3Com Router User Manual

							Troubleshooting DCC747
Use the DCC Debugging 
Information to Locate 
ProblemsEnabling DCC debugging
Execute the following commands in system view for displaying the DCC 
debugging information:
[Router] debugging dialer event
[Router] debugging dialer packet
[Router] info-center enable
Output debugging information for the interconnection failure between 
DCC and the remote end and diagnosis 
In this section, the debugging information that may be output when DCC cannot 
reach the remote end will be displayed and explained. The user can solve the 
problems with the solutions recommended in this section.
Ta b l e 774   DCC Fault Messages
MessageFault
DCC: Receive CALL_DISC_INDThe debugging information is probably output 
because:
The physical connection between the local and 
remote ends is down, phone cable is not securely 
connected to the router, or the quality of phone 
line is not good.
PPP authentication is not correctly configured, so 
the PPP authentication is failed.
Remote DCC authentication is failed, because 
name in the commands dialer user and dialer 
route configured for DCC is inconsistent with 
name configured for PPP authentication, and the 
dialer route at the remote end does not contain 
the local network address.
The remote end disconnects the connection 
because the remote DCC idle-timeout timer has 
timed out.
Solution:
If PPP configuration is incorrect or name 
configurations are inconsistent, implement the 
configuration as shown in the above example.
If it is the problem of the network address, apply 
the following measures in the configuration of the 
remote end: Add the dialer route corresponding to 
the network address of the local router on the 
remote router. Alternatively, remove all the dialer 
routes configured at the remote end, and use the 
dial number.
DCC: link negotiation Down on 
interface ***The link is probably disconnected because PPP 
negotiation is failed due to a wrong PPP 
configuration. To solve the problem, refer to the 
previous example to make the configuration.
DCC: NAME authentication ERROR, 
failedThe debugging information is probably outputted 
because name configured in the commands dialer 
user and dialer route is inconsistent with that 
configured in PPP authentication. The connection is 
disconnected since the local DCC authentication 
has been failed. To solve the problem, refer to the 
previous example to make the configuration. 
						

							748CHAPTER 51: CONFIGURING DCC
DCC: peeraddr matching  error 
on interface ***, shutdown linkThe debugging information is probably outputted 
because the local dialer route does not contain the 
remote network address. To solve the problem, add 
the dialer route corresponding to the remote 
network address on the local router or use the dial 
number after removing all the dialer routes 
configured on the local router.
DCC: idle-timeout on interface 
*** , shutdown! start 
enable-timeThe debugging information does not indicate any 
error. DCC normally disconnects the connection, 
because the local DCC idle-timeout timer has been 
timed out.
DCC: wait-for-carrier-timeout 
on a link on interface ***, 
shutdown!start enable-timeThe debugging information is probably outputted 
because the local router cannot contact the remote 
end for a long time. It may occur because the 
remote end is busy or the quality of the phone line 
is bad.
DCC: The interface has no 
dialer-group, discard the 
packet!The debugging information is probably outputted 
because the dialer-group command has not been 
configured on the corresponding dialer interface or 
the physical interface on which DCC is directly 
enabled. To solve the problem, refer to the previous 
example to make the configuration.
DCC: there is not a dialer 
number on the interface, 
failed, discard packetThe debugging information is probably outputted, 
because neither dialer route nor the dialer 
number is configured on the corresponding dialer 
interface or the physical interface on which DCC is 
enabled directly. To solve the problem, configure 
the dialer route and the dialer number on the local 
end for the outbound call at the local end.
DCC: Enable-timeout is 
effective , failedRather than indicating an error, the outputted 
debugging information means that the 
enable-timeout timer on the corresponding physical 
interface have not timed out yet. The physical 
interface can be used for dialing upon the timeout 
of the timer.
Message Fault 
						

							52
CONFIGURING MODEM 
This chapter covers the following topics:
■Modem Function Provided by 3Com Routers
■Configuring a Modem
■Displaying and Debugging a Modem
■Modem Configuration Examples
■Troubleshooting
Modem Function 
Provided by 3Com 
RoutersTo offer the optimal flexibility, 3Com routers provide the following modem 
management functions:
■Provide the scripts (modem script) for modem management to enable the user 
to better control the modems connected to the router. A modem script can be 
executed by the following two means:
■Executes a modem script directly through the script-string command to 
initialize the modem or other configurations.
■Triggers the modem script with particular events, such as router startup, 
modem dial-in connection, and the 
start-chat command.
■Using the script along with the related commands can enhance the remote 
configuration function of router. If the asynchronous serial interface works in 
flow mode, the user can establish a remote connection to the interface 
through the dumb terminal or modem dialup, to configure and manage the 
router.
■Directly send AT commands to the modem via the serial interface for managing 
the modem.
■Interwork with the equipment of other equipment vendors. That is, the 
asynchronous serial interfaces of the participating parties are working in the 
flow mode and interconnected through modems.
■Provides rich debugging information for modem monitoring and maintenance.
Modem Script3Com routers provide t modem scripts, which are mainly used for:
■Flexibly controlling the modems of different models. For example, using 
different initialization AT commands able to interoperate with 3Com routers.
■Implementing the interactive login to remote systems. Interactive negotiation 
of the scripts can enable the system enters different link states. For example, 
after the asynchronous serial interfaces on the two routers set up a connection 
through the modem, routers can negotiate the protocol to be encapsulated 
with the physical link and its operating parameters. 
						

							750CHAPTER 52: CONFIGURING MODEM
Syntax description of modem script 
The modem script format in common use is as follow:
receive-string1 send-string1 receive-string2 send-string2......
Where:
■Normally, receive-string and send-string appear in pairs, and the script must 
begin with a receive-string. For example, “receive-string1 send-string1” 
represents the execution flow: Expect to receive receive-string1, and send 
send-string1 to the modem if the received string matches receive-string1 
before timing out. Otherwise, the execution of the subsequent script will be 
terminated.
■If the last string is a send-string, it indicates that the execution of the script will 
be terminated after the string is sent without waiting for any receive-string.
■If it is unnecessary to receive a string at the beginning of a script, and the 
system can directly wait for the send-string, then the user can set the first 
receive string to , which will be explained later.
■Except for ending with “\c”, the send-string will be automatically added with 
an additional return character to its end when it is sent.
■A receive-string is matched via the location-independent matching method. 
That is, the match is considered successful as long as the received contents 
contain the expected string.
■The match operation on a receive-string will be considered successful if the 
receive-string is matched with any expected receive-strings which are separated 
with “-“. 
■The default timeout time waiting for a receive-string is 5 seconds. TIMEOUT 
seconds can be inserted into the script anytime to adjust the timeout time 
waiting for the receive-string, which is valid till a new TIMEOUT is set in the 
same script.
■All the strings and keywords in a script are case sensitive.
■Both the strings and keywords are separated by spaces. If a space is contained 
in a string, it should be put in the double quotation marks ( ). A pair of 
empty quotation marks (that is, ) have two meanings. Being a leading  in 
a script, it means that no string is expected from the modem and the system 
will directly send the strings to the modem. If  locates in any other locations, 
the string content will be regarded to be .
■ABORT receive-string can be inserted at any point in a script to change the 
script execution flow. Its presence in the script indicates that the script 
execution will be terminated if a received string is fully matched the 
receive-string set by ABORT receive-string. Multiple ABORT entries can be 
defined in a script, and they will take effect concurrently. Once a received string 
matches any of them, the script execution will be terminated. Regardless of 
where the ABORT receive-string is placed, it will take effect in the whole script 
execution process.
■Escape characters can be inserted in a script for the purpose of better 
controlling the script and increasing its flexibility. In addition, all the escape 
characters are the delimiters in the string at the same time. 
						

							Configuring a Modem751
Ta b l e 775   Script Keywords
In which, seconds defaults to 180 and is in the range of 0 to 180.
Ta b l e 776   Script Escape Characters
Configuring a ModemModem Configuration includes:
■Configure the Modem Dial-in and Dial-out Authorities
■Configure Modem Through the AT Command
■Configure a Modem Script
■Execute a Modem Script Manually
■Specify the Events that Trigger Modem Scripts
■Configure the modem-related operation mode for the asynchronous interface
■Configure the Modem Answer Mode
■Configure Authentication for a Modem Dial-in User
Configure the Modem 
Dial-in and Dial-out 
AuthoritiesPerform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
Ta b l e 777   Configure the Modem Dial-In and Dial-Out Authorities 
By default, modem dial-in and dial-out are allowed.
KeywordDescription
ABORT receive-stringThe string following ABORT will be compared with the strings sent 
from a modems or remote DTE device for a match. The match mode 
is full match. Multiple ABORT entries can be configured for a script, 
and all of them take effect in the whole script execution period.
TIMEOUT secondsThe digit following TIMEOUT is used to set the timeout interval that 
the device waits for receiving strings. If no expected strings are 
received within the interval, the execution of the script will fail. 
Once being set, the setting will be valid till a new TIMEOUT is set.
Escape characterDescription
\cOnly the specified string can be sent and the character Enter will 
not be sent.The character of \c must be at the end of the sending 
strings. Otherwise,it is invalid at other location.
\dRepresents pausing 2 seconds.
\nRepresents the character newline.
\rRepresents the character Enter.
\sRepresents the character Space.
\tRepresents the character Tab.
\\Represents the character \.
\TRepresents telephone number.
OperationCommand
Enable only modem dial-inmodem in
Enable only modem dial-outmodem out
Enable both modem dial-in and dial-outmodem
Disable both modem dial-in and dial-outundo modem 
						

							752CHAPTER 52: CONFIGURING MODEM
Configure Modem 
Through the AT 
CommandPerform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
Ta b l e 778   Configure a Modem Script
A modem can accept the AT commands only when it is in AT command mode. If it 
is forwarding data, the AT command sent via the 
sendat at-string command is 
invalid.
Configure a Modem 
ScriptPerform the following configuration in system view.
Ta b l e 779   Configure a Modem Script
For the format of script, refer to the modem script syntax description.
Execute a Modem Script 
ManuallyIf necessary, the user can execute the modem script through the start-chat 
command for managing the external modem to which the interface is connected.
Perform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
Ta b l e 780   Execute a Modem Script Manually
Specify the Events that 
Trigger Modem ScriptsAssociating modem scripts with events, is to automatically execute the 
corresponding script after a particular event occurs to the router. In 3Com routers, 
the following script events are supported:
■An outgoing call is established to a line: The specified script will be executed if 
a modem outgoing call is established.
■An incoming call is established to a line: The specified script will be executed if 
a modem incoming call is established.
■DCC dial: Start the dial script when implementing DCC dial.
■Line reset: Execute the specified script when a line is disconnected.
■Power on the system and reboot it: Execute the specified script on the 
corresponding asynchronous serial interface when the system is powered on 
and initialized.
For the the events in the previous list, the corresponding scripts can be specified 
through the script command.
OperationCommand
Configure modem through the AT 
Commandsendat at-string
OperationCommand
Define a modem scriptscript-string script-name 
script-content
Delete the modem scriptundo script-string script-name
OperationCommand
Manually execute a modem scriptstart-chat script-name 
						

							Configuring a Modem753
Perform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
Ta b l e 781   Specify the Events Triggering the Modem Scripts
The argument following the script init-string command is the initialization 
string rather than the modem script name. 
Configure the Modem 
Answer Mod
e
This configuration depends on whether the external modem to which the 
asynchronous interface is connected is in auto-answer mode (whether the AA LED 
on the modem is on). If the modem is in auto-answer mode, the user should 
execute 
modem-autoanswer before using the dial function. If not, the user should 
execute 
undo modem-autoanswer. Inconsistency of the configuration and the 
modem status may cause the abnormal acceptance of some modem incoming 
calls.
Perform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
Ta b l e 782   Configure the Answer Mode for the Modem
By default, the modem works in non-auto answer mode.
Configure 
Authentication for a 
Modem Dial-in UserThe command modem-login is configured to authenticate the name and password 
of the dial-in user. Generally this command is used together with the command of 
script trigger connect, thus many usernames can login at the same interface. 
Perform the following configuration in interface (asynchronous serial, AUX or AM 
interface) view.
OperationCommand
Specify the automatically executed modem 
script when the calling-out connection is set 
up successfully.script trigger login script-name
Specify the automatically executed modem 
script when the calling-in connection is set up 
successfully.script trigger connect script-name
Specify the automatically executed modem 
script before DCC dialing.script trigger dial script-name
Specify the automatically executed modem 
script at the time of line reset.script trigger logout script-name
Specify the automatically executed modem 
script at the time of system power-on and 
restart.script trigger init script-name
Specify the default modem initialization string 
for initializing modem.script init-string init-string
OperationCommand
Configure the modem to work in 
auto-answer modemodem auto-answer
Configure the modem to work in 
non-auto answer modeundo modem auto-answer 
						

							754CHAPTER 52: CONFIGURING MODEM
Ta b l e 783   Configure Authentication for Modem Dial-In User
By default, the authentication for a modem dial-in user is not configured.
Displaying and 
Debugging a ModemExecutethe debugging command in all views for the debugging.
Ta b l e 784   Display and Debug Modem
Modem Configuration 
ExamplesThis section provides the following examples:
■Managing a Modem Through a Modem Script
■Power-on Initialization through the Initialization Script
■Use the Script to Dial Directly
■Authentication for Modem Dial-in User
Managing a Modem 
Through a Modem ScriptConfigure a Modem adaptation baud rate
On the asynchronous interface connected to the modem, use a standard AT 
command to configure the modem baud rate, and send the “AT” command to 
the modem. If “OK” is received from the modem, it indicates that the modem can 
automatically adapt to the corresponding baud rate. Then, write the configuration 
into the modem for conservation, and the corresponding AT command is 
“AT&W”.
Figure 241   Network of the configuration for the router to manage the modem
1Configure a modem script.
[Router]script-string baud  AT OK AT&W OK
2Execute the corresponding script in interface view, supposing the modem is 
connected to the interface Serial0.
[Router]interface serial 0
[Router-Serial0]start-chat baud
OperationCommand
Configure authentication for modem 
dial-in usermodem-login
Delete authentication for modem dial-in 
userundo modem-login
OperationCommand
Enable debugging of the AT command of 
modemdebugging modem at [ interface type 
number ]
Enable modem event debuggingdebugging modem event [ interface 
type number ]
PC
PSTN
Router
Modem 
						

							Modem Configuration Examples755
Restore the ex-factory modem settings
To restore the ex-factory modem settings, use the “AT&F” command.
[Router]script-string factory  AT OK AT&F OK
[Router]interface serial 0
[Router-Serial0]start-chat factory
Configure the modem initialization parameters
Correctly initializing the modem configuration is an important step for the correct 
connection with the modem. The following contents briefly introduce the 
conventional AT initialization commands and the works for initialization.
■When the negotiation is being carried out between modems, the modem 
speed must not be changed. Otherwise, the user should send an AT command 
to the remote modem so that the modem can be set to the new speed.
■The port speed must not change when a session is negotiated with a remote 
modem. If the speed of the port on the access server is changed, you must 
establish a direct Telnet session to the modem and send an AT command so 
that the modem can be set to the new speed.
■Modems differ in the method they use to lock the EIA/TIA-232 serial interface 
speed. Refer to the modem documentation to learn how the modem locks the 
modem speed (check the settings &b, \j, &q, 
, or s-register settings).
■The modem must use the data carrier detect (DCD) to indicate when a 
connection is established with a remote end. Most modems use the &c1 
command to implement the configuration. Refer to the modem 
documentation for details.
■The modem must disconnect the modem active connections via the data 
terminal ready (DTR) signals. Most modems use &d2 or &d3 to implement the 
setting. Refer to the modem documentation for details.
■If the modem is required to access incoming calls, it must be configured with 
the number of off-hook ringing for incoming calls. The user should not to 
adopt the ringing auto-answer mode. S0=0 is adopted to make the 
configuration for most of the modems. For details, please refer to the modem 
operation manuals provided by the related manufacturers.
Considering the previously listed situations, the following initialization string is 
designed for typical applications:
AT&b1&c1&d2&s0=0
The initialization string enables the following functions:
■Locks the speed of the modem to the serial interface speed
■Enables DCD 
■Enables disconnection of DTR
■Configures the non-auto answer
[Router]script-string init  AT&b1&c1&d2&s0=0 OK
[Router]interface serial 0
[Router-Serial0]start-chat init 
						

							756CHAPTER 52: CONFIGURING MODEM
Power-on Initialization 
through the 
Initialization ScriptEnable the router to initialize the modem to which the asynchronous interface is 
connected when powering on the router or rebooting it.
[Router] script-string init  AT OK AT&B1&C1&D2&S0=1 OK AT&W OK
[Router] interface async 0
[Router-Async0] modem
[Router-Async0] start-chat init
Use the Script to Dial 
DirectlyConfigure a modem script and direct dial.
[Router] script-string dial  AT OK ATDT8810058 CONNECT
[Router] interface async 0
[Router-Async0] modem
[Router-Async0] start-chat dial
Authentication for 
Modem Dial-in UserBefore logging in network through dialing, multiple users who connect with 
modem are authenticated on 3Com router based on username and password. 
Only the authenticated users can logging in network, and those who have failed 
the authentication are not allowed to log in. 
Figure 242   Network of authentication for modem dial-in user
1Configure a modem script.
[Router] script-string welcome  Welcome use 3Com router!
2Configure a modem user, and enable AAA authentication.
[Router] local-user testuser password simple testuser service 
exec-operator
[Router] aaa-enable
[Router] aaa authentication-scheme login default local
[Router] aaa accounting-scheme optional
3Execute specified script in serial0 interface view.
[Router] interface serial 0
[Router-Serial0] modem-login
[Router-Serial0] script trigger connect welcome
[Router-Serial0] undo modem auto-answer
TroubleshootingThe modem is in abnormal status (such as the dial tone or busy tone 
remains for a long time).
Do the following:
■Execute the commands shutdown and undo shutdown on the router physical 
interface connected to the modem to check whether the modem has been 
restored to normal status.
PC
PSTN
RouterMod em