Dialer profile: Connection exists but no telnet session possible

mfg_toobi · ‎07-12-2012

Hey everyone!

I have a big problem with my Cisco 1841 and the WIC-1AM-V2 in Slot 0.

I got the task, to test if it is possible, to build up a connection (Dial on Demand Routing) to a remote modem, which is connected to a console port of another Cisco 1841, with the integrated modem card over POTS from the CLI of the router. My router will only dial out to the remote modems and only if its needed.

I am connected to the router with the integrated modem card over a console cable on the console port. The remote modem is also connected to the console port of the remote Cisco 1841.

I found out, with my Dialer Profile configuration, it is possible to build up a connection. I configured a dialer list, that specifies that all ip traffic is permitted an interesting for my dialer interface. So a telnet or ping brings up my dialer, which brings up my Async interface. With the "show line" command, I can see that the TTY line, connected with the Async0/0/0 Interface is in use for 5 minutes, because of the "exec-timeout 5 0", which is configured on the remote router.

Now the problem is, in this 5 minutes, I can not use a remote telnet on this line with my loopback interface, because the line is already in use and I get a "connection refused". The first telnet I use runs in a timeout, because the remote host is not responding. When I dial out directly from the modem card and not from the CLI with the AT-commands, I get also the connection and with a return i get the login prompt.

I will post my actual config, so that you can see maybe a mistake I did or which command I must use, to get a working connection.

Current configuration : 3181 bytes

!

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

service linenumber

!

hostname oob-test

!

boot-start-marker

boot-end-marker

!

logging buffered 8182 debugging

enable secret 5 $1$C61o$uwI8KVOlYVtAhVpc7Sj3U0

!

no aaa new-model

ip cef

!

ip auth-proxy max-nodata-conns 3

ip admission max-nodata-conns 3

!

ip host gelnlxxx 10.200.45.27

ip host gelitxxx 10.200.45.17

ip host geldexxx 10.200.45.69

!

chat-script gelitxxx ABORT ERROR "" "ATX3" OK "ATDT000xxxxxxx" TIMEOUT 120 CONNECT \r

chat-script gelnlxxx ABORT ERROR "" "ATX3" OK "ATDT000xxxxxxx" TIMEOUT 120 CONNECT \r

chat-script geldexxx ABORT ERROR "" "ATX3" OK "ATDT00xxxxxxx" TIMEOUT 120 CONNECT \r

!

ip telnet timeout retransmit 120

!

interface Loopback99

ip address 10.200.45.245 255.255.255.255

!

interface FastEthernet0/0

no ip address

shutdown

duplex auto

speed auto

!

interface FastEthernet0/1

ip address 192.168.0.1 255.255.255.0

shutdown

duplex auto

speed auto

!

interface Async0/0/0

ip unnumbered Loopback99

encapsulation slip

dialer in-band

dialer pool-member 1

async mode interactive

no peer default ip address

routing dynamic

!

interface Dialer1

ip address 7.7.7.7 255.255.255.0

dialer pool 1

dialer remote-name gelnlxxx

dialer idle-timeout 300

dialer string 000xxxxxxx modem-script gelnlxxx

dialer-group 11

!

interface Dialer2

ip unnumbered Loopback99

dialer pool 1

dialer remote-name gelitxxx

dialer idle-timeout 300

dialer string 000xxxxxxxx modem-script gelitxxx

dialer-group 11

!

interface Dialer3

ip unnumbered Loopback99

dialer pool 1

dialer remote-name geldexxx

dialer idle-timeout 300

dialer string 00xxxxx modem-script geldexxx

dialer-group 11

!

ip forward-protocol nd

ip route 10.200.45.17 255.255.255.255 Dialer2

ip route 10.200.45.27 255.255.255.255 Dialer1

ip route 10.200.45.69 255.255.255.255 Dialer3

!

ip http server

no ip http secure-server

!

dialer-list 11 protocol ip permit

!

control-plane

!

alias exec gelnlxxx telnet 10.200.45.27 2002

alias exec gelitxxx telnet 10.200.45.17 2002 /source-interface Dialer2

alias exec geldexxx telnet 10.200.45.69 /source-interface Dialer3

!

line con 0

exec-timeout 5 0

transport output all

line aux 0

line 0/0/0

exec-timeout 30 0

session-limit 3

modem InOut

modem autoconfigure discovery

transport input all

transport output all

stopbits 1

speed 115200

flowcontrol hardware

line vty 0 4

exec-timeout 30 0

logging synchronous

login local

history size 256

transport input all

transport output all

!

scheduler allocate 20000 1000

end

I hope you can give me a hint. If you have any questions, don´t hesitate to ask.

paolo bevilacqua · ‎07-12-2012

Start checking that you can ping before telnet.

mfg_toobi · ‎07-12-2012

Dear Paolo,

I tried to ping the ip address of the remote router, but I got only ............... Maybe I am pinging the wrong ip address. When I build up a connection to the remote router via POTS and modem card from the CLI of my router, which IP of the remote router should I ping? The ip address which I used was the Loopback IP of the remote router. For example, the Loopback Ip of the remote router is 10.200.45.27 255.255.255.255. Must the Dialer or Async interface be in the same subnet to get a working ping?

paolo bevilacqua · ‎07-12-2012

255.255.255.255. Must the Dialer or Async interface be in the same subnet to get a working ping?

Yes, otherwise you have to setup some static routes etc.

Note however that IP over dial-up modem is too slow for almost any practical purpose, generally modems are used only for out of band management.

mfg_toobi · ‎07-13-2012

Dear Paolo,

you are right with the out of band management. This is the aim of my project. Maybe I was thinking in the wrong direction (using DDR). I am not trying to route anything, I am just trying to manage remote routers via POTS connection. Please have a look at the attachment (topology-setup). There you can see my described setup, which we have in the moment.

The aim is to get the CLI of the Branch-router to my HQ-router. When I start my chat-scripts, the dial connection works fine for 5 minutes, but I don´t get the CLI of the Branch-router to my HQ-router. But when I do a reverse Telnet (Loopback99 IP + Port of Async line) I get on the modem card (WIC-1AM-V2) and there I get the CLI of the Branch-router using the needed AT-Commands (atx3 and atdtxxx).

Now I am looking for a possibility, to get the CLI of the Branch-router to my HQ-router, from the CLI of my HQ-router.

paolo bevilacqua · ‎07-13-2012

You can then remove all the async and dialer commands.

If you can configure a chat script that dials automatically that's good otherwise just do manually.

There are also virtual com drivers to use the modem in HQ with a terminal program like Putty or Kitty

Please remember to rate useful posts clicking on the stars below.

mfg_toobi · ‎07-13-2012

Thank you for the advice, I will try it out! I also rated your answer is you wished.

If you can configure a chat script that dials automatically that's good otherwise just do manually.

I have configured a chat script, which calls the remote site:

chat-script gelitxxx ABORT ERROR "" "ATX3" OK "ATDT000xxxxxxx" TIMEOUT 120 CONNECT \r

But once the call is active, how do I get the incoming characters from the remote router to my command line?

There are also virtual com drivers to use the modem in HQ with a terminal program like Putty or Kitt

Can you give me a link or another hint, what you mean exactly with this virtual com drivers?

The HQ-router shall be used as a "management-server" for multiple engineers.