two or more chassis with clustered fabric interconnect

Answered Question
Mar 17th, 2010
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Hi experts


Just wanna confirm the proper way to connect two or more UCS 5108 chassis with a pair of clustered 6120xp fabric interconnect.


I though they should connect like this: the first fabric extender of all chassis should connect to fabric interconnect A, and second fabric extender of all chassis connects to fabric interconnect B. like in the diagram here:  https://supportforums.cisco.com/docs/DOC-5949


however I have seen someone did this: chassis 1 connects as I though above, but for chassis 2, fabric extender 1 connecting to fabric interconnect B, and fabric extender 2 connecting fabric interconnect A - crossed over.


can someone tell me which is appropiate/best practice? any reason why crossing over on the second chassis??


thanks

ming

Correct Answer by Anonymous about 7 years 4 months ago

ming, you need to fix that implementation.  it's like ghostbusters: don't cross the streams!


Always consistently cable chassis fex to the same fabric interconnect.  Most common setup:


Fabric Interconnect A (Primary) is connected to all Left Hand (looking from back of chassis) FEX


Fabric Interconnect B (Subordinate) is connected to all Right Hand FEX.


Why?  You will get errors (can't be bothered looking them up!) and if you move a Service Profile from one chassis to another chassis that is cabled differently, then it won't work (CNAs cabled to different FIs where VIFs are active / inactive = bad).


PS - to change this, if I was you, I would power down the whole system - fabric interconnects, chassis, everything.  then re-cable.  then power up the fabric interconnects and chassis and check the configurations are ok. 

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Correct Answer
stechamb Wed, 03/17/2010 - 08:22
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ming, you need to fix that implementation.  it's like ghostbusters: don't cross the streams!


Always consistently cable chassis fex to the same fabric interconnect.  Most common setup:


Fabric Interconnect A (Primary) is connected to all Left Hand (looking from back of chassis) FEX


Fabric Interconnect B (Subordinate) is connected to all Right Hand FEX.


Why?  You will get errors (can't be bothered looking them up!) and if you move a Service Profile from one chassis to another chassis that is cabled differently, then it won't work (CNAs cabled to different FIs where VIFs are active / inactive = bad).


PS - to change this, if I was you, I would power down the whole system - fabric interconnects, chassis, everything.  then re-cable.  then power up the fabric interconnects and chassis and check the configurations are ok. 

minghui.qi Thu, 03/18/2010 - 06:31
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Hi Steve,


thanks for your reply, I will get it fixed:


could you plealse explain a bit more on "it won't work (CNAs cabled to different FIs where VIFs are active / inactive = bad).", just wanna be clear on the real impact.. or please point me to a link or doc, I can't find such confiugration on standard Cisco Nexus 1000 v docs.


thank you

ming

minghui.qi Wed, 03/24/2010 - 07:32
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Thanks, Nethaji.. I have already got that doc. but I can't find it mentioning about two more more chassis connectivity, maybe I missed it?

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