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[aprssig] RJ45/RS232 Again

Daron J. Wilson daron at wilson.org
Mon Mar 13 22:03:29 UTC 2006


>     I use Cisco rollover cables a lot because I teach computer networking.
> I want to make an adapter to adapt the leads in a Cisco rollover cable to
> the RS232 interface on a TNC-2.  Therefore, the same cable I use to
> interface to Cisco devices I will be able to use [with this adapter] to
> connect to the RS232 port on a TNC-2.
> 
>     A rollover cable is called just exactly what the pin out describes.
> It
> is as follows:
> 
>                      RJ45   to  RJ45
>                        1    to    8
>                        2    to    7
>                        3    to    6
>                        4    to    5
>                        5    to    4
>                        6    to    3
>                        7    to    2
>                        8    to    1
> 
>     Generally, you have a DB9 to RJ45 female adapter on your computer's
> serial port, a rollover cable, and then the other end of the rollover
> cable
> mates with the console (serial) port on a Cisco device.

OK, so I quickly grabbed my Cisco console cable and DB 9 adapter, took it
apart, and this is what I see:


Cisco DB9       Modular    Rollover        Modular          TNC DB25
to Modular      Plug       Modular cable   Plug             to Modular
Adapter                                                     Adapter


1 - NC
2 --------------- 6 ------------------------ 3 --------------- 2 - TD
3 --------------- 3 ------------------------ 6 --------------- 3 - RD 
4 --------------- 2 ------------------------ 7 --------------- 6 - DSR
5 --------------- 4,5 ----------------------5,4 -------------- 7 - SG
6 --------------- 7 ------------------------ 2 --------------- 20 - DTR
7 --------------- 1 ------------------------ 8 --------------- 5 - CTS
8 --------------- 8 ------------------------ 1 --------------- 4 - RTS
9 - NC

I didn't take the time to build one up, but that is what looks logical to me
at first glance.

Hopefully that is right, let us know one way or the other.

Good luck!

N7HQR





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