Cisco RJ45 to DB25

Pinout of the Cisco RJ-45 to DB-25 rollover console adapter, mapping the 8-pin RJ-45 console port to DB-25 DTE, DCE, and modem configurations.

Updated:

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RJ45 MALE CONNECTOR RJ45 MALE CONNECTOR To the Cisco router

The Cisco RJ-45 console and AUX ports carry asynchronous RS-232 (EIA/TIA-232) signals over an 8-pin RJ-45 connector wired as DTE. A rolled (rollover) cable reverses all eight conductors end-to-end, and a plug-in adapter then converts the RJ-45 to a DB-25 socket on the terminal or PC side. Two adapter variants exist: the DTE adapter (labelled “Terminal,” Cisco part 29-0810-01 / CFDTE) for connecting to a terminal or PC serial port, and the modem adapter (labelled “Modem,” MMOD) for connecting to DCE modem equipment; pin mappings differ between the two. Default console settings are 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control.

AdapterDTE M/F Pins1DCE M/F PinsMMOD Pins2
RJ-45 PinsDB-25 Pins
1455
22068
3233
4777
5777
6322
762020
8544

Notes

  • (1) The FDTE RJ-45-to-DB-25 adapter is labeled “Terminal.”
  • (2) The MMOD RJ-45-to-DB-25 adapter is labeled “Modem.”
  • The Cisco console port (RJ-45 DTE) pinout: pin 1=RTS out, 2=DTR out, 3=TD out, 4=SigGnd, 5=SigGnd, 6=RD in, 7=DSR in, 8=CTS in.
  • The rollover cable (Cisco CAB-500RJ) reverses all 8 conductors: pin 1↔8, 2↔7, 3↔6, 4↔5.
  • The console port does not support hardware (RTS/CTS) flow control; the AUX port does.
  • Standard DB-25 RS-232 signal assignments: TXD=pin 2, RXD=pin 3, RTS=pin 4, CTS=pin 5, DSR=pin 6, GND=pin 7, DTR=pin 20.

Signals

  • RTS — Request To Send; output from the Cisco console port on RJ-45 pin 1.
  • DTR — Data Terminal Ready; output from the Cisco console port on RJ-45 pin 2.
  • TD — Transmit Data; serial data output from the router on RJ-45 pin 3.
  • SigGnd — Signal Ground; reference ground on RJ-45 pins 4 and 5, both mapped to DB-25 pin 7.
  • RD — Receive Data; serial data input to the router on RJ-45 pin 6.
  • DSR — Data Set Ready; input to the Cisco console port on RJ-45 pin 7.
  • CTS — Clear To Send; input to the Cisco console port on RJ-45 pin 8.

References

Category:Serial Cables