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New Member

RJ-45-to-DB-25 Adapter

As cisco says that: "RJ-45-to-DB-25 Adapter connects a router to PC through a serial port".

If I want to use this cable, what com number should I use for the female 25 pins port on PC ? Because i tried com2 and com3 it did not work.


Re: RJ-45-to-DB-25 Adapter

The 25 pin port on most PCs is a Parallel port to connect a printer.

You cannot use the 25pin port on a PC to communicate serially to any device.

The 25pin adapter is usually to connect to some older Cisco Supervisor cards (Cat5K/5500, 6500 ...).

Usually you'd connect to the PC with a 9pin adapter, through the blue or black rolled cable into the Cisco device.

Over the years, Cisco has used a number of interfaces, some of which were 25 pin, most were RJ45, maybe even a few 9 pin connectors.

Good Luck


New Member

Re: RJ-45-to-DB-25 Adapter

Thanks Scott

I have just realized, that I should not have submitted this thread, because as you said that the port with 25 pins in our today PCs are parallel port not serial (Here I have confused).

But one more thing, the serial ports for an old PCs (as far as I remember) were 25 pins male (not femal),,,,Am I right ? If so why then has the cisco cable (equiped with router) got 25 pins male !!!!

Note: See the figure in the link above, it shows us 25 pins femal (it should be) not male (it should not be).