Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 204)

The following example sets the port speed to 4 Gbps.
switch# configure terminal
Entering configuration mode terminal
switch(config)# interface FibreChannel 8/0/1
switch(config-FibreChannel-8/0/1)# speed 4
Configuring Fibre Channel ports for long-distance operation
Configuring a port for long-distance operation reserves the appropriate number of full-size frame
buffers for various long-distance modes. Be sure to observe preconditions for long distance operation
as outlined in this section.
Long-distance operation overview
Use the interface FibreChannel long-distance command to support long-distance links and to
allocate enough full-size frame buffers on a specific port. Changes made by this command are
persistent across switch reboots and power cycles.
This command supports the following long-distance link modes:
• Normal 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 operating
speed. The maximum supported link distance is up to 5 km at 2 Gbps, up to 2 km at 4 Gbps, and up
to 1 km at 8 Gbps.
• Extended mode (LE) — LE configures an E_Port distance greater than 5 km and up to 10 km. The
baseline for the calculation is one credit per km at 2 Gbps, which 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 Long-Distance mode (LD) — LD calculates buffer-to-buffer (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 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 (by means of the
desire-distance command). Network OS confines user entries to no larger than what it has
estimated the distance to be. When the measured distance is more than the specified desired
distance, the specified 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 set using the desire-distance command. LS also assumes that
all Fibre Channel payloads are 2,112 bytes. Specify LS to configure a static long-distance link with a
fixed buffer allocation greater than 10 km. Up to a total of 1,452 full-size frame buffers are reserved
for data traffic, depending on the specified desired-distance value.
Preconditions for long-distance operation
Before configuring an extended ISL, ensure that the ports on both ends of the ISL are operating at the
same port speed and can be configured at the same distance level without compromising local switch
performance.
Only qualified Brocade SFP transceivers are used. Only Brocade-branded or certain Brocade-qualified
SFPs are supported.
Configuring Fibre Channel ports for long-distance operation
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