Hmm... 373035-B21 is a serial connection adapter for HP RJ-45 KVMs. I would not expect it to work with a KVM of another brand, as to the best of my knowledge, the KVM protocols over RJ-45 cables are not standardized between manufacturers at all.
That said, all the models you mentioned (rp7400, rp4400 and rp3440) have a built-in management processor which offers full console functionality over the network, independent of the OS.
The management processor will always be running as long as the server receives power. You can use it to remotely power down the server, and later power it back up again the same way.
The management processor has its own network interface, which is not visible to the server OS at all. To set up its IP address and other network parameters, you use the local serial console (press Ctrl-B on the console to access the management processor command prompt).
In rp7400 it might still be called "GSP": the older management processor type, with telnet and web access with low-grade encryption.
The rp3440 and rp4400 both have MP/iLO, the modernized version of the management processor. It offers SSL-secured web GUI and command line access with both telnet and SSH protocols (a license may be required to enable the SSH option).
The thing is, in all these models, the serial console is also routed through the management processor. If the MP fails for some reason, the serial console is likely to be non-functional too. So adding the serial console access over the KVM does not really give you much extra reliability over using the MP's built-in LAN console connection.
The MPs are usually pretty robust, assuming that you have kept the MP firmware reasonably up to date. Some early firmware versions had some problems, but they were usually curable by rebooting the MP, which can be done independent of the server OS.
If you can login to the server over the regular network interfaces and get root access, you can command the OS to signal the MP to reboot itself. Failing that, there is usually a physical reset button for the MP only. (It may be located next to the TOC button that is used to crash&reboot the server - don't press the wrong one!)
If I recall correctly, accessing the MP reset button in a rp4400 may require poking through an air exhaust hole in a specific location. The MP reset button location is detailed in the hardware manuals for your server: read them.
MK
MK
