<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<!-- saved from url=(0014)about:internet -->
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Style-Type" content="text/css" />
    <meta name="GENERATOR" content="Quadralay WebWorks AutoMap 2003 Platinum Edition Client for FrameMaker 8.6.6597.0" />
    <meta name="TEMPLATEBASE" content="emwebh8-1-17" />
    <meta name="LASTUPDATED" content="08/01/13 14:48:20" />
    <title>Global Addresses </title>
    <!-- Copyright 2010-2013, Cisco Systems, Inc. All rights reserved. -->

    <link rel="StyleSheet" href="document.css" type="text/css" />
    <link rel="StyleSheet" href="catalog.css" type="text/css" />


<script> 
    var is_chrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1; 
   
    if(is_chrome){document.domain=document.domain}
   </script>
    <script type="text/javascript" language="JavaScript1.2" src="expand.js"></script>
    <script type="text/javascript" language="JavaScript1.2" src="page.js"></script>

    <script type="text/javascript" language="JavaScript1.2">
     <!--
      function  WWNoOp() {}
      function  WWNoValue() { return ""; }

      var  VarDropDown;

      if (typeof(HTMLHelp_Object) != "undefined")
      {
        VarDropDown = new WWDropDown_Object();
      }
      else
      {
        VarDropDown = new Object();
        VarDropDown.fAnchorOpen  = WWNoOp;
        VarDropDown.fAnchorClose = WWNoOp;
        VarDropDown.fDIVOpen  = WWNoOp;
        VarDropDown.fDIVClose = WWNoOp;
      }
     // -->
    </script>

  
<SCRIPT language="javascript">
<!--
  self.document.write("<link href='"+top.relPath+"shared/style.css' rel='stylesheet' type='text/css'>");
  myid=2169;
  self.document.write("<script type='text/javascript' language='JavaScript' src='"+top.relPath+"shared/con_utils.js'></scr"+"ipt>");
//-->
</SCRIPT>
</head>

  <body onload="highlightSearchTerms();" bgcolor="#ffffff">

    
    <blockquote>
    <a name="top"></a>

    
    


<a name="wp1073007"> </a><h1 class="pTitle">
Global Addresses

</h1>
<a name="wp1073018"> </a><p class="pBody">
Global IPv6 addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Addresses 
with a prefix of 2000::/3 (001) through E000::/3 (111) are required to have 64-bit interface identifiers in 
the extended universal identifier (EUI)-64 format. The Internet Assigned Numbers Authority (IANA) 
allocates the IPv6 address space in the range of 2000::/16 to regional registries.

</p>
<a name="wp1073019"> </a><p class="pBody">
The aggregatable global address typically consists of a 48-bit global routing prefix and a 16-bit subnet 
ID or Site-Level Aggregator (SLA). In the IPv6 aggregatable global unicast address format document 
(RFC 2374), the global routing prefix included two other hierarchically structured fields named 
Top-Level Aggregator (TLA) and Next-Level Aggregator (NLA).The IETF decided to remove the TLS 
and NLA fields from the RFCs because these fields are policy-based. Some existing IPv6 networks 
deployed before the change might still be using networks based on the older architecture.

</p>
<a name="wp1073020"> </a><p class="pBody">
A 16-bit subnet field called the subnet ID could be used by individual organizations to create their own 
local addressing hierarchy and to identify subnets. A subnet ID is similar to a subnet in IPv4, except that 
an organization with an IPv6 subnet ID can support up to 65,535 individual subnets.

</p>
<a name="wp1073021"> </a><p class="pBody">
An interface ID is used to identify interfaces on a link. The interface ID must be unique to the link. They 
may also be unique over a broader scope. In many cases, an interface ID will be the same as, or based 
on, the link-layer address of an interface, which results in a globally unique interface ID. Interface IDs 
used in aggregatable global unicast and other IPv6 address types must be 64 bits long and constructed 
in the modified EUI-64 format. 

</p>
<a name="wp1073022"> </a><p class="pBody">
Cisco MDS NX-OS supports IEEE 802 interface types (for example, Gigabit Ethernet interfaces). The 
first three octets (24&#160;bits) are taken from the Organizationally Unique Identifier (OUI) of the 48-bit 
link-layer address (MAC address) of the interface, the fourth and fifth octets (16&#160;bits) are a fixed 
hexadecimal value of FFFE, and the last three octets (24&#160;bits) are taken from the last three octets of the 
MAC address. The construction of the interface ID is completed by setting the Universal/Local (U/L) 
bit&#8212;the seventh bit of the first octet&#8212;to a value of 0 or 1. A value of 0 indicates a locally administered 
identifier; a value of 1 indicates a globally unique IPv6 interface identifier . 

</p>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

    </blockquote>

  </body>
</html>
