why the name "reverse" telnet

Answered Question
Aug 4th, 2007

Hi Friends,

From my understanding, a "forward telnet" session is started by a remote user who wants to remotely control a router or switch, and a "reverse telnet" session is started when the host device itself initates the telnet sessions.

What i am finding difficult to digest is why has cisco named the telnet from the device to another device as "reverse" telnet?? Any help on this answer is highly appreciated. Thanks!

Regards,

Manoj

I have this problem too.
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Correct Answer by mohammedmahmoud about 9 years 4 months ago

Hi,

Although i somehow agree with Scott, but i can find it also not that bad, plus i don't think that the name was introduced by Cisco, look it in this way:

forward telnet -> when telneting to a Cisco router from another device - Since this is the normal scenario of telneting, where you need to gain access to a Cisco router.

reverse telnet -> when telneting from a Cisco router to another device (which is the reverse of the other scenario).

HTH,

Mohammed Mahmoud.

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Overall Rating: 4.5 (2 ratings)
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scottmac Sat, 08/04/2007 - 12:29

I believe it just bols down to a poor choice of words. In most cases, you're not really even telnetting out to the other device, it's usually a serial connection (like a console).

Sometimes people use a label and, stupid or not, it sticks (like "Lightning Arrestor" which is completely useless against a lightning strike).

It is what it is. At this point it's a well-recognized term, certainly within the Cisco user/implementor community.

Good Luck

Scott

Correct Answer
mohammedmahmoud Sun, 08/05/2007 - 03:46

Hi,

Although i somehow agree with Scott, but i can find it also not that bad, plus i don't think that the name was introduced by Cisco, look it in this way:

forward telnet -> when telneting to a Cisco router from another device - Since this is the normal scenario of telneting, where you need to gain access to a Cisco router.

reverse telnet -> when telneting from a Cisco router to another device (which is the reverse of the other scenario).

HTH,

Mohammed Mahmoud.

Manoj Wadhwa Sun, 08/05/2007 - 08:13

Mohammed,

I will have to convince myself with the above explanation. Thank you for putting this forward in your own understandable way.

Cheers!!!

mohammedmahmoud Sun, 08/05/2007 - 10:42

Hi Manoj,

Well its there like this so we need to comply with it because of 2 things, first of all we won't change it (i don't live with this rule for every aspect in life :) just with some technical issues that needs to be put in ones understandable way like you've said) and above that all we have to appreciate those people who have wasted their valuable life time developing it, unless we have something better to contribute with, which i think is the aim of all of us.

BR,

Mohammed Mahmoud.

Tony.henry Mon, 08/06/2007 - 13:07

Manoj,

To be honest I've never heard of the term forward telnet. I've utilised reverse telnet many times, to communicate with modems or other devices that were remote but I needed for whatever reason to communicate with the console.

The name reverse I guess may have come from the fact that when you telnet to the reverse port of a router. You don't get the router, you get whatever is connected to the Aux port. So the router responds to the connection and sends the async text that it sees coming in the aux port

The command "show line" will show what the router sees as it's Aux port and the reverse telnet port will simply be that number plus 2000.

Hope that Helps

Tony

smothuku Tue, 08/07/2007 - 04:17

Hi Manoj ,

The term reverse Telnet means that you are initiating a Telnet session out the asynchronous line, instead of accepting a connection into the line (which is a forward connection).

While doing reverse telnet you must use port number where as for telnet no need to mention any port number.

please check the below link.

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

I never heard forward telnet...

Telnet in the sense accessing a router or switch or from one cisco device to another cisco device.

Cheers :)

Satish

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