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1GbE Uplinks and stacking on Flex 10 to get ready for 10Gb

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1GbE Uplinks and stacking on Flex 10 to get ready for 10Gb

Dave has a customer that wants to prepare his network environment for 10GbE:



I was wondering for a customer that doesn't have 10GbE available.


Say they have an single enclosure full of BL460G6s...and Flex10 modules in 1 and 2. They want the NIC count and the future path to 10GbE.


They would put (8) 1GbE RJ45 SFPs in each Flex 10 module for now since they only have 1GbE on their switches, for a total of (16) possible uplinks.


They are worried about oversubsciption, and I suggested throttling down the speed on all the flex NICs to 1GbE or less.


They wondered if they could add additional 1/10 fiber VC modules in the enclosure, stack them to the Flex 10 modules with cables, and gain additional 1GbE uplinks.


This looks possible to me, but wanted to bounce it off the experts.


Cullen stepped in to advise:


I wouldn’t use 8 because that eliminates your cross links between bay 1 and 2.  The maximum 1 Gb uplinks you’d use would be 7.


Oversubscription is a fact of life in this setup.  Setting FlexNIC speeds is a good way to minimize that, but even if you had only 1Gb NICs you’d have 16/7 oversubscription.


Dave responded:


Thanks for the 7vs8 thing...I did not know that!


Question really is am I correct that the addition of (2) more 1/10 F VC modules in the stack would  give them 8 more usable 1GbE uplinks? We were not planning on adding any mezzanine cards only the embedded flex NICs.


Cullen's reply:




It would, though you couldn’t put them all in the same shared uplink set and expect to get more than ¼ of them up any one time.


Actually, you could get another 6 ports per module if you added 2x1Gb SFP modules in ports S1 and S2.  You would want to run a CX4 stacking link between these modules and the ones in bays 1 and 2.  This would cost you another uplink from the Flex10 modules, because the CX4 port shares the same hardware as X1.  You’d have a maximum of 6 x 1Gb ports per module, or 24 total ports.



Good info. Are you "future-profing" your network environment? What are you doing to make sure you are ready for 10Gb? We would love to hear your story.