To stack or not to stack?

[Rob_D]

Hi,

 

Most of our switches aren't stacked (and none of the newer ones have been), but we have a couple of cabs where there are some legacy switch stacks.

Now we're looking at replacing a lot of our older switches including the ones that are stacked.

Reading around, I can't find much benefit to stacking aside from management, and the stacks have uplinks from each switch in the stack back to the core.

 

So what are the benefits of keeping them as stacks when we replace them? We're looking at replacing 3Com SuperStack 5500 series with Aruba 6100 series - yes, I know the Aruba 6100s don't stack so we'd have to get another model if we wanted to keep the stacks.

[Steve21]

I guess it depends on the type of stack (management vs backbone etc) and things like uplinks.

 

For example, if you have 3 switches stacked together, with 1 uplink each, and the transceiver/port on one stack breaks it'll still work through the other switches. Additionally, you "could" have things double uplinked into stack if you have things like AX wifi etc that requires more than 1Gb which would then give it extra redundancy etc

 

Personally I'm not a fan of stacks "just" for management purposes, as generally find it's more likely to cause problems if something breaks than the odd time a firmware update etc needs doing across a stack, but for redundancy etc it's always a good option if you can

 

Steve

[Davit2005]

Hi,

 

Most of our switches aren't stacked (and none of the newer ones have been), but we have a couple of cabs where there are some legacy switch stacks.

Now we're looking at replacing a lot of our older switches including the ones that are stacked.

Reading around, I can't find much benefit to stacking aside from management, and the stacks have uplinks from each switch in the stack back to the core.

 

So what are the benefits of keeping them as stacks when we replace them? We're looking at replacing 3Com SuperStack 5500 series with Aruba 6100 series - yes, I know the Aruba 6100s don't stack so we'd have to get another model if we wanted to keep the stacks.

 

It is not just management that can be a benefit of stacking, true there are switches that only stack for management. Some benefits of true stacking i.e. one logical switch below.

 

Ability to configure LAG across different switches (normally spanning tree would block a link to avoid loops)

Layer3 routing redundancy (no need to rely on VRRP for Layer 3 routing redundancy)

Lack for need of complicated spanning tree setups to split load (i.e. mulpiple spanning tree instances)

Traffic on LAGs split between different Switches

Management

 

Bear in mind that firmware updates depending on model of switch can be different experiences.

Edited June 25, 2021 by Davit2005

[sonofsanta]

Cuts down massively on the expensive 10GbE ports needed at your core if three stacked switches can all communicate via one piece of fibre!

[Davit2005]

Cuts down massively on the expensive 10GbE ports needed at your core if three stacked switches can all communicate via one piece of fibre!

 

It can do the issue is that you lose some redundancy i.e. if top and bottom switches are uplinked to something else and the middle member fails you then lose middle only. Ideal configuration for more than 2 switches is a ring then uplinks top and bottom to stop a member being isolated.

Edited June 25, 2021 by Davit2005

[sonofsanta]

It can do the issue is that you lose some redundancy i.e. if top and bottom switches are uplinked to something else and the middle member fails you then lose middle only. Ideal configuration for more than 2 switches is a ring then uplinks top and bottom to stop a member being isolated.

 

 

Any stack would always be configured in a loop i.e. 1-2, 2-3, 3-1, and if you have the capacity for redundant links you can use them--we used to have 6 x 1Gbps connections from a stack going back to the core in a team. We could lose both uplinks on, say, switch 2, and the devices connected there would be fine to get their traffic via the other uplinks.

[ITGURU]

Only stacking I use is for the core switches for full redundancy.

[Rob_D]

It can do the issue is that you lose some redundancy i.e. if top and bottom switches are uplinked to something else and the middle member fails you then lose middle only. Ideal configuration for more than 2 switches is a ring then uplinks top and bottom to stop a member being isolated.

As I said originally, the stacks have uplinks form each switch in the stack anyway.

[Davit2005]

As I said originally, the stacks have uplinks form each switch in the stack anyway.

 

I was merely pointing out for clarity jus in case anyone were to see this thread later on

 

May of mis-interpreted an earlier post apologies for that.

 

We have deployed lots of VSF stacks now.

 

From using 2 switches in a VSF stack as a top of rack design with the edge switches (non-stackable) split between both i.e. LAG from each edge switch using the 1Gb uplink split between each member switch in the ToR stacked switches or having multiple stacks of 8 switches connected to a 5406 and split top and bottom of each stack between different SFP+ modules using DAC cables.

 

Going forward it will prob be our core design with a stacked core with layer 3 from closer to edge then do away with all our in depth Spanning tree setup, lol.

Edited June 25, 2021 by Davit2005

[Chris_Cook]

I certainly wouldn't say its a bad thing or that it doesn't have its place, but I'm not sure its really necessary for a school.

 

It does depend on how you weigh up cost and complexity vs reliability and performance.

 

Personally, I'd rather keep things simple and have centralised management like Unifi.

 

A non-stacked setup can still be extremely reliable provided its installed and cabled properly, and using quality equipment and cables.

 

Maybe in a newer building with larger, more centralised racks it would be different.

 

At the risk of causing another argument, I'd also look at how many unused ports you have patched in, and whether you need that many live switch ports to support your devices.

[QW3RTY]

At my place, we're quite stack crazy. Across 6 floors, we have a stack for each floor. It's not essential but we felt it was worth the extra cash buying the stacking cables (The switches we have, HPE 5130s, support stacking natively so they only additional cost is the stacking cables

 

It simplifies accessing them and memorising IP addresses, previously were I worked a comms room would have 8 or so different IP addresses to SSH into each switch whereas with a stack it allows all switches on that floor to be managed through a single IP address. The uplinks are part of a link aggregation group and spread across the switches to make sure traffic can still flow even if a switch dies.