Reverse telnet failing/hangin on ...Open

[joshbgosh10592]

Hello all,

I've been searching around the Internet and many forums to try to get reverse telnet working to connect a 3640 Router to a 3550 Switch.

What I know for sure is I need a rollover cable, 8-1, 7-2, etc connected to the router's AUX and the switch's con ports. That is done.

I know that I need to have the aux port on the router configured for:

line aux 0

modem InOut

transport input all

transport output all

Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
* 0 CTY - - - - - 0 0 0/0 -
129 AUX 9600/9600 - inout - - - 0 0 0/0 -
130 VTY - - - - - 1 0 0/0 -
131 VTY - - - - - 0 0 0/0 -
132 VTY - - - - - 0 0 0/0 -
133 VTY - - - - - 0 0 0/0 -
134 VTY - - - - - 0 0 0/0 -

The weird thing is, when I get into line aux 0, nothing ever updates in show run... When I try to "no line aux 0" or even to default it, I receive "% Vty line 129 doesn't exist". To make the changes to run config, I've had to go into config t> line 129, which is atleast the line for AUX 0. When changing the config for line 129, the running config for line aux 0 does reflect.

When doing a show run:
line aux 0
modem InOut
no exec (I read that having exec on causes problems.
transport input all
transport output all

To connect, I'm trying "telnet 192.168.0.1 2129) 192.168.0.1 is my loopback. My LAN is on a 10.9.x.x\16 scheme.
I'm returned with:

BurgerRouter#telnet 192.168.0.1 2129
Trying 192.168.0.1, 2129 ... Open

And then the line freeze and cannot be cleared unless I connect to it using the other means (for example, if I start the telnet to switch from Console, I have to telnet into it to run a clear line 129, which then freeze up the other console).

What are your thoughts?

[Richard Bradfield]

Connection refused is better

Please do a "Clear line Aux 0" and try again

[joshbgosh10592]

Well, same thing... Ran a clear line aux 0, hung after I hit enter after entering my password. Also tried port 2001, refused by remote host.

I'm guessing the config look fine?

Thanks again for sticking with me through this. This has been bugging me..

[will]

I'm having a similar issue and have checked everything in an isolated fashion. not sure what the answer is, but it seems the aux port is flaky, or maybe AAA might be interfering with the process in some way

[liviu.gheorghe]

Hello @will , @joshbgosh10592 ,

older routers have a default of 2 stopbits on console and AUX lines. Here is the parameters from my 2651XM for the AUX line:

TS#sho line aux 0
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
65 AUX 9600/9600 - - - - - 0 0 0/0 -

Line 65, Location: "", Type: ""
Length: 24 lines, Width: 80 columns
Baud rate (TX/RX) is 9600/9600, no parity, 2 stopbits, 8 databits
Status: Ready, Modem Signals Polled

Make sure your AUX line on the router and CON line on the switch have the same stopbits setting. The switches usually have 1 stopbit by default:

SW_EVO_PROD#sho line con 0
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
0 CTY - - - - - 0 2164 0/0 -

Line 0, Location: "", Type: ""
Length: 24 lines, Width: 80 columns
Baud rate (TX/RX) is 9600/9600, no parity, 1 stopbits, 8 databits
Status: Ready
Capabilities: none
Modem state: Ready

Adjust them to be the same with the line command:

line aux 0

 stopbits 1

Hope this helps.

[will]

hi liviu, thx for the information. in this case, it worked when i connected from SSH : 2001 to the routers aux port, but not when i used telnet. i believe the 4331 (aux port) and the 2911 (console port) had default stopbits of 1, but i will check when i get back into office. this just seemed to be some sort of flaky software or possible noise on the line. noise level was 3. seemed like I was battling ghosts on one or the other routers though.

[liviu.gheorghe]

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@will wrote:

hi liviu, thx for the information. in this case, it worked when i connected from SSH : 2001 to the routers aux port, but not when i used telnet.

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If it worked using SSH, it should work using telnet as well. Check for access-list denying telnet and allowing ssh.