442 Fabric OS Administrator’s Guide
53-1001763-02
Extended Fabrics device limitations
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Extended Fabrics device limitations

Extended Fabrics is normally not implemented on the following devices:
•7600 and the FA4-18 blade - The 7600 and the FA4-18 blade have two Gigabit Ethernet ports
and 16 FC ports. The two Gigabit Ethernet ports are for use by storage applications, and
generally the FC ports on these devices are used to connect devices used by the storage
applications.
•FC4-16IP blade - The FC4-16IP blade has eight Gigabit Ethernet ports and eight FC ports. It is
used to implement the iSCSI Gateway Service. The Gigabit Ethernet ports are used to connect
iSCSI initiators, and the FC ports are used to connect to any device.
•FC8-64 blade - Extended Fabrics is not supported on this blade.
•Brocade 8000 - Extended Fabrics is not supported on this platform.

Long distance link modes

Use the portCfgLongDistance command to support long distance links and to allocate sufficient
numbers of full size frame buffers on a particular port. Changes made by this command are
persistent across switch reboots and power cycles. This command supports the following
long-distance link modes:
•Static Mode (LO) - L0 is the normal (default) mode for a port. It configures the port as a regular
port. A total of 20 full-size frame buffers are reserved for data traffic, regardless of the port’s
operating speed; therefore, the maximum supported link distance is up to 10 km at 1 Gbps, up
to 5 km at 2 Gbps, up to 2 km at 4 Gbps, and up to 1 km at 8 Gbps.
•Static Mode (LE) - LE configures an E_Ports distance greater than 5 km and up to 10 km. LE
does not require an Extended Fabrics license. The baseline for the calculation is one credit per
km at 2 Gbps. This yields the following values for 10 km:
-5 credits per port at 1 Gbps.
-10 credits per port at 2 Gbps.
-20 credits per port at 4 Gbps.
-40 credits per port at 8 Gbps.
•Dynamic Mode (LD) - LD calculates BB credits based on the distance measured during port
initialization. Brocade switches use a proprietary algorithm to estimate distance across an ISL.
The estimated distance is used to determine the BB credits required in LD (Dynamic) extended
link mode based on a maximum Fibre Channel payload size of 2,112. You can place an upper
limit on the calculation by providing a desired_distance value. Fabric OS confines user entries
to no larger than what it has estimated the distance to be. When the measured distance is
more than desired_distance, the desired_distance (the smaller value) is used in the
calculation.
•Static Long-Distance Mode (LS) - LS calculates a static number of BB credits based only on a
user-defined desired_distance value. LS mode also assumes that all FC payloads are 2112
bytes. Specify LS mode to configure a static long distance link with a fixed buffer allocation
greater than 10 km. Up to a total of 1452 full-size frame buffers are reserved for data traffic,
depending on the specified desired_distance value.
NOTE
Long distance modes L0.5, L1, and L2 are not supported on Fabric OS v6.x.