Here's a couple of Cisco docs that helped me get things to work. One of
the big issues is getting the modem to lock its data rate on the dte
side. Some modem can be configured to lock the rate. Other you need to
set up a script on the Cisco side so the modem can learn the rate.
> -----Original Message-----
> From: tj [SMTP:tj @
elephant .
istiy .
yn .
cn]
> Sent: Monday, November 10, 1997 5:02 PM
> To: MIKE JENKINS
> Cc: firewalls @
greatcircle .
com
> Subject: help about cisco 2511 config
>
> Hi,every one here,I have two question about the cisco 2511 router:
>
> 1. I set up the speed of whole 16 async port to 115200, and turn
> on the modem autoconfig,(my modem's speed 1s 33600,),then I dial
> in use ppp, but it does not work.So I change the the speed of whole
> 16 async port to 14400,then I can get conneted.So I want to know if
> someone can tell me how to resove it or if you use cisco 2511 also,
> please send me your configuration.
> 2.I read the hand book and it said you can use reverse telnet to
> config
> your modem,like "telnet 233.233.233.1 2001" (where 233.233.233.1 is my
>
> cisco 2511's ip address ,and 2001 means the 1st async port),thus I can
>
> use the at commant to config the modem ,but now I can not ,it said "
> connect
> is refused by host".So who can tell me why and how ?
>
>
> thanks a lot.
> Tian Jun
Title: Cisco - Basic Modem Cabling and Configuration
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Basic Modem Cabling and Configuration
Introduction
This document will show you how to configure most popular modems to work
on a Cisco access server or on a router's console/AUX port. The first
section, "RS-232 Cabling," provides important background information,
but if you're already familiar with modem cabling, go ahead and skip to
the section called "Configuring the Cisco Side" on page 3.
RS-232 Cabling
The end-to-end topology for a dial-in connection looks like this:
-------- --------
|Cisco | -------- |access| ------- -------- -------- -----------
|Access|->|RS-232|->|server|->|PSTN*|->|client|->|RS-232|->|client PC|
|Server| -------- |modem | ------- |modem | -------- |or router|
-------- -------- *Public -------- -----------
Switch
Telephone
Network
The Cisco access server and the client PC or router are generally called
Data Terminal Equipment (DTE), and the server and client modems are
called Data Circuit-terminating Equipment (DCE).
To connect a modem to a Cisco 2500, or RJ-45-based console or AUX port,
use the setup below. See the faxback document "Cabling Guide for RJ-45
Console and AUX Ports" for more details.
console/AUX port----Rolled RJ-45 Cable + CAB-MMOD----Modem
To connect a modem to a Cisco 4000 or 7000, or DB-25-based AUX port, use
the setup below.
AUX Port----DB-25 Straight Cable----Modem
The Cisco access server uses three pairs of wires to connect the DCE to
the DTE. In each pair, one wire transmits, and the other receives.
These pairs are TX/RX, RTS/CTS, and DTR/DCD. Each pair requires specific
configuration on both the DTE and the DCE.
TX/RX - Data Transfer
Transmit: DTE >---TX---> DCE
Receive: DTE <---RX---< DCE
Transmit and receive speed is set on the modem using the TX/RX wire
pair. Notice that the DCE transmits on RX and receives on TX.
Rule
The speeds at which the two devices are communicating on the RS-232 must
be the same. If they are not, you'll get a speed mismatch, where either
garbage or nothing appears on the screen when dialing in to the modem.
Configuration Reference Notes
- access server: speed xxxxx
- modem: configuration commands vary from modem to modem. Check your
modem manual under options such as port-rate adjust, buffered
mode, or
lock dte. Often, just turning on error correction for the modem
will
make it go into buffered mode, which may lock the speed.
In order to lock the modem at the new access server speed, you may need
to set the speed on the access server first, then send an AT command to
the modem with a reverse telnet. You'll find more details about this in
the section "Connecting the Modem" below.
RTS/CTS - Hardware Flow Control
Request to Send: DTE >---RTS---> DCE
Clear to Send: DTE <---CTS---< DCE
This pair of wires indicates the ability of a device to receive data.
For example, when the DCE has a full data buffer and can no longer
accept data from the DTE for transmitting, it will lower the CTS signal.
When the access server can no longer accept data, it lowers the RTS
signal.
Rule
Both the access server and the modem must agree to hardware handshake
with CTS/RTS.
Configuration Reference Notes
- access server: flowcontrol hardware
- modem: configuration commands vary from modem to modem. Look for
"Hardware Handshaking" or "RTS/CTS Flow Control" in the modem manual.
Both the access server and the modem must be set for Hardware Flow
Control. If they do not agree on handshaking, they will tend to overflow
each other's buffers. Dropped characters or packet errors are typical
signs of a handshaking mismatch.
DTR/DCD - Modem Control
Data Terminal Ready: DTE >---DTR---> DCE
Data Carrier Detect: DTE <---DCD---< DCE
This pair of wires is used between the DTE and the DCE to initiate and
receive calls. When the access server is ready, DTR output is high. The
access server lowers DTR to drop any existing calls and return to the
stored configuration. The modem uses DCD output to indicate that a call
has arrived that needs servicing by the access server. The modem drops
DCD to indicate loss of the call.
Rule
The access server and modem must agree on the function of DTR and DCD.
Configuration Reference Notes
- access server: modem inout or modem ri-is-cd
Use modem inout to allow incoming and outgoing connections to the
modem.
You will need modem inout while configuring the modem. Use
modem ri-is-
cd to allow incoming only connections. Cabling other than what we
suggested at the beginning of this section can cause modem control to
fail since modem DCD may not be wired.
- modem: usually &c1 and &d2
This is often referred to as RS-232 standard operation.
Configuring the Cisco Side
Now let's start configuring. On the Cisco, this line configuration
usually works best:
line x
! where x = TTY #. AUX port is 1 on router, last_tty+1 on access server.
speed 38400
! Set to highest speed in common between modem and port.
flow hard
! RTS/CTS flowcontrol. CTS only on ASM.
modem inout
! Drop connection on loss of CD, Cycle DTR for connection close
Each line in this configuration assumes that the modem will be set up in
a specific way, which you'll see how to accomplish using the chart at
the end of this document. Specifically, it assumes that we will lock DTE
speed, set hardware (RTS/CTS) flowcontrol, set carrier detect to reflect
the actual carrier state, and set the modem to hang up on loss of DTR.
Flowcontrol and modem control are not available on pre-9.21 router aux
ports.
- If flowcontrol is not available, stay at 9600 baud.
- Don't use the Cisco autobaud feature. Today's modems do a much better
job.
- If you are routing over the AUX port, remember that each character
generates a processor interrupt. Abnormally high CPU may be resolved by
using a lower AUX port speed.
Bit rate trivia:
- 38400 is the maximum speed for the 500-CS and AUX ports.
- 57600 is the maximum speed for ASM, STS-10.
- 115200 is the maximum speed for the 25xx access servers.
Connecting the Modem
Attach the modem to a port, and configure your modem using reverse
connection. To do this, issue the command
telnet x.x.x.x 20yy
where x.x.x.x is any active, connected, and up interface on the Cisco
device and yy is the line number to which you want to connect.* You can
issue this telnet command from anywhere on the network that can ping
x.x.x.x.
Recall that 01 is the AUX port on a router. On an Access
server, the
AUX port is the last_tty+1 - that is, on a 16-port Access Server, the
AUX port is port 17.
If you get a connection refused, either someone already has a connection
to that port or there is an exec (prompt) running on that port. Clear
the line from the console to try again by issuing the command
clear line yy
where yy is the line number. If it still fails, make sure that you have
set modem inout for that line. If you don't have modem control (as in
pre-9.21 AUX ports), set no exec on the line before making a reverse
connection. If you still get a connection refused, disconnect the modem,
issue the command
telnet x.x.x.x 20yy
and then reconnect and configure the modem. As a last resort, configure
the modem using an external terminal. Be sure to clear the line before
each connection attempt.
Configuring the Modem
Once you've attached to the modem at the same speed to which the Cisco
port will be set (through a reverse telnet connection), you're ready to
issue the AT commands. You can build the exact command string you need
from the attached chart. Just follow these steps:
- As a minimum, you must start with the information in the REQUIRED FOR
ALL column and the EC/COMPRESSION pair that you need (either BEST or
NO). Use the BEST pair for applications that are primarily file
transfer. Use the NO pair for connections that are primarily ARA,
Xremote, or interactive packet-protocol (SLIP/PPP) traffic. Generally,
Cisco recommends BEST. Adjust your configuration as your needs change.
- If you have an AUX port (or no modem control), add the AUX PORT
section. Remember to limit to 9600 bps if you have no flow control.
- Add the PLAT SPEC ASM only for ASM platforms, and CAB-MDCE if you
have a 500-CS with a CAB-MDCE.
- Finalize the string with an &W.
For example, a Microcom modem with best error correction/compression
with an ASM would need this string:
AT&FS0=1&C1&D3\Q3\J0\N6%C1\Q2&W
Some Hard-Learned Hints and Tricks
- If you dial up and connect, and you get no response, try ^U (clear
line) and ^Q (XON) and a few returns to wake it up.
- If you type "quit" and the modem doesn't hang up, the modem is not
watching DTR or you have not set modem inout on the Cisco.
- If you land in someone else's session when you dial in, the modem is
not dropping CD on disconnect or you have not set up modem inout on the
Cisco.
Remember, you cannot set up modem control on pre-9.21 router aux
ports.
- If you issue a +++ on the dialing modem, followed by an
ATO to
reconnect and you find that you are frozen, this means the answering
modem saw and interpreted the +++ when it was echoed to you. This
is a
bug - a fairly common one - in the answering modem. Set ATS2=255 or
ATS2=128 on the answering modem.
- If you have autoselect turned on for the line (9.21 and after), a
carriage return is required to see a prompt.
- If you do hardware flow control (which is recommended), make sure the
Router/Access Server's line (DTE) and the modem (DCE) both have that
feature enabled. Having one on and the other one off will cause you to
lose data.
- If you have an MDCE, your life will be a lot simpler if you turn it
into an MMOD by moving pin 6 to pin 8 (most modems use CD and not DSR to
indicate the presence of a carrier). Otherwise, some modems can be
programmed to sprocide carrier information via DSR (see chart below). If
you do not know what an MDCE is, disregard this paragraph.
Deciphering the Chart
*NA* means that option is not available on that modem.
--> means the command on the right will take care of that function.
<-- means the command on the left will take care of that function.
AUX PORT parameters are only required for pre-9.21 aux ports or any
other port without modem control set.
PLAT SPEC parameters are the platform specific parameters required for
ASM (no RTS) or 500-CS CAB-MCDCE (requires DSR to performs the CD
function).
COMMENTS alert you to modem-specific weirdness.
=========REQUIRED FOR ALL========= =======EC/COMPRESSION=======
MODEM BRAND FD AA CD DTR RTS/CTS LOCK DTE Best Best No No
Hngp Flow Speed Error Comp Error Comp
=============================================================================
Codex 3260 &F S0=1 &C1 &D3 *FL3 *SC1 *SM3 *DC1 *SM1 *DC0
USR Courier &F S0=1 &C1 &D3 &H1&R2 &B1 &M4 &K1 &M0 &K0
USR Sportster
Global Village &F S0=1 &C1 &D3 \Q3 \J0 \N7 %C1 \N0 %C0
Teleport Gold
AT&T Paradyne &F S0=1 &C1 &D3 \Q3 ---> \N7 %C1 \N0 %C0
Dataport
Hayes modems &F S0=1 &C1 &D3 &K3 &Q6 &Q5 &Q9 &Q6 <---
Accura/Optima
Microcom &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
QX4232 series
Motorola UDS &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
FastTalk II
Multitech &F S0=1 &C1 &D3 &E4 $BA0 &E1 &E15 &E0 &E14
MT1432 MT932
Viva &F S0=1 &C1 &D3 &K3 ---> \N3 %M3 \N0 %M0
14.4/9642c
ZyXel &F S0=1 &C1 &D3 &H3 &B1 &K4 <--- &K0 <---
U-1496E
Supra &F S0=1 &C1 &D3 &K3 ---> \N3 %C1 \N0 %C0
V.32bis/28.8
ZOOM &F S0=1 &C1 &D3 &K3 ---> \N3 %C2 \N0 %C0
14.4
Practical &F S0=1 &C1 &D3 &K3 ---> &Q5 &Q9 &Q6 <---
Peripherals
Megahertz &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
=AUX PORT= =PLAT SPEC=
MODEM BRAND No No ASM CAB- Write COMMENTS
Echo Res only MDCE Memory
=============================================================================
Codex 3260 E0 Q1 *NA* &S1 &W
USR Courier E0 Q1 &R1 *NA* &W Cool stuff on ftp.usr.com
USR Sportster
Global Village E0 Q1 \Q2 *NA* &W
Teleport Gold
AT&T Paradyne E0 Q1 \Q2 *NA* &W
Dataport
Hayes modems E0 Q1 *NA* *NA* &W
Accura/Optima
Microcom E0 Q1 \Q2 *NA* &W Almost all Microcom modems
QX4232 series have similar config params.
Motorola UDS E0 Q1 \Q2 *NA* &W
FastTalk II
Multitech E0 Q1 &E12 &S1 &W Lock speed with AT$SB38400
All models (or your favorite speed)
Viva E0 Q1 *NA* &S1 &W
14.4/9642c
ZyXel E0 Q1 *NA* &S1 &W Cool stuff on ftp.zyxel.com
U-1496E
Supra E0 Q1 *NA* &S1 &W
V.32bis/28.8
ZOOM E0 Q1 *NA* &S1 &W
14.4
Practical E0 Q1 *NA* *NA* &W Based on PC288LCD. May vary.
Peripherals
Megahertz E0 Q1 \Q2 *NA* &W
Posted: Jun 19 15:42:06 1995
|
Title: Cisco - Modem Configuration For Those Who Hate Modems
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Modem Configuration For Those Who Hate Modems
Introduction
This document will show you how to configure most popular modems to work on
the Cisco access server or on the console/aux port of our routers. Also,
we'll give you some insider hints and tricks that we've found helpful in
taming troublesome modems.
Configuring the Cisco Side
This line configuration usually works best:
line x
! where x = TTY #. Aux port is 1 on router, last_tty+1 on access server.
speed 38400
! Set to highest speed in common between modem and port.
flow hard
! RTS/CTS flowcontrol. CTS only on ASM.
modem inout
! Drop connection on loss of CD, Cycle DTR for connection close
transport input all
! Use all supported protocols (including MOP and Telnet)
Each line in this configuration assumes that the modem will be set up in a
specific way, which you'll see how to accomplish using the chart at the end
of this document. Specifically, it assumes that we will lock DTE speed, set
hardware (RTS/CTS) flowcontrol, set carrier detect to reflect the actual
carrier state, and set the modem to hang up on loss of DTR. Flowcontrol and
modem control are not available on pre-9.21 router aux ports.
- If flowcontrol is not available, stay at 9600 baud.
- Don't use the Cisco autobaud feature. Today's modems do a much better
job.
- If you are routing over the aux port, remember that each character
generates a processor interrupt. Abnormally high CPU may be resolved by
using a lower AUX port speed.
Bit rate trivia:
- 38400 is the maximum speed for the 500-CS
- 57600 is the maximum speed for ASM, STS-10 and AUX ports
- 115200 is the maximum speed for the 25xx access servers
Connecting the Modem
Attach the modem to a port, and configure your modem using reverse
connection. To do this, issue the command
telnet x.x.x.x 20yy
where x.x.x.x is any active, connected, and up interface on the Cisco
device and yy is the line number to which you want to connect.* You can
issue this telnet command from anywhere on the network that can ping
x.x.x.x.
Recall that 01 is the aux port on a router. On an Access server, the AUX
port is the last_tty+1 - that is, on a 16-port Access Server, the AUX
port is port 17.
If you get a connection refused, either someone already has a connection to
that port or there is an exec (prompt) running on that port. Clear the line
from the console to try again by issuing the command
clear line yy
where yy is the line number. If it still fails, make sure that you have set
modem inout for that line. If you don't have modem control (as in pre-9.21
aux ports), set no exec on the line before making a reverse connection. If
you still get a connection refused, disconnect the modem, issue the command
telnet x.x.x.x 20yy
and then reconnect and configure the modem. As a last resort, configure the
modem using an external terminal. Be sure to clear the line before each
connection attempt.
Configuring the Modem
Once you've attached to the modem at the same speed to which the Cisco port
will be set (through a reverse telnet connection), you're ready to issue
the AT commands. You can build the exact command string you need from the
attached chart. Just follow these steps:
- As a minimum, you must start with the information in the REQUIRED FOR ALL
column and the EC/COMPRESSION pair that you need (either BEST or NO). Use
the BEST pair for applications that are primarily file transfer. Use the
NO pair for connections that are primarily ARA, Xremote, or interactive
packet-protocol (SLIP/PPP) traffic. Generally, Cisco recommends BEST.
Adjust your configuration as your needs change.
- If you have an AUX port (or no modem control), add the AUX PORT section.
Remember to limit to 9600 bps if you have no flow control.
- Add the PLAT SPEC ASM only for ASM platforms, and CAB-MDCE if you have a
500-CS with a CAB-MDCE.
- Finalize the string with an &W.
For example, a Microcom modem with best error correction/compression with
an ASM would need this string:
AT&FS0=1&C1&D3\Q3\J0\N6%C1\Q2&W
Some Hard-Learned Hints and Tricks
- If you dial up and connect, and you get no response, try ^U (clear
line)
and ^Q (XON) and a few returns to wake it up.
- If you type quit and the modem doesn't hang up, the modem is not
watching
DTR or you have not set up modem inout on the Cisco.
- If you land in someone else's session when you dial in, the modem is not
dropping CD on disconnect or you have not set up modem inout on the
Cisco. Remember, you cannot set up modem control on pre-9.21 router aux
ports.
- If you issue a +++ on the dialing modem, followed by an ATO
to reconnect
and you find that you are frozen, this means the answering modem saw and
interpreted the +++ when it was echoed to you. This is a bug - a
fairly
common one - in the answering modem. Set ATS2=255 or ATS2=128 on the
answering modem.
- If you have autoselect turned on for the line (9.21 and after), a
carriage return is
required to see a prompt.
- If you elect to do hardware flow control (which is recommended), make
sure the Router/Access Server's line (DTE) and the modem (DCE) both have
that feature enabled. Having one on and the other one off will cause you
to lose data.
- If you have an MDCE, your life will be a lot simpler if you turn it into
an MMOD by moving pin 6 to pin 8 (most modems use CD and not DSR to
indicate the presence of a carrier). Otherwise, some modems can be
programmed to sprocide carrier info via DSR (see chart below). If you do
not know what an MDCE is, disregard this paragraph.
Deciphering the Chart
*NA* means that option is not available on that modem.
--> means the command on the right will take care of that function.
<-- means the command on the left will take care of that function.
AUX PORT parameters are only required for pre-9.21 aux ports or any other
port without modem control set.
PLAT SPEC parameters are the platform specific parameters required for ASM
(no RTS) or 500-CS CAB-MCDCE (requires DSR to performs the CD function).
COMMENTS alert you to modem-specific weirdness.
-----------------------------------------------------------------------------
--------REQUIRED FOR ALL---------- ------EC/COMPRESSION-----
MODEM BRAND FD AA CD DTR RTS/CTS LOCK DTE Best Best No No
Hngp Flow Speed Error Comp Error Comp
-----------------------------------------------------------------------------
Codex 3260 &F S0=1 &C1 &D3 *FL3 *SC1 *SM3 *DC1 *SM1 *DC0
USR Courier &F S0=1 &C1 &D3 &H1&R2 &B1 &M4 &K1 &M0 &K0
USR Sportster
Global Village &F S0=1 &C1 &D3 \Q3 \J0 \N7 %C1 \N0
%C0
Teleport Gold
AT&T Paradyne &F S0=1 &C1 &D3 \Q3 ---> \N7 %C1 \N0 %C0
Dataport
Hayes modems &F S0=1 &C1 &D3 &K3 &Q6 &Q5 &Q9 &Q6 <---
Accura/Optima
Microcom &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
QX4232 series
Motorola UDS &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
FastTalk II
Multitech &F S0=1 &C1 &D3 &E4 $BA0 &E1 &E15 &E0 &E14
MT1432 MT932
Viva &F S0=1 &C1 &D3 &K3 ---> \N3 %M3 \N0 %M0
14.4/9642c
ZyXel &F S0=1 &C1 &D3 &H3 &B1 &K4 <--- &K0 <---
U-1496E
Supra &F S0=1 &C1 &D3 &K3 ---> \N3 %C1 \N0 %C0
V.32bis/28.8
ZOOM &F S0=1 &C1 &D3 &K3 ---> \N3 %C2 \N0 %C0
14.4
Practical &F S0=1 &C1 &D3 &K3 ---> &Q5 &Q9 &Q6 <---
Peripherals
Megahertz &F S0=1 &C1 &D3 \Q3 \J0 \N6 %C1 \N0 %C0
-----------------------------------------------------------------------------
-AUX PORT- -PLAT SPEC-
MODEM BRAND No No ASM CAB- Write COMMENTS
Echo Res only MDCE Memory
-----------------------------------------------------------------------------
Codex 3260 E0 Q1 *NA* &S1 &W
USR Courier E0 Q1 &R1 *NA* &W Cool stuff on ftp.usr.com
USR Sportster
Global Village E0 Q1 \Q2 *NA* &W
Teleport Gold
AT&T Paradyne E0 Q1 \Q2 *NA* &W
Dataport
Hayes modems E0 Q1 *NA* *NA* &W
Accura/Optima
Microcom E0 Q1 \Q2 *NA* &W Almost all Microcom modems
QX4232 series have similar config params.
Motorola UDS E0 Q1 \Q2 *NA* &W
FastTalk II
Multitech E0 Q1 &E12 &S1 &W Lock speed with AT$SB38400
All models (or your favorite speed)
Viva E0 Q1 *NA* &S1 &W
14.4/9642c
ZyXel E0 Q1 *NA* &S1 &W Cool stuff on ftp.zyxel.com
U-1496E
Supra E0 Q1 *NA* &S1 &W
V.32bis/28.8
ZOOM E0 Q1 *NA* &S1 &W
14.4
Practical E0 Q1 *NA* *NA* &W Based on PC288LCD. May vary.
Peripherals
Megahertz E0 Q1 \Q2 *NA* &W
Posted: Tue Jun 24 11:00:29 PDT 1997
|
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|
