S6720-LI and S6720S-LI Service Port Stacking Support

For the cables that can be used as stack cables, see "Cables" in the Hardware Description. Using other cables may cause exceptions in the stack system, for example, frequent error-down events on stack ports.
Combo ports cannot function as stack member ports.
For stacking-supported service ports, some of them can be used as stack ports, whereas some can be used as ordinary service ports.
Since V200R011C10, S6720-LI and S6720S-LI series switches can set up stacks in service port stacking mode using dedicated stack cables.
The number of stacked switches is recommended to be 2 to 9.

**Table 1** Service port stacking support
Device Series	Port Supporting Stacking	Stack Cable	Rate of a Single Port	Remarks
S6720-LI and S6720S-LI	40GE ports on the front panel	1 m, 3 m, and 5 m QSFP+ passive high-speed copper cables QSFP+ optical module (QSFP-40G-SR-BD not supported) and optical fiber 10 m QSFP+ AOC cable	40 Gbit/s	A stack can be set up between S6720-LI models and between S6720S-LI models, but a stack cannot be set up between S6720-LI and S6720S-LI. When 40GE ports on the front panel are used as stack ports, a switch supports a maximum of two logical stack ports, and each logical stack port supports a maximum of two stack member ports. Each switch can use a maximum of two service ports as stack member ports. When 10GE optical ports on the front panel are used as stack ports, a switch supports a maximum of two logical stack ports, and each logical stack port supports at least one stack member port and at most eight stack member ports. A switch supports a maximum of 16 stack member ports. Two rate of ports on an S6720-LI or S6720S-LI can both be configured as stack member ports, but each logical stack port contains only the same rate of stack member ports. 40GE ports do not support the stacking function after they are split into 10GE ports. If stack member ports on the front panel are connected using 1 m, 3 m, or 5 m QSFP+ passive high-speed copper cables, their working speed can be increased to 48 Gbit/s using the stack port speed command. After their working speed is increased to 48 Gbit/s, switches using these ports cannot set up a stack with switches using ports with the working speed 40 Gbit/s. Only the last 16 10GE ports on the front panel can be used to set up a stack using dedicated stack cables.
S6720-LI and S6720S-LI	10GE optical ports on the front panel	1 m, 3 m, and 5 m SFP+ passive high-speed copper cables 10 m SFP+ active high-speed copper cables 3 m and 10 m AOC cables 10GE SFP+ optical module and optical fiber 0.5 m and 1.5 m SFP+ dedicated stack cables (supported in V200R011C10 and later versions)	10 Gbit/s