Huawei Switch Stacking (iStack) and Cluster (CSS) Configuration Guide

Overview iStack (Intelligent Stack) is used on low‑end Huawei switches (S2700, S3700, S5700, S6700) to logically merge up to nine devices, while CSS (Cluster Switch System) provides similar functionality for high‑end switches (S7700, S9300, S9700) but supports only two devices. Both technologies virtualize multiple physical switches into a single logical unit.

iStack Roles 1. Master switch – the sole manager of the stack. 2. Standby switch – takes over if the master fails. 3. Slave switches – all other members, including the standby.

Stack ID and Priority Each member has a unique Stack ID (default 0) that influences port numbering (e.g., G0/0/1 becomes G2/0/1 when Stack ID is 2). Priority determines master/standby election; higher priority wins, with MAC address as a tiebreaker.

Physical and Logical Stack Ports Physical ports (model‑specific) carry stack protocol frames. Logical stack ports are bound to physical ports and are named Stack-port<ID>/1 and Stack-port<ID>/2 .

Connection Methods Stacks can be linked via dedicated stacking cards or factory‑defined 10 GbE ports, using SPF/SFP+ cables. Connections must be cross‑wired (e.g., port 1 on one switch to port 2 on the other).

iStack Configuration Example (S5700LI series)

Step 1 – Enable stack ports and bind physical interfaces:

[Huawei]stack port interface g0/0/28 enable

[Huawei]stack port interface g0/0/27 enable

[Huawei]interface stack-port0/1

[Huawei-stack-port0/1]port member-group interface g0/0/28

[Huawei-stack-port0/1]quit

[Huawei]interface stack-port0/2

[Huawei-stack-port0/2]port member-group interface g0/0/27

[Huawei-stack-port0/2]quit

Step 2 – Set stack IDs and priorities (SWA as master):

[SWA]stack slot 0 priority 200

[SWB]stack slot 0 priority 100

[SWC]stack slot 0 priority 100

[SWD]stack slot 0 priority 100

[SWA]stack slot 0 renumber 0

[SWB]stack slot 0 renumber 1

[SWC]stack slot 0 renumber 2

[SWD]stack slot 0 renumber 3

Step 3 – Save configuration and reboot each member:

[SWA]save

[SWA]reboot

Step 4 – Verify stack status:

[SWA]display stack

Direct‑Link Detection (DAD) Enable DAD on the two physical stack interfaces to detect split‑brain scenarios:

[HuaweiA-GigabitEthernet0/0/28]mad detect mode direct

[HuaweiB-GigabitEthernet0/0/27]mad detect mode direct

[Huawei]display mad verbose

CSS (Cluster Switch System) CSS shares the same concepts as iStack but supports only two devices and does not require cross‑wired logical ports. Roles, IDs, priorities, and MAC‑based election are identical.

CSS logical ports are named CSS-port<ID>/1 and CSS-port<ID>/2 . Configuration can be done via dedicated cluster cards or by repurposing regular business ports.

Example CSS enable and priority configuration:

[SWA]css enable

[SWA]set css priority 200

[SWA]set css id 1

[SWB]css enable

[SWB]set css priority 100

[SWB]set css id 2

Save and reboot, then verify with:

[SWA]display css status all

CSS also supports DAD detection on the physical cluster interfaces using the same mad detect mode direct command.