Port Administrative Speeds; Autosensing; Frame Encapsulation - Cisco MDS 9000 Series Configuration Manual

Port Administrative Speeds

A graceful shutdown ensures that no frames are lost when the interface is shutting down. When a shutdown
is triggered either by you or the Cisco NX-OS software, the switches connected to the shutdown link coordinate
with each other to ensure that all the frames in the ports are safely sent through the link before shutting down.
This enhancement reduces the chance of frame loss.
A graceful shutdown is not possible in the following situations:
• If you physically remove the port from the switch.
• If In-Order Delivery (IOD) is enabled. For more details about IOD, see
• If the Min_LS_interval interval is higher than 10 seconds. For information about Fabric Shortest Path
Note
This feature is triggered only if both the switches at either end of the E port interface are Cisco MDS switches
and are running Cisco SAN-OS Release 2.0(1b) or later, or Cisco MDS NX-OS Release 4.1(1a) or later.
Port Administrative Speeds
By default, the port administrative speed for an interface is automatically calculated by the switch.

Autosensing

Auto sensing speed is enabled on all 4-Gbps and 8-Gbps switching module interfaces by default. This
configuration enables the interfaces to operate at speeds of 1 Gbps, 2 Gbps, or 4 Gbps on 4-Gbps switching
modules, and 8 Gbps on 8-Gbps switching modules. When auto sensing is enabled for an interface operating
in dedicated rate mode, 4 Gbps of bandwidth is reserved even if the port negotiates at an operating speed of
1 Gbps or 2 Gbps.
To avoid wasting unused bandwidth on 48-port and 24-port 4-Gbps and 8-Gbps Fibre Channel switching
modules, you can specify that only 2 Gbps of required bandwidth be reserved, not the default of 4 Gbps or 8
Gbps. This feature shares the unused bandwidth within the port group, provided the bandwidth does not exceed
the rate limit configuration for the port. You can also use this feature for shared rate ports that are configured
for auto sensing.
Tip When migrating a host that supports up to 2-Gbps traffic (that is, not 4 Gbps with auto-sensing capabilities)
to the 4-Gbps switching modules, use auto sensing with a maximum bandwidth of 2 Gbps. When migrating
a host that supports up to 4-Gbps traffic (that is, not 8 Gbps with auto-sensing capabilities) to the 8-Gbps
switching modules, use auto sensing with a maximum bandwidth of 4 Gbps.

Frame Encapsulation

The switchport encap eisl command applies only to SD port interfaces. This command determines the frame
format for all the frames transmitted by the interface in SD port mode. If the encapsulation is set to EISL, all
outgoing frames are transmitted in the EISL frame format, regardless of the SPAN sources. For information
about encapsulation, see the
Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
24
Fabric Configuration Guide.
First (FSPF) global configuration, see
.
Cisco MDS 9000 Series NX-OS System Management Configuration
Cisco MDS 9000 Series NX-OS Fabric Configuration Guide
Configuring Interfaces
Cisco MDS 9000 Series NX-OS
Guide.