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ASR 920 series routers console port

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 Hello Everyone,

 

I am a 20+-year veteran user of Cisco routers and switches but I am fairly new to the ASR 920 series. Recently, I purchased 4 asr920’s for a specialized project. Imagine my surprise when I went to set them up and found that the console port was USB only! Well, no big deal. Since I have hundreds of console cables lying around, I did not order one in this purchase. So, I followed the instructions in the installation manual. I found a type-a   -to-  type-a cable and connected my laptop. I downloaded Cisco’s ‘driver’ and installed it.No good. It did not work. I uninstalled and re-installed a few times but still nothing. I grabbed another computer and tried it. I also got another cable. Still nothing.

 

I google-researched the issue and learned that, low and behold, the ‘USB’ port is not USB at all, but is plain old rs232. Some dummy (fire this guy!) decided to get creative and use a USB chassis connector for the rs232 serial port. Since I had an immediate need, I researched the pin-outs of the connectors and systems involved. I took a usb cable and cut one end off. The I got a light-blue Cisco console cable and cut the RJ45 end off. I then spliced the two cut ends together. After fiddling with it for a few minutes I had it working. I was able to get ip addresses on each of my four routers and get them connected to my lab network for further configuration.

 

Now I won’t go into why they would use a usb connector for an rs232 port, or why the installation guide says to connect it to your pc usb port or why they have you install a driver when it is not needed….  Those are thoughts for another day. My purpose here is to share with everyone a simple way to make yourself a console cable for the asr920 that will work and is a bit more elegant than my ‘McGiver’ cable.

 

The easiest thing to do is take a usb cable, cut one end off, and crimp on a RJ45 mod plug. With this cable, one can then use a cheapo RJ45 inline coupler to couple this new cable to the end of a ‘standard’ Cisco console cable. If you don’t have a crimp tool, then you could simply use a biscuit jack on the end of the usb cable instead of the modular plug.

 

Now bear in mind that most usb cables have a wire color standard but I’m sure there are some out there that use different colors. The color doesn’t really matter; it is what wire connects to what pin that is important. It is advisable to use an ohmmeter to verify the pin-out if necessary.

 

The correct cable pin-out is shown below. Just connect a mod plug on the end of a usb cable, couple this with a regular console cable and you’ll be in business!!

 

usb                                             8-pos mod plug

cable pin#                                   (rj45 pin #)

---                                                ---------------------

1              red (+5v)                           2

2              white (data-)                     3

3              green (data+)                    6

4              black (ground)                   4

 

Regards,

-Chuck Wilson

Comments
Beginner

There should be four "USB" ports. Two RS-232 in disguise, as you have described, and two actual USB ports. The ones near the environmental sensor RJ-45  (or below?) are the ones you want, not the ones near the mgmt ethernet port, confusingly enough. One's' for thumb drives and the other is the console port with built in uart.

Beginner

Thank you very much for this information, I was not able to find it anywhere else :)

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