S5720-SI, S5720S-SI, and S5720I-SI 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.
After a UCL group is created using the ucl-group command on S5720-SI&S5720S-SI&S5720I-SI switches, a stack cannot be set up.
S5720-SI series switches are classified into S5720-P-SI and S5720-X-SI based on their uplink interface types.
S5720S-SI series switches are classified into S5720S-P-SI and S5720S-X-SI based on their uplink interface types.
MultiGE ports of an S5720-14X-PWH-SI-AC cannot be used as stack member ports.
In V200R010 and later versions, any models of S5720I-SI, S5720-SI and S5720S-SI can set up a stack. When different models need to set up a stack, they must use stack ports of the same type. That is, they either all use electrical ports on front panels or all use SFP+ or SFP optical ports. In V200R009 and earlier versions, S5720-14X-PWH-SI-AC cannot set up a stack with S5720S-SI or other S5720-SI models. The S5720S-SI can set up a stack with all S5720-SI models except S5720-14X-PWH-SI-AC.
Since V200R010, two SFP+ optical ports of an S5720-14X-PWH-SI-AC can be used as stack member ports. If SFP+ optical ports of an S5720-14X-PWH-SI-AC have been configured as stack member ports but the switch needs to be downgraded to V200R009 or an earlier version, delete the stack member port configuration of SFP+ optical ports before the downgrade. If this configuration is not deleted before the downgrade, a stack that cannot run normally will be set up after the downgrade. You need to disable the stacking function to delete the stack member port configuration of SFP+ optical ports.
Among S5720I-SI series switches, the S5720I-6X-PWH-SI-AC and S5720I-10X-PWH-SI-AC do not support the stacking function.
In a stack set up using electrical interfaces, when adding a new member switch or replacing a faulty member switch, to prevent a packet loop caused by a failure to add the new member in case of insufficient ACL resources, you are advised to configure the service ports used in both the new switch and the stack as stack ports before connecting the switch to the stack using cables.
Since V200R011C10, S5720-SI and S5720S-SI series switches can set up stacks in service port stacking mode using dedicated stack cables. S5720I-SI series switches of all versions 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
S5720-P-SI and S5720S-P-SI	Four SFP optical ports	1 m and 3 m SFP+ passive high-speed copper cables 5 m SFP+ passive high-speed copper cables (supported in V200R009 and later versions) 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	When SFP optical ports are used as stack ports, a switch supports a maximum of two logical stack ports, and each logical stack port contains one or two stack member ports. Each switch can use a maximum of four service ports as stack member ports. When a logical stack port contains two stack member ports, the logical stack port can contain only stack member ports 1 and 2 or stack member ports 3 and 4. When electrical 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.On a switch with 48 electrical ports, the first and last 24 ports must be added to two separate logical stack ports to ensure that a stack can be set up successfully. Since V200R010, if stack member ports are connected using 1 m or 3 m SFP+ passive high-speed copper cables, their working speed can be increased to 12 Gbit/s using the stack port speed command. After their working speed is increased to 12 Gbit/s, switches using these ports cannot set up a stack with switches using ports with the working speed 10 Gbit/s.
S5720-P-SI and S5720S-P-SI	Electrical ports on the front panel	Category 5 or higher network cable	1 Gbit/s
S5720-X-SI and S5720S-X-SI	Four SFP+ optical ports	1 m and 3 m SFP+ passive high-speed copper cables 5 m SFP+ passive high-speed copper cables (supported in V200R009 and later versions) 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	When SFP+ optical ports are used as stack ports, a switch supports a maximum of two logical stack ports, and each logical stack port contains one or two stack member ports. Each switch can use a maximum of four service ports as stack member ports. When a logical stack port contains two stack member ports, the logical stack port can contain only stack member ports 1 and 2 or stack member ports 3 and 4. When electrical ports or downlink SFP 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.On a switch with 48 electrical ports, the first and last 24 ports must be added to two separate logical stack ports to ensure that a stack can be set up successfully. Since V200R010, several new S5720-X-SI models (S5720-28X-SI-24S-AC, S5720-28X-SI-24S-DC, S5721-28X-SI-24S-AC, and S5720-52X-SI-48S) providing downlink SFP optical ports are available. These switches allow using downlink SFP optical ports on the front panel as stack member ports. If one member switch uses downlink SFP optical ports as stack member ports, all the other member switches must also use downlink SFP optical ports as stack member ports. Since V200R010, if stack member ports are connected using 1 m or 3 m SFP+ passive high-speed copper cables, their working speed can be increased to 12 Gbit/s using the stack port speed command. After their working speed is increased to 12 Gbit/s, switches using these ports cannot set up a stack with switches using ports with the working speed 10 Gbit/s.
	Electrical ports on the front panel	Category 5 or higher network cable	1 Gbit/s
	Downlink SFP optical ports on the front panel	GE SFP optical module and optical fiber	1 Gbit/s
S5720I-SI	Four SFP+ optical ports	3 m SFP+ passive high-speed copper cables 10GE SFP+ industrial optical module and optical fiber 0.5 m and 1.5 m SFP+ dedicated stack cable	10 Gbit/s	S5720I-SI series can set up stacks with any S5720-SI and S5720S-SI models. When different models need to set up a stack, these models must use stack ports of the same type. That is, they either all use electrical ports on front panels or all use SFP+ optical ports. When SFP+ optical ports are used as stack ports, A switch supports a maximum of two logical stack ports, and each logical stack port contains one or two stack member ports. Each switch can use a maximum of four service ports as stack member ports. When electrical 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. If stack member ports are connected using 3 m SFP+ passive high-speed copper cables, their working speed can be increased to 12 Gbit/s using the stack port speed command. After their working speed is increased to 12 Gbit/s, switches using these ports cannot set up a stack with switches using ports with the working speed 10 Gbit/s.
S5720I-SI	Electrical ports on the front panel	Category 5 or higher network cable	1 Gbit/s