In its hardware manuals, Cisco variously calls its 3G RSVD port a “Diagnostic Port” or
a “3G mini-USB diagnostic port”.
In design electronics, RSVD is used to designate a reserved resource. So the 3G RSVD port is considered a RESERVED port, used to check and monitor the health of internal 3G modems.
According to a certificate of Industrial IT Certification (for its approved use in Sweden) the Cisco 819 3G RSVD port is a “Mini-USB port to support remote 3G diagnostics and monitoring tools.”
A 3G RSVD port can appear in various forms, such as:
- a mini-USB port on the rear of routers like the Cisco 819.
- a mini-USB port on the front of many 3G EHWICs, or
- as an RJ-45 console port on the faceplate of some EHWIC 3G-EVDOs devices
(where it is labelled as a “Diag Port” not an "3G RSVD" port)
It is important to note that on devices labelled “Diag Port” the cable used to connect the PC/laptop running the software diagnostic tool is the standard Cisco router console cable (RJ-45 to DB-9).
There are other slight labelling variations too. For example, a “4G” was magically added to the label of newer
3G/4G RSVD mini-USB ports on optional EHWIC cards that can be used in rack-mounted integrated service routers (like the Cisco 2901).
There is usually a Sierra Wireless AirPrime modem module attached to the back of the 3G RSVD port. Internally, the Diagnostic Port (or DM port) provides access to the debug port of the Sierra Wireless modem. Cisco’s software configuration documentation is not consistent with its naming of the 3G RSVD, and mostly it refers to an RSVD as a “DM port”. DM is likely to be an industry term meaning “Diagnostic Manager” but don’t quote me.
By connecting an industry-standard diagnostic management tool like the older Qualcomm CAIT/QXDM or the more used Spirent Universal Diagnostic Monitor (UDM) to the DM port, you can perform radio-level diagnostics and traffic monitoring on the Sierra Wireless 3G module.
Qualcomm’s eXtensible Diagnostics Manager is an expandable technology for doing things like logging
over-the-air signal messages, analysing status and performance statistics, collecting GPS/Dead Reckoning position or location data, etc.
This is because 3G is at its heart is a mobile technology.
The Spirent UDM allows developers, field and drive test teams, certification test teams and service providers the ability to monitor and analyse the performance of CDMA and EV-DO mobile devices, and to monitor network performance and traffic.
See: http://actt.co.kr/new_actt/product/pdf/spirent/UDMV2.pdf
Cisco recommends you use the following test commands to enable/disable their DM port:
router# test cell-hwic 0/1/0 dm-port local {on | off |speed}
router# test cell-hwic 0/1/0 dm-port remote {on | off}
For example, to enable the DM port, use one of these commands:
router# test cell-hwic 0/1/0 dm-port local on
router# test cell-hwic 0/1/0 dm-port remote on
Note: to enable test commands, you must first enter the “service internal” command in global configuration mode.
