Catalyst 9300 Stackwise stack ports connection

[Engineer-US]

Hi,
I have a quick question regarding the Stackwise configuration for 4 Catalyst 9300 switches. In terms of connecting them, which scenario would be correct:
Connect switch 1 stack port 2 to switch 4 stack port 1

OR
Connect switch 1 stack port 1 to switch 4 stack port 2
Could you please clarify which connection method is preferred and the reasons behind it?
Thank you

[Leo Laohoo]

Go HERE.

[DanielP211]

Hello,

Always imagine connecting everything in an X shape. So stack switch 1 port 2 goes to stack switch 4 port 1.

BR

[Engineer-US]

Thank you DanielP211 and Leo Laohoo for the reply.
I have a question about the implications of connecting Switch 1 stack port 1 to Switch 4 stack port 2.
I’ve noticed that some of our stacks are configured in this manner, and I would like to understand the potential impact or any issues that might arise from this setup.

[Reza Sharifi]

Hi,

I would like to understand the potential impact or any issues that might arise from this setup.

The will be no operation issues. Cross connecting is the recommend and cleaner solution.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/hardware/install/b_c9300_hig/Installing-a-switch.html

HTH

[Joseph W. Doherty]

BTW, if you don't want to purchase the optional longer cable for the Stackwise the connection between top and bottom switches (1 and 4?), you can connect connect switch 1 to switches 2 and 3 and switch 4 to switches 2 and 3.

[Engineer-US]

Interesting.

[vishalbhandari]

In a Stackwise configuration for 4 Catalyst 9300 switches, the preferred connection scenario is:

Connect switch 1 stack port 1 to switch 4 stack port 2.

Reasoning:

1. Closed Loop/Full Ring Topology:

   • Stackwise operates in a full-duplex ring topology, where all switches are connected in a ring. Each switch should have two connections: one to the switch "above" and one to the switch "below." This ensures redundancy and resilience in case one of the connections fails.
   • Connecting switch 1's stack port 1 to switch 4's stack port 2 ensures that the ring is closed, providing fault tolerance.

2. Bandwidth and Redundancy:

   • The full ring setup maximizes bandwidth by allowing traffic to flow in both directions. If a link or switch fails, the stack can still communicate using the other path.

3. Improved Performance and Reliability:

   • By connecting switches in a consistent manner (e.g., port 1 to port 2 in a loop), the Stackwise architecture can better manage traffic and distribute bandwidth evenly.

Thus, connecting switch 1 stack port 1 to switch 4 stack port 2 is part of the full-ring best practice for a resilient stack configuration.

[Joseph W. Doherty]

Could you expand upon your point #3, because as far as I know Stackwise architecture only benefits from a ring, i.e. it matters not how switches are interconnected for performance or reliability providing the ring.

Of course, a clean and standard way of connecting Stackwise can improve manual/human performance and reliability.  (Much as structured cabling does too.)

[Joseph W. Doherty]

Oh, since OP specifically mentioned the 9300, as did @vishalbhandari, adding its architecture, a Cisco White Paper about 9300 series Stackwise architecture is: https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9300-series-switches/white-paper-c11-741468.html.  I don't believe that paper touches upon how stack member switches are actually interconnected but assumes they are (somehow) connected to form a ring.

BTW, if a Stackwise performance is a consideration, you really need to understand it, and depending on your performance needs may find you need another switch architecture.  In general, Stackwise isn't an ideal architecture for a (many) multi member stack with lots of stack traffic especially if multicast/broadcast.  Stackable switches often lack other hardware resources and/or capabilities often found in chassis switches.

[vishalbhandari]

By connecting switches in a consistent manner, such as linking port 1 to port 2 in a loop, the Stackwise architecture ensures optimal traffic management across the entire stack. This configuration creates a resilient, high-speed ring topology where data can travel in both directions, allowing for dynamic load balancing. In the event of a link failure or switch malfunction, the Stackwise system reroutes traffic seamlessly, preventing downtime and ensuring continued connectivity. Additionally, it enhances bandwidth distribution, as the interconnected switches can effectively aggregate and balance the load, maximizing the overall throughput and providing a more reliable, scalable network infrastructure.

[Joseph W. Doherty]

@vishalbhandari thank you for your follow up reply but I suspect you misunderstood what expansion of information I sought.

I'm not questioning the benefits of a Stackwise ring I'm questioning the relevance of ". . . connecting switches in a consistent manner. . .".

Again, how does selecting the Stackwise port interconnections, in any manner, forming the ring, impact the functioning of the ring?

I'm saying it doesn't.

Also, again, there is benefits to how Stackwise are interconnected but they are on the same level as using different color Ethernet copper cables.  Or another example of a similar policy which makes no difference to actual stack operation, stack members are numbered sequentially, by increments of 1, starting with 1, top to bottom then left to right.  Each member is also externally labeled with its name and member number.

If you do have such information, please provide it.

[Engineer-US]

I've been reviewing the Cisco documents regarding stacking data cable connections, and I noticed that they outline three different ways to connect these cables. The only distinction they've provided between these methods pertains to the Upgrade Process Sequence.
Does anyone have experience with these methods and which one is considered best practice and why?

Introduction to StackWise
Figure 1 shows the StackWise-1T/480/320 technology when four switches are part of the stack.
https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9300-series-switches/white-paper-c11-741468.html#IntroductiontoStackWise

Data Stack Cabling Configurations
Figure 2. Data Stacking the Switches in a Rack or on a Table Using the 0.5-meter StackWise Cables
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/hardware/install/b_c9300_hig/Installing-a-switch.html#concept_971E5E644A094ABEB52C4911E6BA154B

Data Stack Cabling Configurations
Figure 2-1 Data Stacking the Switches in a Rack or on a Table Using the 0.5-meter StackWise Cable
Figure 2-2 Data Stacking the Catalyst 3750-X Switches in a Rack or on a Table Using 0.5-meter and 3-meter StackWise Cables
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/hardware/installation/guide/3750x_3560x_HIG/HIGINSTL.html#wp1348052

Rolling Stack Upgrade
Upgrade Sequence Examples
Figure 1-4 Stack Port 1 on Member 1 is Connected to Member 9
Figure 1-5 Stack Port 1 on Member 1 is Connected to Member 2
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-0_2_se/configuration/guide/3750x_cg/swstack.html#59795