How to configure Cisco IOS Banners

This topic is to discuss the following lesson:

Hello Rene

I’m using DIGI PortServer II 16 with SecureCRT, but when I click on connect to open my rack session, there is a black screen with nothing I have to press enter to start the session, is this normal ?

Thanks a lot
Soufiane

Hello Rene !

I didn´t understood the command “telnet 1.1.1.1 6097” -> why 6097 ? what this means ?

Thanks !

Hi Rodrigo,

This is the destination port. Telnet uses TCP port 23 so if you don’t specify a port number, it will use TCP 23.

You can connect to different port numbers to see if a service is responding or not. I like using it to connect to HTTP (80), HTTPS (443) or in this case, 6097.

Rene

Hi Rene,
I cant understand the Reverse Telnet that you have describe in last section. Why we need it/what is the uses of it and how its works. From where we get the IP(1.1.1.1) and port(6097) . Thx

br//
zaman

Hello Mohammad

In order to save space Rene didn’t explain extensively how to configure reverse telnet, but just showed how to configure a banner for it. A nice piece of information about reverse telnet can be found at this Cisco support forum article, but I can tell you a little about it here.

It basically gives you the ability to telnet into a network connected device (say a router) and then connect to a neighbouring device via its console connection. In essence, this gives you the opportunity to remotely connect to the console connection of a device. This can be useful when IP connectivity has been lost to a device and you are far away from the device itself (in a different city or country for example).

The IP address 1.1.1.1 is a loopback interface that has to be configured on the device and the port used is 6000 + TTY number of the AUX: 6000+97 = 6097. The 6000 may be 2000 or another number depending on the platform you use. You can find out more about it in the link above.

I hope this has been helpful!

Laz

Here’s an example of a Cisco terminal server where we use reverse telnet:

https://networklessons.com/cisco/ccie-routing-switching/cisco-terminal-server-configuration-example/

Hi Rene,

I am confused about the cable connection between two device. Which type of cable have to be used on AUX port end and Console end if I dont have NM16-A or NM32-A Module or Cisco 2511-RJ.Please help me to understand .Thx

br/zaman

Hello Mohammad.

If you are using the AUX port from one device to the console port of the other (not a terminal server connection as in the example shown by @ReneMolenaar), then you just need a normal straight through cable, that is, a normal patch cable. Both AUX and CONSOLE ports have RJ-45 connectors, so both ends of the cable must be RJ-45. Note that a normal patch cable may have different Pinouts for the colours depending on the standard being used (T568A or T568B) but each pin on each end is the same wire, and that is the basic definition of a straight through cable.

I hope this has been helpful!

Laz

Hi Laz,
I have tried your describe way but can’t connect …My setup is …
I have a online router(Name DHAKA) that’s loopback is reachable from internet .Now connect this router(DHAKA) AUX port to another router(Name KHULNA) console port using straight through(T568B used) cable and Telnet to loopback of DHAKA Router and configured the aux port like …

DHAKA#config t
DHAKA(config)#line aux 0
DHAKA(config-line)#modem InOut
DHAKA(config-line)#transport input all
DHAKA(config-line)#speed 19200
DHAKA(config-line)#exit
and check the line of Aux port ....
DHAKA# sh line
 Tty Typ     Tx/Rx    A Modem  Roty AccO AccI   Uses   Noise  Overruns   Int
      0 CTY              -    -      -    -    -      0       0     0/0       -
      **5 AUX  19200/19200 - inout     -    -    -      7       0     0/0**       -
*     6 VTY              -    -      -    -    - 101226       0     0/0    

And telnet from the DHAKA Router with correct port …

DHAKA# telnet ( The loopback is reachable from internet) 2005

but I cannt connect to KHULNA Router …Please help me to understand the issue .Thx

br//zaman

Hi Zaman,

It should work like this. First, check the AUX line:

R1#show line
   Tty Line Typ     Tx/Rx    A Modem  Roty AccO AccI  Uses  Noise Overruns  Int
*     0    0 CTY              -    -      -    -    -     0      0    0/0      -
      1    1 AUX   9600/9600  -    -      -    -    -     0      0    0/0      -
    514  514 VTY              -    -      -    -    -     0      0    0/0      -
    515  515 VTY              -    -      -    -    -     0      0    0/0      -
    516  516 VTY              -    -      -    -    -     0      0    0/0      -
    517  517 VTY              -    -      -    -    -     0      0    0/0      -
    518  518 VTY              -    -      -    -    -     0      0    0/0      -

The AUX on my router is #1. The only thing you should have to do is configure the AUX line like this:

R1(config)#line aux 0  
R1(config-line)#transport input telnet

Once you are connected to this router, access the AUX line with the correct line number. It starts with 2000 so in my case it’s 2001:

R1#telnet 1.1.1.1 2001
Trying 1.1.1.1, 2001 ... Open

Just to be sure, the cable has to be a rollover cable. It’s wired like this:

<img src="/uploads/default/original/1X/19f58020435a7add95abece76fb2db0b3e30974a.jpg" width="400"height=“300”>

Here’s a picture of a cable I created yesterday: