Switch Stack Uplink design

[mmmartin823]

Question regarding uplinks in a stack of access switches: If we have let's say 4 access switches that are data stacked, can we just have uplinks be on the one switch and that will connect up the core/distribution layer?  (Trying to save cost on network modules buying on every switch if we don't need them)

Is there any advantage to have network module for uplinks on every switch in the stack? TIA!

[cmarva]

it depends on your need for redundancy. If there is no requirement, then a single uplink would work. In most environments, this is not acceptable, so at least two of the switches in the stack would be uplinked to the core. 

but again, it depends on your requirements for redundancy.

[balaji.bandi]

If you have stack of 4 switches, for better resilaince, i would expect you connect to uplink Switch 1 and Switch 2

so if switch 1 or 2 fails you have other uplink working. if you calculate downtime vs cost, cost is cheaper depends on business model.

[Martin L]

yes, you can use 1 module and you can choose any switch but most people use Switch 1 and Switch 2 (each has 1 fiber link).

if you use 1 module and switch goes down, you will have to move it to working switch.

note: that those Fiber Optic modules might be hot-swapable as they are in 3850 for sure as I had several techs replacing them without powering off switch.

Recommended set up is Switch 1 and Switch 2 has fiber modules and each switch has 1 fiber link in Port channel configuration going to main distribution switches.

Regards, ML
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[Leo Laohoo]

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@mmmartin823 wrote:

can we just have uplinks be on the one switch and that will connect up the core/distribution layer?

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Of course this can be done, HOWEVER, there is no redundancy.  

NOTE:  Minimize the urge to put the network module in the stack master.

[Joseph W. Doherty]

As the other posters have noted, normally you use at least two uplinks, on different stack members (avoiding using the stack master [and backup stack master - if possible for latter or both], as noted by Leo). Since the stack provides redundancy, the dual uplinks (as noted by the others), takes advantage of the stack's redundancy.

Also. since a stack operates as a single device, you can Etherchannel your uplinks, not only providing fast fail-over redundancy, but, on average, 50% more uplink bandwidth.

BTW, to avoid the cost of uplink port module, you can use a copper "edge" port for an uplink too.

[Deepak Kumar]

Hi,

you will face overutilization of the uplink port (if you have a single ten or gig port for all gig downside ports) and if that single uplink port will fail or switch fail than you have to manually switch the uplink cable on working switch and you can calculate the cost of that downtime. 

As everyone mentioned that don't use the uplink cable on the master switch for some technical reason (don't want to describe here). 

[Joseph W. Doherty]

"you will face overutilization of the uplink port (if you have a single ten or gig port for all gig downside ports) . . ."

I would suggest, perhaps, or perhaps not. That would really depend on your client applications, i.e. how much traffic they will send/receive across the up-link path.

Do understand, some dual up-link solutions do not use both links actively. I.e. such are for redundancy, only.

Also understand, Etherchannel solutions allows joining of more than two links, although with a worst case hashing algorithm, only one link will be used.