Technical data
Fabric OS Administrator’s Guide 11-1
Publication Number: 53-0000518-09
Chapter
11
Administering Extended Fabrics
This chapter contains procedures for using the Brocade Extended Fabrics licensed feature, which
extends the distance that interswitch links (ISLs) can reach. To use extended ISL modes, you must first
install the Extended Fabrics license. For details on obtaining and installing licensed features, refer to
“Maintaining Licensed Features” on page 2-8.
About Extended Link Buffer Allocation
As the distance between switches and the link speed increase, additional buffer-to-buffer credits are
required to maintain maximum performance. The number of credits reserved for a port depends on the
switch model and on the extended ISL mode for which it is configured.
SilkWorm 3016, 3250, 3850, 3900, 12000, 24000,
and 48000 (FC2-16 Port Blades)
For the SilkWorm 3016, 3250, 3850, 3900, 12000, 24000, and 48000 using FC2-16 port blades, each
port group contains four ports and uses a common pool of credits. Because the number of credits
available for use within each port group is limited, configuring ports for extended links on these models
might cause other ports to become disabled if there are not enough buffer credits available; for example:
• If two 2-Gbit/second ports in a group are configured for L1 mode, each will be allocated enough
buffer-to-buffer credits to cause the other two ports in the group to become disabled.
• A port connected to a device that is in loopback mode might become disabled for lack of buffers if
another port in that group is set to L2 mode.
Refer to Chapter 5, “Configuring SilkWorm 12000, 24000, and 48000 Directors” for details about port
blade nomenclature.
SilkWorm 4012, 4100, and 48000 (FC4-16 and
FC4-32 Port Blades)
For the SilkWorm 4100 and 48000 director using FC4-16 and FC4-32 port blades, buffer credits are
used by all ports on chip. Buffer-limited port technology allows all ports to remain operational, even
when extended links are in use.
For the SilkWorm 4012, buffer credits are available to all ports on the chip.