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<td bgcolor="#336666"><font face="Arial" size="2" color="#FFFFFF"><b>4.</b></font><b><font face="Arial" size="2" color="#FFFFFF">3</font></b></td>
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<td bgcolor="#336666" width="100%"><b>
<font face="Arial" size="2" color="#FFFFFF">DDR Configuration</font></b></td>
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<td bgcolor="#669999" height="25"><b>
<font face="Arial" size="2" color="#FFFFFF">4.3.9</font></b></td>
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<td bgcolor="#669999" height="25" width="100%"><strong>
<font face="Arial" size="2" color="#FFFFFF">Troubleshooting the DDR
configuration</font></strong></td>
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<td><font face="Arial" size="2">There are two major types of DDR
problems. Either a router is not dialing when it should, or it is
constantly dialing when it should not. Several </font>
<font face="Courier New" size="2"><b>debug</b></font><font face="Arial" size="2">
commands can be used to help troubleshoot problems with a DDR
configuration.</font><p><font face="Arial" size="2">The </font>
<font size="2" face="Courier New"><b>debug isdn q921</b></font><font face="Arial" size="2">
command is useful for viewing Layer 2 ISDN call setup exchanges.
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> The �i =�
field in the Q.921 payload field is the hexadecimal value of a Q.931
message. In the following lines, the seventh and eighth most significant
hexadecimal numbers in the �i =� field indicate the type of Q.931
message: </font></p>
<ul>
<li><font face="Arial" size="2">0x05 indicates a call setup message
</font></li>
<li><font face="Arial" size="2">0x02 indicates a call proceeding
message </font></li>
<li><font face="Arial" size="2">0x07 indicates a call connect message
</font></li>
<li><font face="Arial" size="2">0x0F indicates a connect
acknowledgment (ack) message</font></li>
</ul>
<p><font face="Arial" size="2">The </font>
<font size="2" face="Courier New"><b>debug isdn q931</b></font><font face="Arial" size="2">
command is useful for observing call setup exchanges for both outgoing
and incoming calls.
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12">
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"></font></p>
<p><font face="Arial" size="2">The </font>
<font size="2" face="Courier New"><b>debug dialer [events | packets]</b></font><font face="Arial" size="2">
command is useful for troubleshooting DDR connectivity. The </font>
<font size="2" face="Courier New"><b>debug dialer events</b></font><font face="Arial" size="2">
command sends a message to the console indicating when a DDR link has
connected and what traffic caused it to connect.
<img border="0" src="../../images/4.gif" align="absmiddle" width="12" height="12"> If a router
is not configured correctly for DDR, then the output of the command will
usually indicate the source of the problem. If there is no debug output,
then the router is not aware of any interesting traffic. An incorrectly
configured dialer or access list may be the cause. </font></p>
<p><font face="Arial" size="2">Not all DDR problems result in an
interface failing to dial. Routing protocols can cause an interface to
continuously dial, even if there is no user data to send. An interface
that is constantly going up and down is said to be flapping. The </font>
<font size="2" face="Courier New"><b>debug dialer packet</b></font><font face="Arial" size="2">
command sends a message to the console every time a packet is sent out a
DDR interface. Use this debug command to see exactly what traffic is
responsible for a flapping DDR interface.</font></p>
<p><font face="Arial" size="2">If a router is not connecting when it
should, then it is possible that an ISDN problem is the cause, as
opposed to a DDR problem. The remote router may be incorrectly
configured, or there could be a problem with the ISDN carrier network.
Use the </font><font size="2" face="Courier New"><b>isdn call interface</b></font><font face="Arial" size="2">
command to force the local router to attempt to dial into the remote
router. <img border="0" src="../../images/5.gif" align="absmiddle" width="12" height="12"> If
the routers cannot communicate using this command, then the lack of
connectivity is an ISDN problem, not a DDR problem. However, if the
routers can communicate, then both the toll network and the ISDN
configurations on the routers are working properly. In this case, the
problem is most likely an error in the DDR configuration on either
router.</font></p>
<p><font face="Arial" size="2">In some cases it is useful to reset the
connection between the router and the local ISDN switch. The </font>
<font size="2" face="Courier New"><b>clear interface bri</b></font><font face="Arial" size="2">
command clears currently established connections on the interface and
resets the interface with the ISDN switch. This command forces the
router to renegotiate its SPIDs with the
ISDN switch, and is sometimes necessary after making changes to the
</font><font size="2" face="Courier New"><b>isdn spid1</b></font><font face="Arial" size="2">
and </font><font size="2" face="Courier New"><b>isdn spid2</b></font><font face="Arial" size="2">
commands on an interface.</font></p>
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<TD>
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<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/mod04/elab_4_3_9/elab4_3_9.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>
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</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>e-Lab Activity:
</font><font FACE="Courier New" SIZE="2" COLOR="#808080">
<b>isdn spid</b></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>In this activity, the student will demonstrate how to use the
</font><font FACE="Courier New" SIZE="2" COLOR="#808080">
<b>isdn spid </b></font><font FACE="Arial" SIZE="2" COLOR="#808080">
command to define at the router the service profiles identifier
number that was assigned by the ISDN service provided for the B1
channel.</p>
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<p><font color="#808080">
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<b>Web Links</b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>Tech Notes<p>
<a target="_blank" href="http://www.cisco.com/en/US/tech/tk801/tk133/tech_tech_notes_list.html">
http://www.cisco.com/en/US/tech/
tk801/tk133/ tech_tech_notes_ ist.html</a></font></p>
<p>
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