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Chapter 35
Configuring iSCSI
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
To configure the ESI retry count for an iSNS server, follow these steps:
Command
Step 1
switch# config t
switch(config)#
Step 2
switch(config)# isns esi retries 6
switch(config)# no isns esi
retries 6
iSNS Client Registration and Deregistration
An iSNS client cannot query the iSNS server until it has registered. You can use the show isns database
command to display all registered iSNS clients and their associated configuration.
iSNS client deregistration can occur either explicitly or when the iSNS server detects that it can no
longer reach the client (through ESI monitoring).
iSNS client registration and deregistration result in status change notifications (SCNs) being generated
to all interested iSNS clients.
Target Discovery
iSCSI initiators discover targets by issuing queries to the iSNS server. The server supports DevGetNext
requests to search the list of targets and DevAttrQuery to determine target and portal details, such as the
IP address or port number to which to connect.
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.
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.
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:
1.
2.
3.
4.
5.
6.
OL-6973-03, Cisco MDS SAN-OS Release 2.x
Target goes up or down
Dynamic import of FC target configuration changes
Zone set changes
Default zone access control changes
IPS interface state changes
Initiator configuration that change make the target accessible or inaccessible.
Purpose
Enters configuration mode.
Configures the ESI to retry contacting the client up to 6 times.
The range is 1 to 10.
Reverts to the default value of 3 retries.
Cisco MDS 9000 Family Configuration Guide
Configuring iSNS Servers
35-65
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