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Fibre Channel (SAN)

Occasional Contributor
Posts: 8
Registered: ‎07-28-2010

When Could I use ISL_R_RDY mode?

Hello all.


I connected between 2 Brocade 6510 with 4 ISL lines (8G LW SFP), I ran portcfgislmode 1 on ISL ports.

Threre are no DWDM or gateway between the switches, only Single cable.(Applox 700m)


Sometimes later, all the ISL line increased error counts (enc_in, CRC_err, CRC_W_geof).

So I remove the R_RDY mode on the ISL lines, there are no error counts increased.



So I have questions.


1. Could you explain how the ISL_R_RDY function works?


2. When could I use the ISL_R_RDY mode?


3. If I use ISL_R_RDY mode with out DWDM or gateway, why error counts increased?


Thanks all.


Frequent Contributor
Posts: 141
Registered: ‎05-26-2009

Re: When Could I use ISL_R_RDY mode?

ISL R_RDY mode is a costly compromise that is necessary with some range extenders for compatibility reasons. It has some significant disadvantages (for example that the VCs collapse and data traffic runs together with F-Class traffic, while the latter is prioritized).

So if you don't really need it (and based on your description you don't) then switch it off and use VC Link init instead. It's needed with active range extenders that can't process ARBs and VC specific ordered sets.


I don't see a direct connection between it and the physical errors you observed. It might be that the re-initialization of the link enhanced the signal a bit. If you see them again in the future next actions would be to clean the cable and (because LW SFPs come with a higher price tag) to check the SFPs with a wrap plug and the available tests in FOS.


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