diff --git a/radius.cabal b/radius.cabal
--- a/radius.cabal
+++ b/radius.cabal
@@ -1,5 +1,5 @@
 name:                radius
-version:             0.6.0.1
+version:             0.6.0.2
 synopsis:            Remote Authentication Dial In User Service (RADIUS)
 description:         This module provides types and on the wire de/coding of RADIUS packets as per RFC2865
 homepage:            https://gitlab.com/codemonkeylabs/RADIUS
diff --git a/src/Network/RADIUS/Encoding.hs b/src/Network/RADIUS/Encoding.hs
--- a/src/Network/RADIUS/Encoding.hs
+++ b/src/Network/RADIUS/Encoding.hs
@@ -209,6 +209,14 @@
       putWord8 attrLen
       putWord8 identity
       putLazyByteString str
+    put (DelegatedIPv6Prefix prefixLength prefix) = do
+      let attr    = encode prefix
+          attrLen = 4 + (fromIntegral . B.length $ attr)
+      putWord8 123 -- Attribute type
+      putWord8 attrLen
+      putWord8 0 -- reserved
+      putWord8 $ fromIntegral prefixLength
+      putLazyByteString attr
     put (UnknownAttribute attributeType value) = putAttribute attributeType value
 
     get = do
@@ -325,6 +333,14 @@
   identity <- getWord8
   attrData <- getLazyByteString 16 -- CHAP response is always 16 octets
   return $ CHAPPassword identity attrData
+getAttribute 123 = do
+  attrLen      <- getWord8
+  when (attrLen /= 20) $ fail $ "Unsupported RADIUS Delegated IPv6 Prefix attribute length "
+           ++ show attrLen
+  _reserved    <- getWord8
+  prefixLength <- getWord8
+  prefix       <- get
+  return $ DelegatedIPv6Prefix (fromIntegral prefixLength) prefix
 getAttribute n  = getAttributeStr >>= return . UnknownAttribute n
 
 -- | For internal use.
diff --git a/src/Network/RADIUS/Types.hs b/src/Network/RADIUS/Types.hs
--- a/src/Network/RADIUS/Types.hs
+++ b/src/Network/RADIUS/Types.hs
@@ -92,6 +92,8 @@
   | ReplyMessageAttribute           { getReplyMessageAttribute           :: ByteString        }
   | CallbackNumberAttribute         { getCallbackNumberAttribute         :: ByteString        }
   | CallbackIdAttribute             { getCallbackIdAttribute             :: ByteString        }
+  | DelegatedIPv6Prefix             { getDelegatedIPv6PrefixLength       :: Int8,
+                                      getDelegatedIPv6Prefix             :: IPv6              }
   | FramedRouteAttribute            { getFramedRouteAttribute            :: ByteString        }
   | FramedIPXNetworkAttribute       { getFramedIPXNetworkAttribute       :: Word32            }
   | StateAttribute                  { getStateAttribute                  :: ByteString        }