3Com Router User Manual

							4
TERMINAL SERVICE
This chapter includes information on the following topics:
■Terminal Service Overview
■Terminal Message Service
■Dumb Terminal Service
■Terminal Service of Telnet Connection
■Rlogin Terminal Service
■X.25 PAD Remote Access Service
Terminal Service 
OverviewThe terminal services provided by the 3Com Router to access the command line 
interface are as follows:
■Perform terminal configuration via Console port
■Perform terminal configuration via asynchronous serial port
■Perform terminal configuration via Telnet connection
■Perform terminal configuration via RLogin connection
■Perform remote login via X.25 PAD
■Perform terminal message service
Features of Terminal 
Service at Console PortThe Local configuration environment can be established via the console port. 
Please refer to 
Chapter 2 “3Com Router User Interface”for specific method.
The features of the terminal service at the console port are shown in the following 
table. Parameters of the terminal program running on the computer should be set 
according to this table.
Ta b l e 37   Features of terminal service at console port
Service typeFeatures
Echo modeNo local echo
Terminal emulation typeVT100
Baud rate9600 bps
Data bit8 bits
Parity checkNone
Stop bit1 bit
Flow controlNone 
Binary transmission protocolXmodem  
						

							58CHAPTER 4: TERMINAL SERVICE
Features of Terminal 
Service at Async Serial 
PortThe 3Com Router supports remote configuration on the router via asynchronous 
serial port (including synchronous/asynchronous serial port, 8/16 asynchronous 
serial port, and AUX port). Please refer to 
Chapter 2 “3Com Router User 
Interface”of this manual for the specific method to establish the configuration 
environment.
The remote terminal service features of the asynchronous serial port are shown in 
the following table. Parameters of the terminal program running on the computer 
should be set according to this table, and parameters such as baud rate, data bit, 
parity check and flow control should be consistent with those of corresponding 
router interfaces.
Ta b l e 38   Remote terminal service features of the asynchronous serial port
Set the Attributes of 
Terminal Service Usually, the terminal user connected via the console port can last for 3 minutes. 
The time for the dumb terminal user can last for 10 minutes. For the user who 
uses the dummy terminal in dial-up mode, the disconnection timeout is 6 minutes 
but the user can disable this function by using the 
undo idle-timeout command 
so that all the terminal users will never be disconnected. 
Perform the following configuration in system view.
Ta b l e 39   Set the attributes of terminal service
By default, the system will enable the timeout disconnection of the terminal user.
Terminal Message 
ServiceWhenever the terminal users that log into the same router want to communicate 
with each other, they can use the terminal message service to send messages. The 
remote users can telnet onto the local router to transmit information such as 
simple configuration files and description characters that are not easily expressed 
through telephones among terminal users, using the 
send command. It is much 
more convenient than email. Ensuring information security and reliability, the 
terminal message service fulfills information interaction among multiple terminals 
on one router.
For example, user A and user B respectively log into Router A and Router B. If user 
A wants to communicate some information (such as configuration information) 
ServiceFeatures
Echo modeNo local echo
Terminal emulation typeVT100
Baud rateConsistent with interface configuration, 9600 bps by default
Data bitConsistent with interface configuration, 8 bits by default
Parity checkConsistent with interface configuration, no parity by default
Stop bitConsistent with interface configuration, 1 bit by default
Flow controlConsistent with interface configuration, no flow control by 
default
Service Attribute
Enable the function of timeout disconnection from the 
terminal useridle-timeout
Disable the function of timeout disconnection from the 
terminal userundo idle-timeout 
						

							Terminal Message Service59
with user B, user A should telnet onto Router B and execute the send command to 
send the related information in all views. Then user B can receive the “message” 
sent from user A. If user B does not want to receive additional similar messages, 
they can use the 
send switch command to disable the function of receiving 
messages.
Configure Terminal 
Message ServiceTerminal message service configuration includes:
■Send message to terminals
■Enable/disable receiving messages from other terminals
1Configure to send a message to terminals
Perform the following configuration in all view.
Ta b l e 40   Send a message to terminals
Press Ctrl+W to terminate inputting the message, and the system will ask the user 
whether to send the message to all the terminal users:
Send message? [confirm]
Press Enter, Ctrl+W, y, or Y to confirm the sending. Press Ctrl+C or other characters 
to give up the sending.
The terminal message service supports the following features:
■Supports the users that login through Telnet or console port to use the 
message services.
■Supports the input of multiple lines of messages.
■Supports the screen paste on HyperTerminal.
■Supports using the backspace button to modify the message input in a line.
■Does not support the control keys such as Insert, Delete, ↑, ↓, ←, →, Home, 
End, and Ta b.
■Displays the prompt information when users input ?, h or H.
2Enable/disable receiving messages from other terminals
In the terminal message service, receipt of messages from other terminals is 
determined by the 
send switch command. If the terminal message service is 
currently enabled, it will be disabled after a second input of this command.
Perform the following configuration in all views.
Ta b l e 41   Enable/disable receiving messages from other terminals
By default, the terminal message service is enabled to receive messages from other 
terminals
Display Terminal 
Message ServicePerform the following configuration in all views.
Ta b l e 42   Display the terminal message service
OperationCommand
Send a message to all the terminalssend 
OperationCommand
Enable/disable receiving messages from other terminalssend switch
OperationCommand 
						

							60CHAPTER 4: TERMINAL SERVICE
Typical Example of 
Terminal Message 
Service Configuration#  Input the send command in system view.
[Router] send
Enter message, end with CTRL/Z; abort with CTRL/C:
#  Input the contents of the message that the terminal will send.
hello world #  (Enter  to terminate the message input )
end message? [confirm]
Press Enter, Ctrl+W, y, or Y to confirm the sending. Press Ctrl+C or other characters 
to give up the sending.
Dumb Terminal 
Service When the asynchronous serial port (such as synchronous/synchronous serial port, 
AUX port) of the router operates in flow mode, the command line interface (CLI) 
of the router can be used to carry out configuration of the router. This is achieved 
by directly connecting the RS-232 serial port with the asynchronous serial port of 
the router. This is called the dumb terminal operation mode.
As shown in the diagram below, the user can connect with any asynchronous 
serial port and log in to the router by running the hyper terminal on PC to carry 
out the configuration management of the router.
Figure 26   Configuration management through dumb terminal
The typical method of terminal access is:
■The asynchronous port working under the flow mode is connected to the 
RS-232 serial port via dedicated line to enter the router command line interface 
thereby providing another mode of configuring routers besides the mode of 
console port and Telnet mode.
■Based on the dumb terminal, other applications can be built, for instance, 
logging on to other equipment by executing the Telnet command. 
Configure Dumb 
Terminal ServiceFollow these steps to configure a dumb terminal service.
1Configure dumb terminal service
For the synchronous/asynchronous serial port, physical-mode async, async mode 
flow
, and undo modem should be set first.
Perform the following configuration in the interface view.
Ta b l e 43   Configure dumb terminal service
Display the current status of terminal message servicesend status
RS232 Serial Port
Asynchronous Port Quidway Series Router
PC
OperationCommand 
						

							Dumb Terminal Service61
By default, no dumb terminal service is configured.
2Configure auto-execute command command
If the auto-execute command command is configured on the asynchronous serial 
interface, when you press Enter twice on the external terminal connected to the 
interface or log onto the router in modem dial-up mode and press Enter twice, the 
router will automatically execute the operation preset by the 
auto-execute 
command
 command.
If the router is configured with the auto-execute command command, you will 
not be allowed to log into the configuration interface of the router. If the 
command cannot be executed, you will return to the interface with the prompt 
Press ENTER to get started, and after you press Enter, the command will be 
executed.
Please perform the following configurations in asynchronous serial interface view.
Ta b l e 44   Configure auto-execute command command
By default, the auto-execute command command is not configured.
Configuration Examples 
of Dumb Terminal 
ServiceConfigure Dumb Terminal
■The configuration procedure of the dumb terminal on sync/async serial 0 ports 
is as follows:
[Router-Serial0] physical-mode async
[Router-Serial0] undo modem
[Router-Serial0] async mode flow
■The configuration procedure of the dumb terminal on 8/16 async serial 0 port 
is as follows:
[Router-Async0] undo modem
[Router-Async0] async mode flow
■The configuration procedure of the dumb terminal on AUX port is as follows:
[Router-Aux0] undo modem
After the above operation, Press ENTER to get started displays on the terminal 
connected to this async interface, press Enter twice to enter the router 
configuration interface. During the configuration, you can click logout to exit the 
command line interface and can also click Enter twice to return.
Configure Auto-execute command
The user can use the Telnet command specified by the auto-execute command to 
log on the remote SCO UNIX workstation after establishing the connection with 
the Router via the dumb terminal.
Configure the synchronous/asynchronous serial work in 
asynchronous modephysical-mode async
Configure the serial interface of the router to be in flow 
modeasync mode flow
Forbid modem to dial in or dial outundo modem
OperationCommand
Configure the auto-execute command 
command on the asynchronous serial interfaceauto-execute command command
Remove this commandundo auto-execute command 
command 
						

							62CHAPTER 4: TERMINAL SERVICE
Figure 27   Dumb terminal networking diagram
1Configure the interface to dumb terminal mode. 
[Router-Serial1] physical-mode async
[Router-Serial1] undo modem
[Router-Serial1] async mode flow
2Configure the auto-execute command command.
[Router-Serial1] auto-execute command telnet 10.110.164.45
After the configuration, press Enter twice on the terminal connected to this async 
interface to log on the SCO UNIX host 1.110.164.45. During the configuration, 
you can click exit to exit the command line interface and can also click Enter twice 
to return.
Terminal Service of 
Telnet Connection
Telnet OverviewTelnet protocol, which belongs to the application layer protocol in the TCP/IP 
protocol suite, describes how to provide telnet and virtual terminal functions via 
the network. Telnet connection services provided by the 3Com Router 1.x include:
■Telnet Server service: provides services for local and remote users to logon to 
the router, maintains the router and accesses network resources. As shown in 
the following figure, users can logon to the router by running the Telnet client 
program on the computer and perform the configuration management for the 
router.
Figure 28   Telnet server service
■Telnet Client service: provides service for local or remote users who have logged 
on to the local router to access other remote system resources by using the 
Telnet Client program of the local router. As shown in the following figure, 
users can re-logon to router B using the Telnet command and perform 
configuration management after establishing a connection with router A via 
the terminal emulator or Telnet program on the computer.
 Quidw ay  Series Router
10.110. 164.4
4
TerminalSC O U NIX
Workstation10.110.164.4
5
Workstation
(Telnet Client)Router
(Telnet Server) 
						

							Terminal Service of Telnet Connection63
Figure 29   Telnet client service
Reverse Telnet OverviewReverse Telnet service: the user logs on the router with a specified port number by 
running the Telnet client program on the PC. Then the connection to the serial 
port device connected with the async port of the router is established. One 
example: the 3Com Router performs remote configuration and maintenance of 
the external devices connected with its 8/16 asynchronous port with Reverse 
Telnet service. 
Figure 30   Reverse Telnet service
Connection 
Configuration of Telnet 
and Reverse TelnetTerminal Service Features of Telnet Connection
The terminal service features of Telnet connection are shown in the following 
table, and the parameters of the Telnet Client program running on the computer 
should be set according to the table.
Ta b l e 45   Terminal service features of telnet connection
Establish Telnet Connection
Please use the following commands on the Telnet Client program of the host and 
in r system view.
WorkstationRouter A
(
Telnet Client)Router B
( Telnet Server)
Quidway Router
Telnet C lient
M odemO ther c ommunic ation
dev ic es LA N  S w itch
Router
NA S
ServiceValue
Input modeCharacter mode
Echo modeNo local echo
Terminal typeVT100 
						

							64CHAPTER 4: TERMINAL SERVICE
Ta b l e 46   Establish Telnet Server or Telnet Client connection
By default, Telnet Server starts automatically. The default value of service-port is 
23.
To terminate Telnet service, enter Ctrl+] at Telnet Client side.
Setup Reverse Telnet Connection
Please use async mode flow and undo modem commands in asynchronous 
interface view, use 
telnet and terminal telnet refuse-negotiation 
commands in system view, use 
reverse-telnet disconnect, reverse-telnet 
timeout
, reverse-telnet listenport and reverse-telnet return-deal 
commands in interface view.
Ta b l e 47   Enable Reverse Telnet connection
By default, the option for negotiation towards the Telnet client is enabled, and 
Reverse Telnet will expire in 600 seconds. Reverse Telnet transparently transmits all 
data. The interface use the default listen port number.
Reverse Telnet timeout ensures that if no data is transmitted during a specified 
time, the established Reverse Telnet will disconnect automatically. By default, no 
timeout is configured for the Reverse Telnet, that is, as long as the Reverse Telnet is 
connected, even if there is no data being transmitted, the Reverse Telnet will not 
be disconnected.
The Reverse Telnet can be disconnected in interface view.
The undo modem command must be used to disable modem calling-in and 
calling-out before the Reverse Telnet timeout of the configuration interface is 
configured.
On the 3Com Router series, the maximum number of Reverse Telnet connections 
is related to the interface card and the maximum number of tasks supported by 
the router.
OperationCommand
Enable the Telnet Client connection servicetelnet host-ip-address [ 
service-port ]
OperationCommand
Forbid the modem to dial in or dial outundo modem
Set the router to flow mode async mode flow
Log onto the router at specified port and 
connect to corresponding async porttelnet host-ip-address 
service-port 
Disable/Enable the option negotiation towards 
the Telnet clientterminal telnet 
refuse-negotiation
Configure the timeout of Reverse Telnetterminal telnet timeout
Configure the Reverse Telnet timeout of the 
interfacereverse-telnet timeout time
Disconnect the Reverse Telnet of the interfacereverse-telnet disconnect
Do not send the carriage return received from 
the telnet end to the terminalreverse-telnet return-deal 
from-telnet
Do not send the carriage return received from 
the terminal to the telnet endreverse-telnet return-deal 
from-dumb   
						

							Terminal Service of Telnet Connection65
The interface listen port number is within the range of 1025 to 65535. Please note 
that the listen port number cannot be the same as that of the widely used ports. 
By default, the port number and asynchronous interface have the following 
relations:
■The async serial interface number starts from 2001. For instance, the first async 
serial interface number is 2001, the second is 2002, and so on.
■The AUX interface number is 3000. 
■The sync serial interface number starts from 3001. For instance, the first sync 
serial interface number is 3001, the second is 3002, and so on.
Force shut down Telnet Process
In some cases (such as usage of Telnet by a malicious user), the administrator user 
logging from the Console port can use the 
kill telnet command to disconnect 
the link from the Telnet user to the router or disconnect the link according to the 
process number found through the 
display client command. Use caution 
when executing this command.
Please perform the following configuration in system view.
Ta b l e 48   Force to shut down Telnet process
Display and Debug 
Reverse Telnet 
ConnectionPerform the following configuration in all views.
Ta b l e 49   Establish Telnet Server or Telnet Client connection
display client can only be used to display the interface through which the 
Telnet client connected to the router passes. If you want to view the IP address of 
the Telnet server connected to the router, you should execute the 
display tcp 
status
 command. The TCP connection whose local port number is 23 is the Telnet 
connection, including the Telnet client connection and Telnet server connection.
Typical Configuration 
Example of Telnet and 
Reverse Telne
t
Example of Telnet
In the networking diagram shown in Figure 28 “Telnet server service”, the host 
establishes connection with router A (IP address 10.110.0.1), then logs on and 
configures router B (IP address 129.102.0.1).
1Execute the following commands on the user host and Telnet to Router A.
C:\WINDOWS>Telnet 10.110.0.1
2Execute the following commands in the popup Telnet window, and log onto 
Router B.
[RouterA]telnet 129.102.0.1
Trying 129.102.0.1 ...(use CTRL + C to break) 
Connected to 129.102.0.1 
Service port is 23 . 
Username:guest 
OperationCommand
Force to shut down Telnet processkill telnet { all | userID userid }
OperationCommand
Display information of Telnet clients display client
Display information of Telnet connectiondisplay tcp status 
						

							66CHAPTER 4: TERMINAL SERVICE
Password: 
User guest logged in . 
3The message showing successful Telnet to Router B should pop up and display the 
host name of RouterB.
[RouterB]
Example of Reverse Telnet
The host is connected to the router, then communicates with the device 
connected to the seventh asynchronous serial interface of the router. The IP 
address of the router is 10.110.164.44.
[Router] telnet 10.110.164.44 2007
Trying  10.110.164.44...
Service port is 2007 (tty)
Connected to 10.110.164.44
After successful Reverse Telnet, host name of RouterB will be displayed.
[RouterB]
The host can send commands to communicate with the device connected to the 
asynchronous serial interface. If a modem is connected to the interface, you can 
detect the modem status or configure the modem by using the AT command.
Rlogin Terminal 
ServiceRlogin (Remote Login) is one of the most common Internet applications developed 
by the BSD UNIX system, in which a client is connected with the server by TCP 
connection. It provides the function of several remote terminals accessing the 
UNIX host. Rlogin originated from Berkeley UNIX and id used for telnet service 
between UNIX systems. Compared with Telnet protocol, it is easier to implement 
and use Rlogin protocol.
The 3Com Router implemented by Rlogin is Client-based. Rlogin Client enables 
3Com Router series to have functions similar to that of a multi-serial port card, i.e., 
digital or analog terminals that log onto routers through the terminal access 
functionality and can use Rlogin protocol to log onto a remote UNIX host. 
Figure 31   Connect Unix Server and Terminal through the 3Com Router
The Rlogin client provided by the 3Com Router series has the following features:
Quidway Router
Unix Server
...
TerminalTerminal Terminal