diff --git a/lib/ip.js b/lib/ip.js
index c1799a8..6cbeed9 100644
--- a/lib/ip.js
+++ b/lib/ip.js
@@ -313,6 +313,11 @@ ip.isPrivate = function(addr) {
     /^::$/.test(addr);
 };
 
+ip.isShared = function(addr) {
+  return /^(::f{4}:)?100\.64\.([0-9]{1,3})\.([0-9]{1,3})$/i
+      .test(addr);
+};
+
 ip.isPublic = function(addr) {
   return !ip.isPrivate(addr);
 };
diff --git a/test/api-test.js b/test/api-test.js
index 2e390f9..c6d4fe9 100644
--- a/test/api-test.js
+++ b/test/api-test.js
@@ -293,6 +293,16 @@ describe('IP library for node.js', function() {
     });
   });
 
+  describe('isShared() method', function() {
+    it('should check if an address is in the shared address space', function() {
+      assert.equal(ip.isShared('100.64.0.1'), true);
+    });
+
+    it('should not detect 100.* as the shared address space', function() {
+      assert.equal(ip.isShared('100.6.0.1'), false);
+    });
+  });
+
   describe('loopback() method', function() {
     describe('undefined', function() {
       it('should respond with 127.0.0.1', function() {