstance(address, tuple):
-            IPv4Address.__init__(self, address[0])
-            if len(address) > 1:
-                self._prefixlen = int(address[1])
-            else:
-                self._prefixlen = self._max_prefixlen
-
-            self.network = IPv4Network(address, strict=False)
-            self.netmask = self.network.netmask
-            self.hostmask = self.network.hostmask
-            return
-
-        addr = _split_optional_netmask(address)
-        IPv4Address.__init__(self, addr[0])
-
-        self.network = IPv4Network(address, strict=False)
+        IPv4Address.__init__(self, addr)
+        self.network = IPv4Network((addr, mask), strict=False)
+        self.netmask = self.network.netmask
         self._prefixlen = self.network._prefixlen
 
-        self.netmask = self.network.netmask
-        self.hostmask = self.network.hostmask
+    @functools.cached_property
+    def hostmask(self):
+        return self.network.hostmask
 
     def __str__(self):
         return '%s/%d' % (self._string_from_ip_int(self._ip),
@@ -1435,20 +1443,7 @@ class IPv4Network(_BaseV4, _BaseNetwork):
             ValueError: If strict is True and a network address is not
               supplied.
         """
-        # Constructing from a packed address or integer
-        if isinstance(address, (int, bytes)):
-            addr = address
-            mask = self._max_prefixlen
-        # Constructing from a tuple (addr, [mask])
-        elif isinstance(address, tuple):
-            addr = address[0]
-            mask = address[1] if len(address) > 1 else self._max_prefixlen
-        # Assume input argument to be string or any object representation
-        # which converts into a formatted IP prefix string.
-        else:
-            args = _split_optional_netmask(address)
-            addr = self._ip_int_from_string(args[0])
-            mask = args[1] if len(args) == 2 else self._max_prefixlen
+        addr, mask = self._split_addr_prefix(address)
 
         self.network_address = IPv4Address(addr)
         self.netmask, self._prefixlen = self._make_netmask(mask)
@@ -1979,28 +1974,16 @@ class IPv6Address(_BaseV6, _BaseAddress):
 class IPv6Interface(IPv6Address):
 
     def __init__(self, address):
-        if isinstance(address, (bytes, int)):
-            IPv6Address.__init__(self, address)
-            self.network = IPv6Network(self._ip)
-            self._prefixlen = self._max_prefixlen
-            return
-        if isinstance(address, tuple):
-            IPv6Address.__init__(self, address[0])
-            if len(address) > 1:
-                self._prefixlen = int(address[1])
-            else:
-                self._prefixlen = self._max_prefixlen
-            self.network = IPv6Network(address, strict=False)
-            self.netmask = self.network.netmask
-            self.hostmask = self.network.hostmask
-            return
+        addr, mask = self._split_addr_prefix(address)
 
-        addr = _split_optional_netmask(address)
-        IPv6Address.__init__(self, addr[0])
-        self.network = IPv6Network(address, strict=False)
+        IPv6Address.__init__(self, addr)
+        self.network = IPv6Network((addr, mask), strict=False)
         self.netmask = self.network.netmask
         self._prefixlen = self.network._prefixlen
-        self.hostmask = self.network.hostmask
+
+    @functools.cached_property
+    def hostmask(self):
+        return self.network.hostmask
 
     def __str__(self):
         return '%s/%d' % (self._string_from_ip_int(self._ip),
@@ -2110,20 +2093,7 @@ class IPv6Network(_BaseV6, _BaseNetwork):
             ValueError: If strict was True and a network address was not
               supplied.
         """
-        # Constructing from a packed address or integer
-        if isinstance(address, (int, bytes)):
-            addr = address
-            mask = self._max_prefixlen
-        # Constructing from a tuple (addr, [mask])
-        elif isinstance(address, tuple):
-            addr = address[0]
-            mask = address[1] if len(address) > 1 else self._max_prefixlen
-        # Assume input argument to be string or any object representation
-        # which converts into a formatted IP prefix string.
-        else:
-            args = _split_optional_netmask(address)
-            addr = self._ip_int_from_string(args[0])
-            mask = args[1] if len(args) == 2 else self._max_prefixlen
+        addr, mask = self._split_addr_prefix(address)
 
         self.network_address = IPv6Address(addr)
         self.netmask, self._prefixlen = self._make_netmask(mask)
diff --git a/Lib/test/test_ipaddress.py b/Lib/test/test_ipaddress.py
index 15317c94463..20316f15f8c 100644
--- a/Lib/test/test_ipaddress.py
+++ b/Lib/test/test_ipaddress.py
@@ -399,7 +399,13 @@ class NetmaskTestMixin_v4(CommonTestMixin_v4):
     """Input validation on interfaces and networks is very similar"""
 
     def test_no_mask(self):
-        self.assertEqual(str(self.factory('1.2.3.4')), '1.2.3.4/32')
+        for address in ('1.2.3.4', 0x01020304, b'\x01\x02\x03\x04'):
+            net = self.factory(address)
+            self.assertEqual(str(net), '1.2.3.4/32')
+            self.assertEqual(str(net.netmask), '255.255.255.255')
+            self.assertEqual(str(net.hostmask), '0.0.0.0')
+            # IPv4Network has prefixlen, but IPv4Interface doesn't.
+            # Should we add it to IPv4Interface too? (bpo-36392)
 
     def test_split_netmask(self):
         addr = "1.2.3.4/32/24"
@@ -527,6 +533,15 @@ class NetworkTestCase_v4(BaseTestCase, NetmaskTestMixin_v4):
 class NetmaskTestMixin_v6(CommonTestMixin_v6):
     """Input validation on interfaces and networks is very similar"""
 
+    def test_no_mask(self):
+        for address in ('::1', 1, b'\x00'*15 + b'\x01'):
+            net = self.factory(address)
+            self.assertEqual(str(net), '::1/128')
+            self.assertEqual(str(net.netmask), 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff')
+            self.assertEqual(str(net.hostmask), '::')
+            # IPv6Network has prefixlen, but IPv6Interface doesn't.
+            # Should we add it to IPv4Interface too? (bpo-36392)
+
     def test_split_netmask(self):
         addr = "cafe:cafe::/128/190"
         with self.assertAddressError("Only one '/' permitted in %r" % addr):