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I am planning the network for our new offices this time utilising Cisco 3750X's (WS-C3750X-48P-S). The required port count has gone up and up so have had to procure some extra switches to bring the count to 8.

Now this is NOT a traffic heavy network, but rather just one with lots of patch ports everywhere due to being a flexible/multi use environment where we allow for different desk/layout conigurations. So we put ports everywhere.

I am planning to stack all 8 using Stackwise Plus which provides 64Gbit/s of ring bandwidth plus local switching. I have previously been aware of potential performance issues when running large stacks, but this may have been with the original stackwise or when people were running open loops.

Is there any key factor here that would make me want to break this 8 stack into a 2 x 4 config instead?

Thanks

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  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Dec 15, 2019 at 5:57

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First, be sure to understand that the End of Software Maintenance Releases Date for that device was October 30, 2017, so you will get no more software releases, except for Vulnerability/Security Support, and the End of Vulnerability/Security Support is October 30, 2019, effectively ending all software support for that device model. The Hardware Last Date of Support is October 31, 2021. You should be planning to move to a later switch model (the new 9K switches have a guaranteed 10-year lifespan).

The 3750X can stack up to nine switches in a stack, and it should work just fine with eight switches as you have described.

The one thing to consider when stacking more than five switches is the size of the network address range When you have five 48-port switches, that is 240 ports in a stack, and that fits well for a /24 network that many people use. If you have more switch ports than that in a stack using a /24 network, you could exhaust the network addressing if you connect more hosts to the switch stack. If you will have more connection than Your network addressing can handle, you may get a nasty surprise. I have seen this problem firsthand when people stack six switches, then add too many devices, and not all the devices can get addressing. You may need to consider using a /23 network for such a large stack.

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  • Thanks, and yes I am aware the switches have gone EOL, not an issue here. This stack will be a L3 deployment routing about 7 VLAN's + an uplink to a firewall as its default route so the advice RE a single /24 is not applicable (and also networking basics 101 hehe).
    – tomstephens89
    Jul 29, 2019 at 13:00
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    Right. I have just seen too many people get surprised when their large switch stack doesn't work because the number of ports exceeds the network size. Those are usually very experienced network engineers who simply forget to check that when building the network. Other than that, there should be no problem with a stack of eight 3750X switches.
    – Ron Maupin ♦
    Jul 29, 2019 at 13:03

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