David’s Cisco Networking Blog

Oct 19 2007   3:42PM GMT

What is a Cisco console cable?

David Davis David Davis Profile: David Davis

Say that you take a new Cisco router, switch, or firewall out of the box and hook it up. Does it work? No. It isn’t like a Linksys or Netgear router. It has no DHCP or anything like that. It has to be configured first.

How do you configure it? You have to connect to the console port, like this console port on a Cisco 1800 series router:

Cisco Console port

But what to connect to it? No, don’t use an Ethernet cable – it won’t work. This is a SERIAL port that needs to go to the serial/COM port on your PC or laptop (if you still have one). What what you need is a ROLLED cable. Here is what it looks like:

Rolled Cable

Cisco also has a good picture of one, below….

Cisco Rolled Cable

However, how are you going to get that rolled cable connected to your PC? Don’t plug it into the Ethernet port! Remember, it is a Serial Cable. You need to connect it to the 9 PIN serial port on your PC (hopefully you have one but I will tell you what to do if you don’t in a minute. To connect it, you need to convert the RJ45 end to Serial with an adaptor, like this:Console Adaptor

Many times, these came with routers or were sold in a package alone with the rolled cable, like this:

Older Cisco Console Cable

Today, the DB9 to RJ45 converter is coming molded to the console cable, like this:

Newer Cisco Console cable

Once you have the router, switch, or firewall physicall connected with the right cable & adaptor, you need to use your terminal emulator to communicate with the console port. For more information on that topic, I recommend this article on how to use Hyperterminal to connect to your Cisco router.

All the best to you,
David Davis, CCIE, VCP, CISSP

Personal Website: HappyRouter.com – home of Cisco how-to articles & videos
David Recommends:
HappyRouter Cisco VMware Workstation & Server Video Training Series
HappyRouter Cisco CCNA & CCNP Video Training Series

6  Comments on this Post

 
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  • Makeeley
    Hi David Just a quick point. Above you mention that you connect the DB9 adapter to the COM port on your PC or laptop and you mentioned that you would tell people how to get around the issue of their laptop not having a COM port later, but you never did. Now I am quite sure that the majority if not all the people reading this will be aware of the fact that you can get a USB to DB9 adapter cable, but just for completeness and for anybody new to IT networking I thought I would mention it. Also, a handy bit on information for if you ever find yourself in the position of having access to one of the DB9-RJ45 adapters shown above but no rollover cable. The cable layout of these adapters is as follows Pin 1 -- Blue wire Pin 2 -- Orange wire Pin 3 -- Black wire Pin 4 -- Red wire Pin 5 -- Green wire Pin 6 -- Yellow wire Pin 7 -- Brown wire Pin 8 -- Grey/White wire So if you wire the DB9-RJ45 adapter as follows you can use it with a CAT5 straight cable to gain console access to Cisco equipment. The adapter should have a female DB9 interface. Blue cable to position 8 Orange cable to position 6 Black cable to position 2 Yellow cable to position 3 Brown cable to position 4 Grey/white cable to position 7 Red and green cables spliced together to position 5 To splice the red and green cables together, remove the small brass pin from one of the cables and bare a little of the wire. Carefully remove a small amount of the outer plastic covering of the other cable to bare the wire. Join the bare wires from each cable together and secure with insulation tape. Having this information has helped me on a few occasions. Best Regards, Michael
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  • David Davis
    Excellent comment Makeeley, THANKS! -David
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  • GC
    So, I have a rolled cat 5 cable, but don't have a com port..... Is there an RJ-45-USB adapter?
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  • Brockstedt
    Excellent post. I do have a question in regards to pinout configuration. Is there a pinout for connecting a Cisco molded rollover cable to a DB-9/RJ-45 connector that is connected to a DIGI PortServer TS 16 Rack RJ-45 switchport via cat5 cable.
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  • Merlo
    can someone tell me what is a console cable please?
    I mean what definition can be given to it, not what it is use for or how to get it.
    Thanks!!!
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  • dzidududzidudu
    This site made this look so simple.
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