diff --git a/Data/IP.hs b/Data/IP.hs
--- a/Data/IP.hs
+++ b/Data/IP.hs
@@ -5,8 +5,8 @@
   -- * Documentation
   -- ** IP data
     IP (..)
-  , IPv4, toIPv4, fromIPv4
-  , IPv6, toIPv6, fromIPv6
+  , IPv4, toIPv4, fromIPv4, fromHostAddress, toHostAddress
+  , IPv6, toIPv6, fromIPv6, fromHostAddress6, toHostAddress6
   -- ** IP range data
   , IPRange (..)
   , AddrRange (addr, mask, mlen)
diff --git a/Data/IP/Addr.hs b/Data/IP/Addr.hs
--- a/Data/IP/Addr.hs
+++ b/Data/IP/Addr.hs
@@ -6,6 +6,8 @@
 import Data.List (foldl')
 import Data.String
 import Data.Word
+import Network.Socket
+import System.ByteOrder
 import Text.Appar.String
 import Text.Printf
 
@@ -122,7 +124,7 @@
 --
 
 {-|
-  The 'fromIPv4' function convert 'IPv4' to a list of 'Int'.
+  The 'fromIPv4' function converts 'IPv4' to a list of 'Int'.
 
 >>> fromIPv4 (toIPv4 [192,0,2,1])
 [192,0,2,1]
@@ -131,7 +133,7 @@
 fromIPv4 (IP4 w) = map (\n -> fromEnum $ (w `shiftR` n) .&. 0xff) [0o30, 0o20, 0o10, 0o00]
 
 {-|
-  The 'toIPv6' function convert 'IPv6' to a list of 'Int'.
+  The 'toIPv6' function converts 'IPv6' to a list of 'Int'.
 
 >>> fromIPv6 (toIPv6 [0x2001,0xDB8,0,0,0,0,0,1])
 [8193,3512,0,0,0,0,0,1]
@@ -250,3 +252,36 @@
                           let spring = replicate len 0
                           return $ bs1 ++ spring ++ bs2
       check bs = when (length bs /= 8) (fail "IPv6 address4")
+
+----------------------------------------------------------------
+--
+-- HostAddress and HostAddress6
+--
+
+-- | The 'fromHostAddress' function converts 'HostAddress' to 'IPv4'.
+fromHostAddress :: HostAddress -> IPv4
+fromHostAddress addr4
+  | byteOrder == LittleEndian = IP4 $ fixByteOrder addr4
+  | otherwise                 = IP4 addr4
+
+-- | The 'toHostAddress' function converts 'IPv4' to 'HostAddress'.
+toHostAddress :: IPv4 -> HostAddress
+toHostAddress (IP4 addr4)
+  | byteOrder == LittleEndian = fixByteOrder addr4
+  | otherwise                 = addr4
+
+-- | The 'fromHostAddress6' function converts 'HostAddress6' to 'IPv6'.
+fromHostAddress6 :: HostAddress6 -> IPv6
+fromHostAddress6 addr6 = IP6 addr6
+
+-- | The 'toHostAddress6' function converts 'IPv6' to 'HostAddress6'.
+toHostAddress6 :: IPv6 -> HostAddress6
+toHostAddress6 (IP6 addr6) = addr6
+
+fixByteOrder :: Word32 -> Word32
+fixByteOrder s = d1 .|. d2 .|. d3 .|. d4
+  where
+    d1 = shiftL s 24
+    d2 = shiftL s  8 .&. 0x00ff0000
+    d3 = shiftR s  8 .&. 0x0000ff00
+    d4 = shiftR s 24 .&. 0x000000ff
diff --git a/Data/IP/RouteTable/Internal.hs b/Data/IP/RouteTable/Internal.hs
--- a/Data/IP/RouteTable/Internal.hs
+++ b/Data/IP/RouteTable/Internal.hs
@@ -89,6 +89,9 @@
 
 {-|
   The 'empty' function returns an empty IP routing table.
+
+>>> (empty :: IPRTable IPv4 ()) == fromList []
+True
 -}
 empty :: Routable k => IPRTable k a
 empty = Nil
@@ -147,7 +150,7 @@
   The 'delete' function deletes a value by a key of 'AddrRange' from 'IPRTable'
   and returns a new 'IPRTable'.
 
->>> delete "127.0.0.1" (insert ("127.0.0.1" :: AddrRange IPv4) () empty) == empty
+>>> delete "127.0.0.1" (insert "127.0.0.1" () empty) == (empty :: IPRTable IPv4 ())
 True
 -}
 delete :: (Routable k) => AddrRange k -> IPRTable k a -> IPRTable k a
diff --git a/iproute.cabal b/iproute.cabal
--- a/iproute.cabal
+++ b/iproute.cabal
@@ -1,5 +1,5 @@
 Name:                   iproute
-Version:                1.2.5
+Version:                1.2.6
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -27,7 +27,11 @@
                         Data.IP.Op
                         Data.IP.Range
                         Data.IP.RouteTable.Internal
-  Build-Depends:        base >= 4 && < 5, appar, containers
+  Build-Depends:        base >= 4 && < 5
+                      , appar
+                      , byteorder
+                      , containers
+                      , network
 Source-Repository head
   Type:                 git
   Location:             git://github.com/kazu-yamamoto/iproute.git