console vs telnet

[iamtheone12345]

Hi guys,

Okay this question may sound silly but i am having some problem.

I work as a VPN admin in a company and understandibly i am not so good in routing and switching.

I know that console access is physical access to a device and telnet is remote access to a device.

But it seems that we can telnet to the console port of a device.

Syntax: telnet       console ip address      console port

I sometimes Telnet to the console port using the above syntax  if i do not have GUI access to the VPN box.

What i am not understanding is how are we actually telnetting on to the console?Isn't console access supposed to be

physical rather than remote?

I have been already working 6 months in the company and i am to shy to ask anyone this question.As they may think that

I am totally useless.

I hope somebody can shed some light on it.

[John Blakley]

Is this a router? Can you post your line con 0 config?

[iamtheone12345]

I am talking about a VPN box.Ofcourse it could be any network device...switch ,routers.

My question is how do you configure a console port of a network device so that you can telnet to that console port?

[Reza Sharifi · Accepted solution]

You can't telnet to the console, but you can use a terminal server and use reverse telnet

http://www.cisco.com/en/US/docs/ios/12_0/dial/configuration/guide/dcrtelnt.html

HTH

[yogaville · Accepted solution]

To put it in laymans terms you are not actually consoling to the device itself. The IP adress you are using is for the terminal server. The device is connected to the port you specify in the telnet command. That is where the physical connection lies. From that port on the term server a cable goes to the router/vpn/switch console port. Good luck.

[Ven Taylor · Accepted solution]

You may want to look at your physical layout.

That command syntax is used to console into a device via a terminal server.

If you telnet to the IP address by itself (without the port) you'll see you're in the terminal server.

The terminal server has "ports numbers" like 2001-2015 that represent physical ports 1-15.

These physical ports have serial cables connected to them that can be plugged into the console ports of a number of devices.

Depending on how many terminal servers you own, and how creative your cabling, you can use a terminal server to connect to the console port of every Cisco box you own.

Ven

[iamtheone12345]

Hi reza,computer support and Ven,

Thank you for  your time and replying to my post.

As far as i am understanding,i am actually connecting to a terminal server which has a serial connection with the

VPN box console port.

As per your sugesstion i have logged into the terminal server by just telnetting on to the Ip address of the Terminal server.

Now is there any way to know which devices console ports are connected to this terminal server?

Say in my case the console port is 2055 for example.

My objective is to see the terminal server is connected to the VPN box .

I have executed the following commands on the terminal server:

1)Show cdp nei detail (i could see a switch/bridge connected to it)

2)show ip int brief

3)show int desc

But i am not seeing anything that suggests that the VPN box is connected to it?

You all have been very helpfull.

[Ven Taylor · Accepted solution]

Unfortunately, no.

The console port will not send or receive cdp.

The only way to know for sure is to gain physical access to it and trace the cable from the port.

Sounds like it's a big terminal server, so your question isn't a stupid one.

I'd say ask someone.  Terminal server connections, if not properly documented, are near impossible to figure out.

Ven

[iamtheone12345]

Thank you Ven.

I executed a sh port status on the terminal server.

It gave me so many ports that i gave up.

You were right about the big terminal server.The CLIENT i work for has the 4th largest network infrastucture in the world.

Thanks again.....i will contact the onsite team.I just wanted to maka sure that i dont ask them anything stuoid.