Fibre Channel (SAN)

Posts: 1
Registered: ‎02-21-2013

8gb ports and fillword

I have Brocade DCX directors and all of the ports have the fillword set to 0.  Should I go ahead and set all ports fillword to 3.  As we move forward we are adding more and more 8gb devices and none of them are fillword 3.  Is there a downside to settings all ports to fillword 3?  Will 2gb or 4gb devices still work with the fillword set to 3?



Frequent Contributor
Posts: 160
Registered: ‎08-07-2009

Re: 8gb ports and fillword

Below is a little background on Fabric OS (FOS) link initialization and fill word primitive configuration for Brocade

8G Fibre Channel platforms. By providing the flexibility to choose primitives for link initialization and fill word

configuration, Brocade ensures full interoperability with all 8G capable FC HBAs and storage devices.

Up through the FOS v6.1.1 release, Brocade Fibre Channel switches used IDLE primitives both during link

initialization and for fill words (denoted as “IDLE/IDLE”). This ensured successful link initialization between

Brocade switch ports and end devices operating at 1G/2G/4G speeds.

With the introduction of 8G Fibre Channel, FC-PI-4 and FC-FS-3 standards stated that ARB should be used as

fill words for lowering emission. To comply with the published FC standards, Brocade introduced options for

ARB/ARB and IDLE/ARB link initialization/fill word support.

However, some 8G devices are not capable of properly establishing links with Brocade 8G Fibre Channel

switches when ARB/ARB or IDLE/ARB primitives are used. These 8G devices require the legacy IDLE/IDLE

sequence to achieve successful link initialization. To address this issue, Brocade has provided the ability to

configure any of the three possible combinations (IDLE/IDLE, ARB/ARB, or IDLE/ARB) for link initialization and

fill words. Any of these modes can be configured on an individual port basis using the CLI portcfgfillword. This

CLI also provides an option to automatically switch from ARB/ARB to IDLE/ARB if the former is not able to

successfully establish a link. (Please see the CLI documentation in the Appendix or in the FOS Command

Reference Manual for further details). This capability is available in FOS v6.3.1 and later versions of firmware.

In summary, FOS v6.3.1 and later versions support the following modes for 8G F_Ports as a per port


MODE           MEANING

Mode 0      Use IDLE in link init and IDLE as fill word

Mode 1      Use ARB in link init and ARB as fill word

Mode 2      Use IDLE in link init and ARB as fill word

Mode3       Try mode 1 first; if it fails then try mode 2

Join the Community

Get quick and easy access to valuable resource designed to help you manage your Brocade Network.