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    <title>Extended BB_credits on Generation 1 Switching Modules </title>
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<a name="wp1073742"> </a><h1 class="pTitle">
Extended BB_credits on Generation 1 Switching Modules

</h1>
<a name="wp1073743"> </a><p class="pBody">
The BB_credits feature allows you to configure up to 255 receive buffers on Generation 1 switching 
modules. To facilitate BB_credits for long haul links, you can configure up to 3,500 receive BB_credits 
on a Fibre Channel port on a Generation 1 switching module.

</p>
<a name="wp1073744"> </a><p class="pBody">
To use this feature on Generation 1 switching modules, you must meet the following requirements:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1073746"> </a><li class="pSmartList1">Obtain the ENTERPRISE_PKG license. See the <em class="cEmphasis">Cisco MDS 9000 Family NX-OS Licensing Guide</em>.
</li>
<a name="wp1073749"> </a><li class="pSmartList1">Configure this feature in any port of the full-rate 4-port group in either the Cisco MDS 9216i Switch 
or in the MPS-14/2 module . 
</li>
<a name="wp1073760"> </a><p class="pListBodyLevel1">
The port groups that support extended credit configurations are as follows:

</p>
<div class="pSmartList2"><ul class="pSmartList2">
<a name="wp1073761"> </a><li class="pSmartList2">Any one port in ports 1 to 4 (identified as Group 1). </li>
<a name="wp1073762"> </a><li class="pSmartList2">Any one port in ports 5 to 8 (identified as Group 2).</li>
<a name="wp1073763"> </a><li class="pSmartList2">Any one port in ports 9 to 12 (identified as Group 3).</li>
<a name="wp1073764"> </a><p class="pBodyAutonumRel">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The last two Fibre Channel ports (port 13 and port 14) and the two Gigabit Ethernet ports 
do not support the extended BB_credits feature.

</p>
</ul></div>
<a name="wp1073765"> </a><li class="pSmartList1">Explicitly enable this feature in the required Cisco MDS switch.
</li>
<a name="wp1073766"> </a><li class="pSmartList1">Disable the remaining three ports in the 4-port group if you need to assign more than 2,400 
BB_credits to the first port in the port group.
</li>
<div class="pSmartList2"><ul class="pSmartList2">
<a name="wp1073767"> </a><li class="pSmartList2">If you assign less than 2,400 extended BB_credits to any one port in a port group, the remaining three ports in that port group can retain up to 255 BB_credits based on the port mode. </li>
<a name="wp1073768"> </a><p class="pBodyAutonumRel">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The receive BB_credit value for the remaining three ports depends on the port mode. 
The default value is 16 for the Fx mode and 255 for E or TE modes. The maximum value 
is 255 in all modes. This value can be changed as required without exceeding the 
maximum value of 255 BB_credits.

</p>
<a name="wp1073769"> </a><li class="pSmartList2">If you assign more than 2,400 (up to a maximum of 3,500) extended BB_credits to the port in a port group, you must disable the other three ports. </li>
</ul></div>
<a name="wp1073770"> </a><li class="pSmartList1">If you change the BB_credit value the port is disabled, and then reenabled.
</li>
<div class="pSmartList2"><ul class="pSmartList2">
<a name="wp1073771"> </a><li class="pSmartList2">Disable (explicitly) this feature if you need to nondisruptively downgrade to Cisco SAN-OS Release 1.3 or earlier. When you disable this feature, the existing extended BB_credit configuration is completely erased. </li>
</ul></div>
</ul></div>
<a name="wp1073772"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> The extended BB_credit configuration takes precedence over the receive BB_credit and performance 
buffer configurations.

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

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