3Com 4210G Series Configuration Manual page 1099

An IRF typically has a bus connection or a ring connection:
Bus connection: Given a device, its IRF port 1 is connected to IRF port 2 of another device, and its
IRF port 2 is connected to IRF port 1 of a third one; devices are connected to form a single straight
connection, as shown in
Ring connection: Given a device, its IRF port 1 is connected to IRF port 2 of another device, and
its IRF port 2 is connected to IRF port 1 of a third one, as shown in
Figure 27-3 Physical connections of IRF
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 IRF, whereas the failure of one link in a bus
connection causes the split of the IRF.
You can connect at most four Switch 4210G series switches to form an IRF.
Correspondence between an IRF port and a physical IRF port
The connection of IRF ports is based on that of physical IRF ports; therefore, you need to bind an IRF
port with physical IRF port(s). AN IRF port can be bound to one physical IRF port or, to realize link
backup and bandwidth expansion, bound to two physical IRF ports (aggregated as an aggregate IRF
port).
You need to specify the correspondence between an IRF port and physical IRF port(s) through
command line. When you specify that an IRF port is bound to one physical IRF port, the serial number
of the physical IRF port bound to IRF port 1 must be smaller than that of the physical IRF port bound to
IRF port 2; when you specify that an IRF port is bound to two physical IRF ports (aggregate IRF port),
these two physical IRF ports must be on the same module.
As shown in Figure 27-4. Switch A connects to Switch B and Switch C through IRF ports IRF-port 1
and IRF-port 2 respectively.
Figure 27-3.
26-4
Figure 27-3.