Catalyst 9300: StackWise-480 vs StackWise Virtual

Catalyst 9300 gives you two ways to make more than one switch behave as one, and the names invite confusion because one is a stacking cable and the other is a virtualisation feature built on fibre links. Choosing wrongly shows up later as a cable-length limit nobody planned for, or an upgrade process that needs a full stack reload. This article compares StackWise-480, StackWise-1T, StackWise Virtual and the older VSS, with the platform facts that drive the choice.

The Options

The 9300 is a fixed access switch and does not support VSS; StackWise Virtual on the 9300/X family is the modern equivalent, and it combines two switches over standard fibre with a dedicated virtual link. The default back stack interfaces run at 480 Gbps on Catalyst 9300 and 9300X, while homogeneous 9300X stacks can reach higher aggregate bandwidth.

StackWise-480 / 1T in Practice

• Members are limited by the stacking cable lengths available, which is the practical reason a stack cannot span buildings.
• Power and data share a single management plane: one console, one IP, one running configuration for the whole stack.
• Adding or replacing a member triggers a stack-wide reload in many topologies, so plan maintenance windows accordingly.
• Verify before deploying: show switch, show switch stack-ports, show switch stack-ring activity-detail.

StackWise Virtual in Practice

! core switch preconfiguration (SVL) - both members
switch 1 priority 1
stackwise-virtual domain 1

interface range FortyGigabitEthernet1/0/1-2
 stackwise-virtual link 1

interface TenGigabitEthernet1/0/1
 stackwise-virtual dual-active-detection

show stackwise-virtual
show stackwise-virtual link
show stackwise-virtual dual-active-detection

Two details decide whether a split brain causes an outage: the dual-active detection links must run through a path that does not share fate with the SVL, and the priority must be set so a predictable member wins. Without dual-active detection, a failed SVL leaves both switches active - which for a first-hop gateway means duplicate IP addresses on the wire.

Which to Choose

1. Single rack or adjacent racks, simple build: StackWise-480 with stacking kits. Lowest complexity, highest port density per management IP.
2. Switches in different racks or closets, existing fibre: StackWise Virtual. No special cables, longer reach, and per-member independent forwarding.
3. Legacy distribution or core with 6500/4500 heritage: VSS, if you already run it - but new deployments belong on SVL.
4. Anything requiring more than two switches in one logical unit: StackWise. SVL is strictly a pair.

Upgrades and Failure Tests

• Test a split-stack scenario in the lab: pull the stacking cable or SVL link and confirm the documented dual-active behaviour, not your assumption about it.
• For SVL, verify which image each member boots and that the second member can switch over cleanly during an upgrade.
• Check bandwidth headroom: show switch stack-ring activity-detail shows traffic per stack port - a saturating ring is a design problem, not a hardware fault.

Related reading: Catalyst 9300 StackWise vs StackWise Virtual, Catalyst 9300 split-stack troubleshooting and Catalyst 9300 stack bandwidth: 320, 480 and 1T.

原文链接：Cisco: Catalyst 9300 StackWise system architecture white paper