DB9 modem to router cabling

Unanswered Question
Jun 12th, 2008


I am wondering exactly what cables/adapters work best to connect a DLINK DFM-560e modem (or any modem that has a DB9 adapter, NOT a DB25) to the RJ45 aux port of a 2800 series Cisco router for OOB access. Thanks.

I have this problem too.
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rtheobald Thu, 06/12/2008 - 12:50

FYI - I see various documentation on the cisco website describing cabling required for connecting modem with DB25. However, I can't find ANYTHING for connecting modem with DB9. Thanks again.

michael.leblanc Fri, 06/13/2008 - 09:57

Several years ago I made my own adapter to connect the aux port on a c1710 with a Global Village modem (used with my first Mac in 1994).

You can but an RJ45 to DB-9 adapter at a local electronic supply store and wire it to your needs.

The attached .pdf file show's the pin-outs I used.

Note that the table shows "both" RJ pins 4 and 5 tied to DB pin 5 (GND), this is NOT an error in the table.

Your aux port is probably the same as mine, but you might want to check the Cisco docs to be sure (i.e.: same signal on same pin).

Good luck.

hennigan Sun, 06/15/2008 - 00:37

I've always had to make them.

Option 1: You will need an old-school flat console rollover cable with RJ-45 on both ends and an adapter hood with male DB-9 to RJ45 pinned as follows:

Color RJ-45 DB-9 Function

Blue 1 8 CTS

Orange 2 6 DSR

Black 3 2 RD

Red 4 5 Ground

Green 5 5 (see note) Ground

Yellow 6 3 TD

Brown 7 4 DTR

White 8 7 RTS

Note: both of these connect to ground, strip and solder or slide alongside the seated pin.

Option 2: Use a new-style console cable and a male-male gender-changer for the DB-9. Cut off the RJ-45 from the console cable and crimp a new one on with the pins facing the opposite way (undo the rollover).


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