The vi editor - Lesson 1

We mostly use VI editor in our office while editing different sort of scripts. I cam across a very interesting tutorial regarding VI editor in Linux. I hereby present it for your viewing pleasure and learning as well :)

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Difference between rollover cable or crossover cable used to connect to router's console port?

08-Jul-2011 20:45

jvd

4 posts since
22-Oct-2010

While studying for ICND1 I came to know tht ,

A cross over cable is used to connect to like devices  (similar devices)

Rollover cable (also known as Cisco console cable) is a type of  cable that is most commonly used to connect a computer terminal to a router's console port.

So it is said tht when u  connect Pc to a console port of router  -> Cross over cable is used.

It same in the case of rollover cable  which is used to connect Pc to a console port of router..

If so then when and why is roll over cable is used to connect PC to a console port of router...and so how can we  answer a drag and drop question which gives both options and select the cable for PC to router console port.

Categories: CCNA Tags: cabling, and, over, roll, cross

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  Scott Morris - CCDE/4xCCIE/2xJNCIE

  8,269 posts since
  07-Oct-2008

  1. 08-Jul-2011 20:55 (in response to jvd)

  Re: Difference between rollover cable or crossover cable used to connect to router's console port?

  Crossover is something that crosses transmit and receive pairs of a cable.  Like in ethernet, or a serial cable (little more complicated!).  In ethernet, pairs 1-2 cross with 3-6 on opposite ends of the cable crossing the TX/RX pairs.  With a T1, it's 1-2 and 4-5 pairs.

  
  

  A rollover cable simply has 1,2,3,4,5,6,7,8 on one side and 8,7,6,5,4,3,2,1 on the other side.  It needs additional pieces (the DB-9 to RJ45 converters) to make it a null-modem cable (which is technically different than a crossover serial cable, but likely going to get into WAY too much detail to care about right now in your learning!)

  
  

  HTH,

  
  

  Scott

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  jvd

  4 posts since
  22-Oct-2010

  2. 08-Jul-2011 21:40 (in response to Scott Morris - CCDE/4xCCIE/2xJNCIE)

  Re: Difference between rollover cable or crossover cable used to connect to router's console port?

  Ok Scott i understood the concept u explained i thank u for tht . But my doubt is whtr which of this cable is commonly to connect pc to router whtr its crossover or rollover....

  I hope ur answer is Cross over , then which case do we use rollover to connect Pc to a router...Is rollover used when our pc don't have a serial port (com port) and we use usb converter to connect to db-9...

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  Scott Morris - CCDE/4xCCIE/2xJNCIE

  8,269 posts since
  07-Oct-2008

  3. 08-Jul-2011 21:57 (in response to jvd)

  Re: Difference between rollover cable or crossover cable used to connect to router's console port?

  Well, that's the tricky part....

  
  

  Yes, they both will connect a PC to a router.  But for what purpose is the important part!

  
  

  crossover cable (ethernet) will connect the PC to the router's ethernet port and will therefore allow network communications (packets)

  
  

  rollover cable (serial) will connect the PC to the router's console port and will therefore allow terminal communications (null modem = dumb terminal)

  
  

  These days you'd likely need a USB to Serial adapter to get anything resembling a DB-9 connector on your PC.  Then you'll need the DB9 to RJ-45 adapter to plug your rollover cable into.

  
  

  The rollover part still needs a serial port (or usb to serial), but it's used to convert a standard serial cable (like a modem uses) into a null-modem cable for direct or dumb-terminal communications.

  
  

  Your USB is merely today's representation of a serial connector.  WAY back when it was a DB-25, then most things became DB-9.  Now it's USB.  In the end it's still a serial bus though!  Just different pinouts and other festive details!

  
  

  HTH,

  
  

  Scott

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  jvd

  4 posts since
  22-Oct-2010

  4. 08-Jul-2011 22:08 (in response to Scott Morris - CCDE/4xCCIE/2xJNCIE)

  Re: Difference between rollover cable or crossover cable used to connect to router's console port?

  Thank You Scott Morris for ur detailed and informative explanation to clarify my doubts....and tht too from a VIP like u is really appreciated... 

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  Scott Morris - CCDE/4xCCIE/2xJNCIE

  8,269 posts since
  07-Oct-2008

  5. 09-Jul-2011 07:08 (in response to jvd)

  Re: Difference between rollover cable or crossover cable used to connect to router's console port?

  Any time....   And I'm just a normal guy, but thanks!  

  
  

  Scott