Geeks With Blogs
Richard Bedwell

So I am a Network Engineer, and something that has always been troubling me is this concept of Reverse Telnet.

The theory is that from a router that you can connect to, you can use the aux port of that router to connect or "Telnet" into another router or devices' console port.

Pretty simple concept, however everyone and their brother posts and says for this to work you need a straight thru cable... (568A, or 568B cat 5, 5e, or 6)

Pretty simple concept... I know... but what these idgits seem to have gotten wrong, is that you don't use a straight thru cable, or a cross over cable, or even a rollover cable, you use an ethernet rollover cable, basically a rolled over straight thru cable.



Once you do that configuration is simple....


         Straight Thru  (B)                                 Cross over           

S1   o/w-o-g/w-b-b/w-g-br/w-br      o/w-o-g/w-b-b/w-g-br/w-br 

S2   o/w-o-g/w-b-b/w-g-br/w-br      g/w-g-o/w-b-b/w-o-br/w-br   


                          Rollover                              Ether Rollover

S1    o/w-o-g/w-g-b/w-b-br/w-br      o/w-o-g/w-b-b/w-g-br/w-br

S2    br-br/w-b-b/w-g-g/w-o-o/w      br-br/w-g-b/w-b-g/w-o-o/w

on cisco devices you go into the Line Aux0 and configure modem inout. Then check line numbers, you'll see a line associated with Aux 0, usually on newer routers this is 1, add 2000 to that and you have your port number....

Once you figure out the port number of your line simply connect the cable, and telnet to the lo0 using that port number.... Simple...

Posted on Wednesday, March 3, 2010 12:53 PM Technical Musings | Back to top

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