Piedinature - Pinouts
Cisco Auxiliary Port for Cisco 1000, 1600, 2500, 2600, And 3600 Series Routers

Reference and Sources:

The auxiliary port is configured as data terminal equipment (DTE).

(RJ45 FEMALE CONNECTOR at the Cisco routers)

(RJ45 MALE CONNECTOR at the cables)

Pin	Name	Description	Dir
1	RTS	Request To Send	OUT
2	DTR	Data Terminal Ready	OUT
3	TXD	Tranceive Data	OUT
4	GND	Ground	-
5	GND	Ground	-
6	RXD	Receive Data	IN
7	DSR	Data Set Ready	IN
8	CTS	Clear To Send	IN

Piedinature - PinoutsCisco Auxiliary Port for Cisco 1000, 1600, 2500, 2600, And 3600 Series Routers