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diff --git a/Bachelor/CCNA4/en_CCNA4_v30/ch1/1_2_8/content.html b/Bachelor/CCNA4/en_CCNA4_v30/ch1/1_2_8/content.html new file mode 100644 index 0000000..3de56c7 --- /dev/null +++ b/Bachelor/CCNA4/en_CCNA4_v30/ch1/1_2_8/content.html @@ -0,0 +1,249 @@ +<html>
+
+<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>1.2</font></b></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">DHCP</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">
+ 1.2.8</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">DHCP relay </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">
+ DHCP clients use IP broadcasts to find the DHCP server on the segment.
+ What happens when the server and the client are not on the same
+ segment and are separated by a router? Routers do not forward these
+ broadcasts.</font><p>
+ <font FACE="Arial" SIZE="2">
+ DHCP is not the only critical service that uses broadcasts. Cisco
+ routers and other devices may use broadcasts to locate TFTP servers.
+ Some clients may need to broadcast to locate a TACACS server. A TACACS
+ server is a security server. Typically, in a complex hierarchical
+ network, clients reside on the same subnet as key servers. Such remote
+ clients will broadcast to locate these servers. However, routers, by
+ default, will not forward client broadcasts beyond their subnet.</font></p>
+ <p>
+ <font FACE="Arial" SIZE="2">
+ Because some clients are useless without services such as DHCP, one of
+ two choices must be implemented. The administrator will need to place
+ servers on all subnets or use the Cisco IOS helper address feature.
+ Running services such as DHCP or DNS on several computers creates
+ overhead and administrative difficulties making the first option
+ inefficient. When possible, administrators should use the </font>
+ <font FACE="Courier New" SIZE="2">
+ <b>ip helper-address</b></font><font FACE="Arial" SIZE="2">
+ command to relay broadcast requests for these key UDP services.</font></p>
+ <p>
+ <font FACE="Arial" SIZE="2">
+ By using the helper address feature, a router can be configured to
+ accept a broadcast request for a UDP service and then forward it as a
+ unicast to a specific IP address. By default, the </font>
+ <font FACE="Courier New" SIZE="2">
+ <b>ip helper-address</b></font><font FACE="Arial" SIZE="2">
+ command forwards the following eight UDP services:</font></p>
+ <ul>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ Time</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ TACACS</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ DNS</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ BOOTP/DHCP Server</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ BOOTP/DHCP Client</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ TFTP</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ NetBIOS Name Service</font></li>
+ <li>
+ <font FACE="Arial" SIZE="2">
+ NetBIOS datagram Service</font></li>
+ </ul>
+ <p>
+ <font FACE="Arial" SIZE="2">
+ In the particular case of DHCP, a client broadcasts a DHCPDISCOVER
+ packet on its local segment.
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> This
+ packet is picked up by the gateway. If a helper-address is configured,
+ the DHCP packet is forwarded to the specified address. Before
+ forwarding the packet, the router fills in the GIADDR field of the
+ packet with the IP address of the router for that segment. This
+ address will then be the gateway address for the DHCP client, when it
+ gets the IP address.
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></font></p>
+ <p>
+ <font FACE="Arial" SIZE="2">
+ The DHCP server receives the discover packet. The server uses the GIADDR field to index into the list of address pools, to find one
+ which has the gateway address set to the value in GIADDR. This pool is
+ then used to supply the client with its IP address.
+ <img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12">
+ <img border="0" src="../../images/4.gif" align="absmiddle" width="12" height="12"></font></p>
+ <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_2_8/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: Configuring DHCP Relay</p>
+ <p>In this lab, a router will be configured for Dynamic Host
+ Configuration Protocol (DHCP).</p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <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_2_8/elab1_2_8.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_2_8/elab1_2_8.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: Configuring DHCP Relay</p>
+ </font><font FACE="Arial" SIZE="2" COLOR="#000000">
+ <p><font color="#808080">In this lab, the student will configure a router for DHCP, add the ability for workstations to remotely obtain DHCP
+ addresses and dynamically assign addresses to the attached
+ hosts.</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>Configuring DHCP Relay, DHCP Server, and PAT<p>
+ <a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/product/access/acs_fix/750/cfgguide/700cgdhc.htm">
+ http://www.cisco.com/univercd/cc/td/
+ doc/product/ ccess/acs_fix/750/
+ cfgguide/700cgdhc.htm</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>
+
+ <font face="Arial" size="2"> </font>
+ </td>
+ </tr>
+ </table>
+
+</body>
+
+</html>
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