diff --git a/Data/IP/RouteTable.hs b/Data/IP/RouteTable.hs
--- a/Data/IP/RouteTable.hs
+++ b/Data/IP/RouteTable.hs
@@ -17,6 +17,7 @@
   -- ** Functions to manipulate an IP routing table
   , empty, insert, delete
   , I.lookup
+  , I.lookupKeyValue
   , findMatch
   , fromList, toList
   ) where
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
@@ -212,9 +212,29 @@
 Just 133.5.16.0/24
 -}
 lookup :: Routable k => AddrRange k -> IPRTable k a -> Maybe a
-lookup k s = search k s Nothing
+lookup k s = fmap snd (search k s Nothing)
 
-search :: Routable k => AddrRange k -> IPRTable k a -> Maybe a -> Maybe a
+{-|
+  The 'lookupKeyValue' function looks up 'IPRTable' with a key of 'AddrRange'.
+  If a routing information in 'IPRTable' matches the key, both key and value
+  are returned.
+
+>>> :set -XOverloadedStrings
+>>> let rt = fromList ([("192.168.0.0/24", 1), ("10.10.0.0/16", 2)] :: [(AddrRange IPv4, Int)])
+>>> lookupKeyValue "127.0.0.1" rt
+Nothing
+>>> lookupKeyValue "192.168.0.1" rt
+Just (192.168.0.0/24,1)
+>>> lookupKeyValue "10.10.0.1" rt
+Just (10.10.0.0/16,2)
+-}
+lookupKeyValue :: Routable k => AddrRange k -> IPRTable k a -> Maybe (AddrRange k, a)
+lookupKeyValue k s = search k s Nothing
+
+search :: Routable k => AddrRange k
+                     -> IPRTable k a
+                     -> Maybe (AddrRange k, a)
+                     -> Maybe (AddrRange k, a)
 search _ Nil res = res
 search k1 (Node k2 tb2 Nothing l r) res
   | k1 == k2  = res
@@ -223,12 +243,12 @@
                   else
                     search k1 r res
   | otherwise = res
-search k1 (Node k2 tb2 vl l r) res
-  | k1 == k2  = vl
+search k1 (Node k2 tb2 (Just vl) l r) res
+  | k1 == k2  = Just (k1, vl)
   | k2 >:> k1 = if isLeft k1 tb2 then
-                    search k1 l vl
+                    search k1 l $ Just (k2, vl)
                   else
-                    search k1 r vl
+                    search k1 r $ Just (k2, vl)
   | otherwise = res
 
 ----------------------------------------------------------------
diff --git a/iproute.cabal b/iproute.cabal
--- a/iproute.cabal
+++ b/iproute.cabal
@@ -1,5 +1,5 @@
 Name:                   iproute
-Version:                1.7.1
+Version:                1.7.2
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3