Limitations and Restrictions
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 .
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MTU Size Limitation
The Cisco MDS 9216i switch and MPS-14/2 module do not support an MTU size greater than 8000
bytes. An attempt to set the MTU size greater than 8000 bytes will result in an error. As a workaround,
reset the value of the MTU size (576 to 8000 bytes) and issue the no shutdown command on the interface
for normal operation.
Reconfiguring SSM Ports
Starting with Cisco MDS SAN-OS Release 3.0(1), the SSM front panel ports can no longer be configured
in auto mode, which is the default for releases prior to Release 3.1(1). For instructions about how to
modify the configuration of the ports before upgrading to SAN-OS Release 3.1(3), see the
"Reconfiguring SSM Ports Before Upgrading to SAN-OS Release 3.1(3)" section on page
Virtual Router Redundancy Protocol (VRRP) Interfaces
When a switchover occurs on a switch that is the master for Virtual Router Redundancy Protocol (VRRP)
interfaces, the switchover may cause a minor delay. As a result, the VRRP backup (occurring elsewhere)
may assume the role of the VRRP master. As a workaround, increase the VRRP advertisement interval
for these interfaces.
QoS on an MDS 48-port Fibre Channel Module
Due to possible differences in parts per million between the MAC ASICs on both sides of an ISL link,
there is a potential throughput issue when running QoS over an ISL on an MDS 48-port Fibre Channel
module. Specifically, the user may not see traffic throughput that follows the programmed QoS ratios.
The throughput ratio on the high and/or medium priority class of service (COS) relative to the low
priority COS, may not be as high as the actual programmed ratio.
If this situation occurs, you can move the ISL to a port on a different port group on one and/or both sides
of the link, or move the ISL to a port on a lower-density card if you require accurate QoS ratios.
Cisco MDS 9000 Family Release Notes for Cisco MDS SAN-OS Release 3.1(3)
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The iSNS feature does not support a graceful downgrade from Cisco MDS SAN-OS Release 3.1(3)
to any earlier SAN-OS release. Prior to a downgrade from Cisco SAN-OS 3.1(3), disable the MDS
iSNS server and remove all configurations associated with the MDS iSNS client.
The Cisco MDS 9000 switches iSNS server does not support registration, query, or state change
information from an actual iSCSI target.
The iSNS client registers all targets outside the permitted VSAN if you configure the iSCSI interface
and targets to be part of different VSANs.
The iSNS client functionality on Cisco MDS 9000 switches does not work on VRRP interfaces.
The iSNS client functionality on Cisco MDS 9000 switches does not support registration of iSLB
initiators.
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OL-12208-05
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