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<a name="wp1092910"> </a><h1 class="pTitle">
Target Discovery

</h1>
<a name="wp1092912"> </a><p class="pBody">
iSCSI initiators discover targets by issuing queries to the iSNS server. The server supports <span style="font-style: italic">DevGetNext</span> 
requests to search the list of targets and <span style="font-style: italic">DevAttrQuery</span> to determine target and portal details, such as the 
IP address or port number to which to connect.

</p>
<a name="wp1092913"> </a><p class="pBody">
On receiving a query request from the iSCSI client, the iSNS server queries the Fibre Channel Name 
Server (FCNS) to obtain a list of Fibre Channel targets that are accessible by the querying initiator. The 
result of this query depends on zoning configuration currently active and current configuration(s) of the 
initiator. The iSNS server will subsequently use the iSCSI target configuration(s) (virtual target and 
dynamic import configuration) to translate the Fibre Channel target to an equivalent iSCSI target. At this 
stage it also applies any access control configured for the virtual target. A response message with the 
target details is then sent back to the query initiator. 

</p>
<a name="wp1092914"> </a><p class="pBody">
The iSNS server sends a consolidated response containing all possible targets and portals to the querying 
initiator. For example, if a Fibre Channel target is exported as different iSCSI targets on different IPS 
interfaces, the iSNS server will respond with a list of all possible iSCSI targets and portals. 

</p>
<a name="wp1092915"> </a><p class="pBody">
In order to keep the list of targets updated, the iSNS server sends state change notifications (SCN) to the 
client whenever an iSCSI target becomes reachable or unreachable. The client is then expected to 
rediscover its list of accessible targets by initiating another iSNS query. Reachability of iSCSI targets 
changes when any one of the following occurs:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1092916"> </a><li class="pSmartList1">Target goes up or down.
</li>
<a name="wp1092917"> </a><li class="pSmartList1">Dynamic import of FC target configuration changes.
</li>
<a name="wp1092918"> </a><li class="pSmartList1">Zone set changes.
</li>
<a name="wp1092919"> </a><li class="pSmartList1">Default zone access control changes.
</li>
<a name="wp1092920"> </a><li class="pSmartList1">IPS interface state changes.
</li>
<a name="wp1092923"> </a><li class="pSmartList1">Initiator configuration change makes the target accessible or inaccessible.
</li>
</ul></div>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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