Pinned topic Nexus and Fibre Channel Issue with AIX
**This issue with AIX HBA has been reported to have port initialization failure issue with the Nexus switches.**
**An AIX host cannot connect via FC HBA to a N55xxUP FC port.**
**As you mentioned this is fixed by forcing the HBA to bypass the “initialization” algorithm during negotiation to prevent the timing issue.**
AIX server that is either Fibre Channel or FCoE attached to an N5K. AIX is the only device that uses Class 2 for its Fibre Channel Control Plane Traffic. (FICON does as well, but the N5K does not support FICON).
This works when the port mode is hard coded to “F” or “FX” on the switch side in combination with the changes on the AIX HBA recommended as follows:
To make the AIX host use Class 3 and point to point (instead of AL)
# chdev -l fcs0 -a sw_fc_class=3 -P
# chdev -l fcs0 -a init_link=pt2pt -P
Both are required for successful operation.
Replace fcs0 with the appropriate HBA identifier
This is not a switch issue and there are no other configurable parameters in the switch to circumvent this issue.
Please involve the AIX hba vendor/development to address this issue.
From the Cisco remark it appears there are issues with the IBM HBA's, we want to move our dual VIO NPIV production environment to the new switches but we are sort of hesitant, has anyone else moved to these switches and have you heard or seen these type of issues with the 8gb cards?
MatthewBourne 1100004XY11 Post
Re: Nexus and Fibre Channel Issue with AIX2013-06-24T18:47:58ZThis is the accepted answer. This is the accepted answer.
What's the FC code of your HBA, and what model of 770 is it? What version of VIOS?
This might help you work out whether you're looking at an unsupported configuration, from an IBM perspective:
I tried a couple of combinations, but I couldn't see a supported mix that included 770, 8 Gbit HBA, and Cisco Nexus :(
deesk 060000NDSK2 Posts
Steve Parker 2700045EYV1 Post
Re: Nexus and Fibre Channel Issue with AIX2014-05-01T18:39:09ZThis is the accepted answer. This is the accepted answer.
- deesk 060000NDSK
Just about a year later....deesk, did you ever get a clear direction on your issue?
We also have multiple P770-MMB with FC5735 HBA's and are now planning moving to Cisco Nexus 5596. Looking for any info possible.
timmymic 270007P7FP1 Post
Re: Nexus and Fibre Channel Issue with AIX2015-03-24T21:08:07ZThis is the accepted answer. This is the accepted answer.
I am having the same issue with a P5 550 connecting to the Nexus 5596 UP. I used the commands given above and still receiving error that I am sending class 2. Has anyone figured this out yet?
midnightengr 10000016QN1 Post
Re: Nexus and Fibre Channel Issue with AIX2017-05-24T05:36:18ZThis is the accepted answer. This is the accepted answer.
- timmymic 270007P7FP
Yes - from Cisco Support Engineer, "... it looks like the FC2 process on the N5K is throttling the number of reject frames sent so we are seeing FC2 drops. FC2 uses a throttling process to protect the CPU of the switch. The N5K has to reject every class 2 request as it's not supported. Once the switch sends 20 reject frames, if there are more of them to be sent within the same 100ms time interval the switch starts dropping them until the next 100ms interval"
This resulted in not being able to discover all paths, and in some cases with over 100 LUNs, some LUNs weren't discoverable either. To make matters worse, sometimes, previously working paths would go into a dead/defined state after scanning the fcsX buses. After spending several months, and a lot of resources, IBM branded Brocades switches were put in place and have been working great since.