Reference Guide

Formula for Gen-5 16-Gbps and older devices
The remaining buffers = (Total FE Ports * 8) + (Total BE/BI Ports * Buffers for BE/BI Port) + EMB Buffers + SAB Buffers
TABLE 18 Configurable distances for Extended Fabrics
Maximum distances (km) that can be configured (assuming a 2112-byte frame size)
Switch/blade model 2 Gbps 4 Gbps 8 Gbps 10 Gbps 16 Gbps
M6505 N/A 3949 1974 N/A 987
6505 7898 3949 1974 N/A 987
6510 7706 3853 1926 1541 963
6520 4778 2389 1194 955 597
6542 N/A 3853 1926 N/A 963
6543 N/A 3949 1974 N/A 987
6545 N/A 3941 1970 N/A 985
6546 N/A 3949 1974 N/A 987
6547 N/A 3853 1926 N/A 963
6548 N/A 3933 1966 N/A 983
6549 N/A 3949 1974 N/A 987
6558 N/A 3853 1926 N/A 963
6559 N/A 3853 1926 N/A 963
7840 5018 2509 1254 1003 627
FC16-32 5402/2458 2701/1229 1350/614 1080/491 675/307
FC16-48 4954/2010 2477/1005 1238/502 990/402 619/251
FC16-64 4282/1338 2141/669 1070/334 856/267 535/167
*** Extended Fabrics is not recommended on this blade due to buffer limitations but can be configured. ***
FX8-24 982 491 245 N/A N/A
NOTE
The distances in the above table assume that QoS is enabled. If QoS is disabled, the maximum supported distances are higher,
because QoS requires an additional 20 buffer credits per active port.
Estimated maximum equally distributed distance = 1-port maximum distance/Number of ports
NOTE
For the FC16-x port blades, the first number in the speed column designates the distance (km) supported at that speed without
buffer optimized mode; the second number designates the distance (km) supported at that speed with buffer optimized mode
enabled on the slot. Use the bufOpMode command to display or change the buffer optimized mode
For example, for three ports running at 2 Gbps on a Brocade 6505 switch, the maximum equally distributed distance is calculated as
7898 / 3 = 2633 km.
Downgrade considerations
NOTE
The downgrade from Fabric OS 7.3.0 to 7.2.0 or 7.1.0 is not affected by the conditions discussed in this section. These
conditions are applicable only for downgrading from Fabric OS 7.1.0 to an earlier verison.
Buffer-to-Buffer Credits and Credit Recovery
Brocade Fabric OS Administration Guide, 8.0.1
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