Anyone that's ever had the joy of trying to console into an APC SmartUPS probably realized they do things a little odd. Baud rate of 2400 and a special cable that doesn't work with anything else. I needed a standard rollover cable to DB9 pinout so I could make some adapters.
The top table here shows the pinout for DB9 to DB9, which I then used to make my adapter.
Cisco has a nice page here that shows what each pin does on a rollover cable, look for the table called "RJ-45 Port Pin-outs."
The adapter I used was part AD-9MT8-G1.
Here's a table that shows the pinout for the adapter:
Connect the pins as shown in the table then cut off the rest of the pins, don't connect them.
What the final adapter looks like before putting it together:
Note: This was my first test adapter, you should only have pins 1,2 and 9 connected.