UCS F port trunking and reserved VSAN confusion

Unanswered Question
Feb 15th, 2012

We have an existing UCS infrastructre where all  the FI's FC ports are connected to the MDS9513 as one to one connection ( no port channel or trunking) and the FI is working as "end host mode" . We are planning to move some crtical production application to the UCS infrastrcture and becuse of that we would like to use the FC port chanelling and F-port trunking. While reading some documents I found that there are some restriction on UCS for VSAN numbering while using the FI  for F-port trunking . As per the following doc http://www.cisco.com/en/US/docs/unified_computing/ucs/sw/cli/config/guide/2.0/b_UCSM_CLI_Configuration_Guide_2_0_chapter_010101.html#concept_5223F7F368524A39AB1A47B9F8BFEC8A

it says donot configure VSAN  ID range from 3840 to 4079 . The MDS 9513 is running NX-OS 4.2(3) . Our existing  MDS SAN infrstructure already  have 2 VSANs with ID number  4000 and 4001 ( Both of these VSANS are usied for some storage replication unrelated to UCS). In the UCS we alreay have 2 VSANS' ( 200 and 201) and are planning to create 2 more ( 300 and 301).  My question is if  I  configure the FI's  for  F-port truncking/FC port channeling then what will happen to my existing VSAN 4000 and 4001 on the MDS9513 SAN



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David McFarland Wed, 02/15/2012 - 13:27

There will be no effect to your MDS fabric. Also, as you are not using those VSANs on the UCS, there will be no effect on the UCS either. However, the restricted range of VSANs is NX-OS wide and has been introduced in newer versions of MDS and N5K NX-OS code. You may run into issues on the MDS when you upgrade to newer versions of MDS NX-OS code.

It's best to start planning to move off VSANs in that range. If these are replication VSANs only, the conversion should not be too disruptive. Create the new replication VSANs ourside of the restricted range. Pre-populate and activate the new zones/zoneset in the new replication VSAN. Then make a vsan db change for the replication ports in the fabric.


rajeshadhikari Wed, 02/15/2012 - 14:57

Hi David

Thanks for the reply.  Another question related to the above , If I do the F-port trunking than how much data interruption I should expect or it can be done  without any interruption.



David McFarland Wed, 02/15/2012 - 15:20

If you are asking how long it will take to enable f-port trunk and how disruptive it will be? It's not lengthy, but, it will cause the link to stop passing traffic and cause SCSI retrys. Your server will know it happened. If your fc multipathing is operating properly there will be no outage.If there are any configuration issues, the link may be down for an extended period, further compounding this disruption in traffic.

You initially asked about two features, f-port trunk and f-port channel. These are seperate features and require different configuration changes. It's best to add one feature at a time, not both in the same configuration change. Each change will be disruptive.

Do one fabric at a time. Ensure the f-port trunk is fully functional before doing the f-port channel, making sure it is functional before starting work on the second fabric.If your multipathing is operating as it should, there will be no outage. If there is any doubt schedule an outage window.


rajeshadhikari Wed, 02/29/2012 - 13:12

Hi Dave

In your first reply you said the " restricted VSAN range are on NX-OS side and been introduced on the newer MDS and N5K NX-OS code". I was wondering if you have a pointer from where I can find the vesion of Nx-OS code and the model of MDS where these VSAN numbers are restricted/reserved.

I was reading the following doc, where it says NX-OS 4.X and above has the new range of reserved VSAN 


As we are already running MDS NX-OS 4.2, I just want  to make sure that these reseved VSAN wont be disabled when I do the F port trunking to UCS



r.sharafi Wed, 03/14/2012 - 02:44


I was wodering what is the reason that the VSAN ID range from 3840 to 4079 is now reserved. What is used for internally?




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