HP 4800G Series Configuration Manual page 1943

If only one single-port interface module is installed, the device can be used only as Switch B or
Switch C in Figure
In this situation, because only one IRF port is needed on Switch B or Switch C, IRF-port 2 or
IRF-port 1 can be bound to any physical port on the device.
2) IRF port correspondence for two interface modules
Correspondence in non-aggregate mode
Figure 1-6 Correspondence in non-aggregate mode for two interface modules
When two dual-port interface modules are installed, if the correspondence is not in the aggregate mode,
you can bind an IRF port to any physical IRF port
must ensure that the serial number of the physical IRF port bound to IRF-port 1 is smaller than that of
the physical IRF port bound to IRF-port 2, namely, the physical IRF port bound to IRF-port 2 should be
located on the right side of the physical IRF port bound to IRF-port 1. The two physical IRF ports bound
to the IRF ports can be located either on one interface module or on different interface modules.
If two single-port interface modules are installed, you need to bind IRF-port 1 to physical IRF port 1,
and IRF-port 2 to physical IRF port 3.
If one dual-port interface module and one single-port interface module are installed, the
correspondence is the same with that when you install two dual-port interface modules. In this
situation, IRF-port 2 or IRF-port 1 can be bound to any physical port on the device, because only
one IRF port is needed on Switch B or Switch C.
Correspondence in aggregate mode
1-4, that is, the device should be at either end of a bus connection.
1-6
(Figure 1-6 only shows one possibility). However, you