Determining the Stack Topology

Networking for a Stack of More Than Two Member Devices

A stack can be connected in a chain or ring topology depending on the stack connection mode, as shown in Figure 1. Table 1 compares the two stack topologies in terms of reliability, link bandwidth utilization, and convenience of cable connections.

Figure 1 Stack topologies

**Table 1** Comparison between stack topologies
Stack Topology	Advantages	Disadvantages	Applicable Scenario
Chain topology	Applicable to long-distance stacking because the first and last member switches do not need to be connected by a physical link.	Low reliability: If any stack link fails, the stack splits. Low stack link utilization: The entire stack relies on a single path.	Member devices are far from one another and a ring topology is difficult to deploy.
Ring topology	High reliability: If a stack link fails, the topology changes from ring to chain, and the stack can still function normally. High link bandwidth efficiency: Data can be forwarded along the shortest path.	The first and last member switches need to be connected by a physical link, so this topology is not applicable to long-distance stacking.	Member switches are located near one another.

Networking for a Stack of Two Member Devices

Two devices can set up a stack in a chain topology, as shown in Figure 2. In this topology, only one logical stack port exists between the two devices and no loop exists in the stack.
Figure 2 Only one logical stack port between two member devices
Two devices can set up a stack with back-to-back networking, as shown in Figure 3. In this networking, two logical stack ports exist between the two devices, and one loop exists in the stack, which will be automatically eliminated by the system.
Figure 3 Two logical stack ports between two member devices

When using two devices to set up a stack, you are advised to do as follows:

If the devices provide no more than 28 ports, use the networking with only one logical stack port. Otherwise, use the back-to-back networking.
If more member devices need to be added to the stack in the future, use the back-to-back networking, which will require minimum modification to the existing system.
Connect at least two stack cables between the two devices to ensure reliability.