diff --git a/lib/utils/ip.js b/lib/utils/ip.js
index f92fadd7..6b977db4 100644
--- a/lib/utils/ip.js
+++ b/lib/utils/ip.js
@@ -30,38 +30,61 @@ var ipv6Regex =
  */
 
 IP.parseHost = function parseHost(addr, fallback) {
-  var port = fallback || 0;
-  var parts, host, version;
+  var parts, host, port, version;
 
   assert(typeof addr === 'string');
-  assert(typeof port === 'number');
 
   assert(addr.length > 0, 'Bad address.');
 
-  // [ipv6]:port
   if (addr[0] === '[') {
-    addr = addr.substring(1);
-    parts = addr.split(/\]:?/);
-    assert(parts.length === 2, 'Bad IPv6 address.');
+    if (addr[addr.length - 1] === ']') {
+      // Case:
+      // [::1]
+      host = addr.slice(1, -1);
+      port = null;
+    } else {
+      // Case:
+      // [::1]:80
+      addr = addr.slice(1);
+      parts = addr.split(']:');
+      assert(parts.length === 2, 'Bad IPv6 address.');
+      host = parts[0];
+      port = parts[1];
+    }
   } else {
     parts = addr.split(':');
-    if (parts.length > 2) {
-      // ipv6 - no port
-      assert(IP.isV6Format(addr), 'Bad IPv6 address.');
-      parts = [addr];
-    } else {
-      // domain/ipv4:port?
-      assert(parts.length <= 2, 'Bad host.');
+    switch (parts.length) {
+      case 2:
+        // Cases:
+        // 127.0.0.1:80
+        // localhost:80
+        host = parts[0];
+        port = parts[1];
+        break;
+      case 1:
+        // Cases:
+        // 127.0.0.1
+        // localhost
+        host = parts[0];
+        port = null;
+        break;
+      default:
+        // Case:
+        // ::1
+        assert(IP.isV6Format(addr), 'Bad IPv6 address.');
+        host = addr;
+        port = null;
+        break;
     }
   }
 
-  host = parts[0];
   assert(host.length > 0, 'Bad host.');
 
-  if (parts.length === 2) {
-    port = parts[1];
+  if (port != null) {
     assert(/^\d+$/.test(port), 'Bad port.');
     port = parseInt(port, 10);
+  } else {
+    port = fallback || 0;
   }
 
   version = IP.version(host);
@@ -90,6 +113,9 @@ IP.hostname = function hostname(host, port) {
 
   version = IP.version(host);
 
+  if (host.indexOf(':') !== -1)
+    assert(version === 6, 'Bad host.');
+
   if (version !== -1)
     host = IP.normalize(host);
 
@@ -126,6 +152,10 @@ IP.version = function version(str) {
 IP.isV4Format = function(str) {
   if (str.length < 7)
     return false;
+
+  if (str.length > 15)
+    return false;
+
   return ipv4Regex.test(str);
 };
 
@@ -136,6 +166,12 @@ IP.isV4Format = function(str) {
  */
 
 IP.isV6Format = function(str) {
+  if (str.length < 2)
+    return false;
+
+  if (str.length > 39)
+    return false;
+
   return ipv6Regex.test(str);
 };