2.1 Modem Functions
2.1.7 Connections specific to Cisco products
The auxiliary and console ports are configured as DTE devices on Cisco access servers. Terminals are also DTE devices. As noted earlier, two DTE devices cannot be directly connected unless the signals are rolled exactly once, so you must roll the pins either in the cable or in the DB-25 adapters, but not both. The formula for a successful DTE-to-DTE connection is one of the following:
  • DTE to a rolled RJ-45 cable to a straight DB-25 adapter to DTE
  • DTE to a straight RJ-45 cable to a rolled DB-25 adapter to DTE

When connecting a DTE to a DCE, however, you should have either no rolls, or two rolls in the cable and the connector. The formula for a successful DTE-to-DCE connection is one of the following:

  • DTE to a rolled RJ-45 cable to a rolled DB-25 adapter to DCE
  • DTE to a straight RJ-45 cable to a straight DB-25 adapter to DCE

Figure shows some possible working connections between an access server and various types of end devices.

NOTE: CISCO specific cable ordering information. The part number for the rolled RJ-45-to-RJ-45 cable is CAB-500RJ. When you order access servers with async ports, you need to order the corresponding cable accessories. Order one CAB-OCTAL-KIT (eight-lead octal cable and eight male DB-25 modem connectors) for each 68-pin async connector that you have on the access server. If the modem uses an RJ-45 connector, you can order one CAB-OCTAL-ASYNC (a rolled eight-lead octal cable with RJ-45 connectors); special adapters might be required. Connecting a modem to the console port of a router is a security risk because it initially has no protection or security features enabled.

Cisco routers ship with a console and auxiliary port cabling kit that includes the following components:

  • RJ-45-to-RJ-45 rolled cable
  • RJ-45-to-DB-9 female DTE adapter (labeled TERMINAL)-typically used to connect to a PC being used as a console terminal
  • RJ-45-to-DB-25 female DTE adapter (labeled TERMINAL)-used to connect a terminal to the console or auxiliary port
  • RJ-45-to-DB-25 male DCE adapter (labeled MODEM)-used to connect the auxiliary port to a modem

Table presents the port types for console and auxiliary ports on Cisco routers and switches.