How to prevent VSAN0001 segmentation

Answered Question
Sep 20th, 2010

Hello guys,


When i connect a new switch to my fabric, i always see VSAN0001 segments. We are not using VSAN001 for anything, its state is down ..it does not really affect anything but i just hate to see it listed like that. Other than setting "trunk allow" vsan 1 ..anything else i can do ?


vsan0001_segments.jpg

Correct Answer by bfeeny about 6 years 5 months ago

Yes, I believe so, if not right away, then the next time that port is shut/no shut, so not a good idea.  You cannot suspend the Port VSAN of a TE port without it taking down the port basically.  So you can only trunk your Transit VSAN that's fine, but whatever you use as the port VSAN  you need to keep as an active VSAN, not suspended. 


Brian

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bfeeny Mon, 09/20/2010 - 19:31

I don't believe there is anything you can do here, it is the expected/normal behavior, as even though it is down, it is in fact segmented.  Like you, I typically don't use VSAN1.  There may be something in FM you can do to "Hide suspended VSAN's" or something, I am not sure.


Brian

Steven.langdale_2 Mon, 09/20/2010 - 22:51

Hello


On the 1st Cisco SAN course I went on 2-3 years back, the instructer told us it was good practice to always trunk vsan 1.


I can't remeber why to be honest!  And no, I don't use it for anything either.


At least you get a nice clean screen in FM.


Steven

bfeeny Tue, 09/21/2010 - 05:40

There is no reason to trunk VSAN1 or any VSAN for that matter unless its actually being used. 


There are some bugs out there where you need to trunk the Port VSAN, however I would not even do this unless you are hitting those bugs.  For example, say the Port VSAN for fc1/1 (TE Port) is 2, so then you may need to trunk VSAN 2 to avoid certain bugs.  But this is a bug issue, not a design issue.


VSAN1 is bad because its the default port VSAN.  Not using VSAN1 is a good practice as this way if someone plugs in a switch and it starts to trunk, you are not introducing fabric instability and other undesired behavior. 


I am pretty sure older FM's did not show the VSAN001's as segmented, (3.3), I believe later on this showed this way, and that's why I thought maybe there is a preference option to display it this way, or it may just be the changed behavior of FM.


Brian

dynamoxxx Tue, 09/21/2010 - 06:42

i just tried something.  I suspended VSAN 1 on both switches and now segmentation is gone. Right now i am playing with two test servers but in the future my DWDM ports will be in VSAN 1, so i wonder if suspending VSAN 1 would case any harm.


bfeeny Tue, 09/21/2010 - 07:42

You can't suspend the Port VSAN of a TE port without causing issues.  So, whatever VSAN you use for your Port VSAN, will show segmented unless you trunk it.  You can suspend VSAN1 and leave it that way, and just not put anything in it.  But if you are going to use it for Port VSAN's then you will need to leave it active. You don't have to trunk it but it can't be suspended.


Brian

dynamoxxx Tue, 09/21/2010 - 11:02

Brian,


if you remember from my previous discussion about IVR and transit VSANs,  i will place my long-wave ports that provide DWDM connectivity into VSAN 1 and the only VSAN that will be allowed to trunked will be my transit VSAN  ...so if i suspend VSAN 1 that essentially will take that port offline and break my DWDM link ?

Correct Answer
bfeeny Tue, 09/21/2010 - 11:40

Yes, I believe so, if not right away, then the next time that port is shut/no shut, so not a good idea.  You cannot suspend the Port VSAN of a TE port without it taking down the port basically.  So you can only trunk your Transit VSAN that's fine, but whatever you use as the port VSAN  you need to keep as an active VSAN, not suspended. 


Brian

dynamoxxx Tue, 09/21/2010 - 13:58

you are absolutely right. I just tested this by moving TE port on each switch to a suspended VSAN 1, at first the link between the two switches was up but as soon as i "shut/no shut" the port ..link status went to "inactive" and connectivity between the two stopped. I guess i'll just live with "segmented" VSAN 1.


Thank you so much Brian

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