<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML ><HEAD ><TITLE >Addresses without a special prefix</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="Linux IPv6 HOWTO (en)" HREF="index.html"><LINK REL="UP" TITLE="Address types" HREF="chapter-addresstypes.html"><LINK REL="PREVIOUS" TITLE="Address types" HREF="chapter-addresstypes.html"><LINK REL="NEXT" TITLE="Network part, also known as prefix" HREF="x512.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Linux IPv6 HOWTO (en)</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="chapter-addresstypes.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 3. Address types</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x512.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN475" ></A >3.1. Addresses without a special prefix</H1 ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN477" ></A >3.1.1. Localhost address</H2 ><P >This is a special address for the loopback interface, similiar to IPv4 with its “127.0.0.1”. With IPv6, the localhost address is:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >0000:0000:0000:0000:0000:0000:0000:0001 </PRE ></FONT ></TD ></TR ></TABLE ><P >or compressed:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >::1</PRE ></FONT ></TD ></TR ></TABLE ><P >Packets with this address as source or destination should never leave the sending host.</P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN484" ></A >3.1.2. Unspecified address</H2 ><P >This is a special address like “any” or “0.0.0.0” in IPv4 . For IPv6 it's:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >0000:0000:0000:0000:0000:0000:0000:0000 </PRE ></FONT ></TD ></TR ></TABLE ><P >or:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >::</PRE ></FONT ></TD ></TR ></TABLE ><P >These addresses are mostly used/seen in socket binding (to any IPv6 address) or routing tables.</P ><P >Note: the unspecified address cannot be used as destination address.</P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="AEN492" ></A >3.1.3. IPv6 address with embedded IPv4 address</H2 ><P >There are two addresses which contain an IPv4 address.</P ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN495" ></A >3.1.3.1. IPv4-mapped IPv6 address</H3 ><P >IPv4-only IPv6-compatible addresses are sometimes used/shown for sockets created by an IPv6-enabled daemon, but only binding to an IPv4 address.</P ><P >These addresses are defined with a special prefix of length 96 (a.b.c.d is the IPv4 address):</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >0:0:0:0:0:ffff:a.b.c.d/96</PRE ></FONT ></TD ></TR ></TABLE ><P >or in compressed format</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >::ffff:a.b.c.d/96</PRE ></FONT ></TD ></TR ></TABLE ><P >For example, the IPv4 address 1.2.3.4 looks like this:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >::ffff:1.2.3.4</PRE ></FONT ></TD ></TR ></TABLE ></DIV ><DIV CLASS="SECT3" ><H3 CLASS="SECT3" ><A NAME="AEN504" ></A >3.1.3.2. IPv4-compatible IPv6 address</H3 ><P >Used for automatic tunneling (<A HREF="http://www.faqs.org/rfcs/rfc2893.html" TARGET="_top" >RFC 2893 / Transition Mechanisms for IPv6 Hosts and Routers</A >), which is being replaced by <A HREF="x1193.html#TUNNELING-6TO4." >6to4 tunneling</A >.</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >0:0:0:0:0:0:a.b.c.d/96</PRE ></FONT ></TD ></TR ></TABLE ><P >or in compressed format</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >::a.b.c.d/96</PRE ></FONT ></TD ></TR ></TABLE ></DIV ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="chapter-addresstypes.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x512.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Address types</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="chapter-addresstypes.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Network part, also known as prefix</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
