Technology Services Networking owns and maintains the network switches that connect buildings to the Urbana campus network. Beginning in 2024, Networking is changing the standard type of switch deployed from a modular chassis-based form factor to fixed form factor switches in a "stack" configuration. This article is intended to assist IT Pros in understanding the changes. 

Why is the type of switch changing?

In 2023, Technology Services Networking completed a comprehensive evaluation to select the next generation of campus switches. Some of the requirements that were considered include faster connection speeds to client devices, greater Power over Ethernet capacity, and increased switch uplink capacity and redundancy. Several chassis-based form factor switches were considered, but our evaluation concluded that a fixed form factor arrangement would better meet the needs of the campus network for the foreseeable future.

What is a switch "stack?"

A switch "stack" is a series of fixed form factor (1RU) switches that are interconnected with each other and configured to logically behave as a single switch. A switch stack is comprised of 1 to 10 physical switches that are referred to as stack "members." When a CER is upgraded to stacking switches, one stack will be created for each rack within the CER. This means that if a CER contains four racks of patch panels, one stack will be installed in each rack for a total of four stacks. Each stack has dual (redundant) 50Gbps interconnects to other stack members and 25Gbps uplinks back to the building distribution device.

How are switch stacks and ports identified in Iris?

Switch stacks can be viewed from the Iris switch management tool like any other switch. When you view a switch from the "devices" page of Iris, every port that is available to you from every member of the stack will be displayed. 

Ports on stacking switches follow the numbering convention X/1/Z.

The first number (X) identifies the stack member, or the physical 1RU switch.

The second number identifies the module within the stack member. Since we deploy fixed form factor switches that do not have modules, this number will always be 1. 

The third number (Z) identifies the specific interface (or port) within the stack member.

For example, the interface listed in Iris as 3/1/17 can be found on switch stack member 3, port number 17. 

How are switch stacks physically labeled in a CER?

Every member switch of every stack will be labeled with the stack name and the interfaces/ports that are contained within that stack member. For example, a switch stack member in DCL may be labeled "sw-dcl5, ports 3/1/1 - 3/1/48". 

Switches are physically arranged in reverse order and increment upward; that is, stack member 1 is the bottom-most switch, and the highest member number will typically be the top-most switch. Although this may seem counter-intuitive at first, Technology Services made the decision to arrange the switches this way after consultation with campus IT Pros because it greatly simplifies the process of adding additional switch members in the future when more ports are needed.

The below diagram shows an example CER that has two racks, each with a switch stack. The text above each switch is identical to the physical label that would be attached to each switch stack member. The bottom stack member (member 1) of each stack also features port speeds greater than 1Gbps, which can be distinguished by the white border surrounding the ports.

What are the different types of ports available on stacked switches? 

Most switch stack members will contain 48 ports that support 1Gbps connections and class 4 Power over Ethernet (PoE ). The vast majority of jacks and devices will be patched to these switches, but additional switch member types are available to meet specific needs.

Stack members are also available that support greater speeds (for example, multi-rate 1/2.5/5Gbps and in some cases 10Gbps) and greater Power over Ethernet capacity (up to class 8). Because the cost per-port of these switches is greater, we ask that you only use these ports for the devices that require the enhanced features over the standard 1Gbps/CL4 ports). These enhanced ports can be identified by a white border surrounding the ports.

What if I have used all of the ports on a switch stack and need more ports?

One of the benefits of using switch stacks is that we are able to add additional members very easily. If you find that you do not have enough available ports to patch a jack, IT Pros can identify underutilized ports that can be re-used via Iris (Networking, Iris Scenarios: Running a Port Utilization report). If there are not enough ports available after re-using all available underutilized ports, please contact Technology Services Networking who will install additional stack members as needed.

Networking requests that jacks be patched to switches in the same rack as the patch panel as cross-patching jacks to a different rack can make maintenance more difficult, especially during an outage. If you find that there are no available ports in the same rack as the patch panel you need to patch, please contact us first before cross-patching to a different rack. In most cases, we will provide a list of unused ports or add additional switch stack members to eliminate cross patching.

I have additional questions

If you have any questions about switch stacks or the campus network in general, Technology Services Networking is happy to help. Please contact us through the UIUC Help Center or by e-mail at consult@illinois.edu.