H3C S5120-EI Series Operation Manual page 1142

Ring connection: Given a device, its logical stack port 1 is connected to logical stack port 2 of
another device, and its logical stack port 2 is connected to logical stack port 1 of a third one, as
shown in Figure 1-2.
Figure 1-2 Physical connections of IRF stack
Master
Slave
IRF
Slave
Slave
Bus connection
A ring connection is more reliable than a bus connection. The failure of one link in a ring connection
does not affect the function and performance of the stack, whereas the failure of one link in a bus
connection causes the split of the stack.
You can connect at most four S5120-EI series Ethernet switches to form a stack.
Correspondence between a logical stack port and a physical stack port
The connection of logical stack ports is based on that of physical stack ports; therefore, you need to
bind a logical stack port with physical stack port(s). A logical stack port can be bound to one physical
stack port or, to realize link backup and bandwidth expansion, bound to two physical stack ports
(aggregated as an aggregate stack port).
You need to specify the correspondence between a logical stack port and physical stack port(s) through
command line. When you specify that a logical stack port is bound to one physical stack port, the serial
number of the physical stack port bound to logical stack port 1 must be smaller than that of the physical
stack port bound to logical stack port 2; when you specify that a logical stack port is bound to two
physical stack ports (aggregate stack port), these two physical stack ports must be on the same
module.
As shown in Figure 1-3. Switch A connects to Switch B and Switch C through logical stack ports
IRF-port 1 and IRF-port 2 respectively.
Master
IRF
Slave
Ring connection
The orange lines in the figure represent stack
cables, which are different from common Ethernet
network cables. The stack cable can be composed
of either one physical cable or multiple physical
cables.
1-3
Slave
Slave