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+
+<head>
+<meta http-equiv="Content-Language" content="en-us">
+<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
+
+
+
+<title>Content</title>
+<base target="_self">
+</head>
+
+<body background="../../images/bg.gif" topmargin="0" leftmargin="0" marginheight="0" marginwidth="0" onLoad="window.focus();" link="#808080" vlink="#808080" alink="#808080">
+
+<table border="0" cellpadding="0" cellspacing="0" width="100%">
+ <tr>
+ <td bgcolor="#336666" width="18" valign="top">
+ <img border="0" src="../../images/content_lines.gif" width="16" height="25">
+ <img border="0" src="../../images/transdot.gif" width="2" height="1"></td>
+ <td bgcolor="#336666"><font face="Arial" size="2" color="#FFFFFF"><b>1.1</b></font></td>
+ <td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#336666" width="100%">
+ <b><font face="Arial" size="2" color="#FFFFFF">Scaling Networks with NAT
+ and PAT</font></b></td>
+ <td width="9" bgcolor="#336666"> </td>
+ </tr>
+ <tr>
+ <td bgcolor="#669999" height="25" width="18"> </td>
+ <td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
+ 1.1.6</font></b></td>
+ <td bgcolor="#669999"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
+ <td bgcolor="#669999" height="25" width="100%"><b>
+ <font face="Arial" size="2" color="#FFFFFF">Troubleshooting NAT and PAT
+ configuration</font></b></td>
+ <td bgcolor="#669999" height="25" width="9"> </td>
+ </tr></table>
+
+<table border="0" cellpadding="0" cellspacing="0" width="95%" bordercolor="#111111">
+ <tr>
+ <td width="15"></td>
+ <td>
+
+ <font FACE="Arial" SIZE="2">
+ When IP connectivity problems in a NAT environment exist, it is often
+ difficult to determine the cause of the problem. Many times NAT is
+ mistakenly blamed, when in reality there is an underlying problem.</font><p>
+
+ <font FACE="Arial" SIZE="2">
+ When trying to determine the cause of an IP connectivity problem, it
+ helps to rule out NAT. Use the following steps to determine whether
+ NAT is operating as expected:</p>
+ <ol>
+ <li>Based on the configuration, clearly define what NAT is supposed
+ to achieve.</li>
+ <li>Verify that correct translations exist in the translation table. </li>
+ <li>Verify the translation is occurring by using </font>
+
+ <font FACE="Courier New" SIZE="2">
+ <b>show</b></font><font FACE="Arial" SIZE="2">
+ and </font>
+
+ <font FACE="Courier New" SIZE="2">
+ <b>debug</b></font><font FACE="Arial" SIZE="2">
+ commands. </li>
+ <li>Review in detail what is happening to the packet and verify that
+ routers have the correct routing information to move the packet
+ along.</font></li>
+ </ol>
+ <p>
+
+ <font FACE="Arial" SIZE="2">
+ Use the </font>
+
+ <font FACE="Courier New" SIZE="2">
+ <b>debug ip nat</b></font><font FACE="Arial" SIZE="2">
+ command to verify the operation of the NAT
+ feature by displaying information about every packet that is
+ translated by the router. The </font><font FACE="Courier New" SIZE="2"><b>debug ip nat
+ <i>detailed</i></b></font><font FACE="Arial" SIZE="2">
+ command generates
+ a description of each packet considered for translation. This command
+ also outputs information about certain errors or exception conditions,
+ such as the failure to allocate a global address.</font></p>
+ <p>
+
+ <font FACE="Arial" SIZE="2">
+ Figure <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> shows
+ a sample
+ </font>
+
+ <font FACE="Courier New" SIZE="2">
+ <b>debug ip nat</b></font><font FACE="Arial" SIZE="2">
+ output. In this example, the
+ first two lines of the debugging output show that a Domain Name System
+ (DNS) request and reply were produced. The remaining lines show the
+ debugging output of a Telnet connection from a host on the inside of
+ the network to a host on the outside of the network.
+ </font>
+ </p>
+ <p>
+
+ <font FACE="Arial" SIZE="2">
+ Decode the
+ </font>
+
+ <font FACE="Courier New" SIZE="2">
+ <b>debug</b></font><font FACE="Arial" SIZE="2">
+ output by using the following key points:
+ </font>
+ </p>
+ <ul>
+ <li>
+
+ <font FACE="Arial" SIZE="2">
+ The asterisk next to NAT indicates that the translation is occurring
+ in the fast-switched path. The first packet in a conversation will
+ always go through the slow path, which means this first packet is
+ process-switched. The remaining packets will go through the
+ fast-switched path if a cache entry exists.
+ </font>
+ </li>
+ <li>
+
+ <font FACE="Arial" SIZE="2">
+ s = a.b.c.d<b> </b> is the source address.
+ </font>
+ </li>
+ <li>
+
+ <font face="Arial" size="2">Source address a.b.c.d is translated to
+ w.x.y.z. </font>
+ </li>
+ <li>
+
+ <font face="Arial" size="2">d = e.f.g.h is the destination address.
+ </font>
+ </li>
+ <li>
+
+ <font FACE="Arial" SIZE="2">
+ The value in brackets is the IP identification number. This
+ information may be useful for debugging. This is useful, for
+ example, because it enables correlation with other packet traces
+ from protocol analyzers.
+ </font>
+ </li>
+ </ul>
+ <p>
+ <TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
+ <TR>
+ <TD valign="top">
+ <TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD width="5">
+ <img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
+ <TD>
+ <IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
+ <IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
+ </TR>
+ </TABLE>
+
+ <TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD>
+ <TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
+ <TR>
+ <TD bgcolor="#ffffff" width="15"> </TD>
+ <TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">
+
+ <a target="main" href="../lab1_1_6/index.html">
+
+ <img border="0" src="../../images/lab_icon.gif" width="25" height="25"> <b>
+ Lab Activity</b></a></font></p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#808080">
+ <p>Lab Exercise: Troubleshooting NAT and PAT</p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">In this lab, the student will configure
+ a router for Network Address Translation (NAT) and Port Address
+ Translation (PAT). </font></p>
+ <p></TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+
+
+
+ <TABLE bgcolor="#669999" width="95%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD width="5">
+ <img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
+ <TD>
+ <IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
+ <IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
+ </TR>
+ </TABLE>
+
+ <TABLE bgcolor="#B0AFAF" width="95%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD>
+ <TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
+ <TR>
+ <TD bgcolor="#ffffff" width="15"> </TD>
+ <TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">
+
+ <a href="javascript:void(0)" onClick="window.open('../../elabs/mod01/elab_1_1_6/elab1_1_6.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');">
+ <img border="0" src="../../images/lab_icon.gif" width="25" height="25"><b></a>
+ <a href="javascript:void(0)" onClick="window.open('../../elabs/mod01/elab_1_1_6/elab1_1_6.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');">Lab Activity</a></b></font></p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#808080">
+ <p>e-Lab Activity: Troubleshooting NAT and PAT</p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">In this lab, the student will configure
+ a router for Network Address Translation and Port Address
+ Translation.</font></p>
+ <p></TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+
+
+
+ <TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
+ <TR>
+ <TD valign="top">
+ <TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD width="5">
+ <img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
+ <TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
+ <IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
+ </TR>
+ </TABLE>
+
+ <TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
+ <TR>
+ <TD>
+ <TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
+ <TR>
+ <TD bgcolor="#ffffff" width="15"> </TD>
+ <TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">
+ <img border="0" src="../../images/links_icon.gif" width="25" height="25">
+ <b>Web Links</b></font></p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#808080">
+
+ <p>Verifying NAT Operation and Basic NAT Troubleshooting<p>
+ <a target="_blank" href="http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094c32.shtml">
+ http://www.cisco.com/en/US/tech/
+ tk648/tk361/technologies_tech_ note09186a0080094c32.shtml</a></font></p>
+
+ <p>
+ <IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE>
+ </TD>
+ </TR>
+ </TABLE><p>
+
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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