Telnet configuration command directory
This chapter will introduce telnet and its configurations and
management commands. “telnet” is used to setup “telnet” session with a remote
server. “telnet” is usually used to telnet Unix system.
It needs negotiation about optional
items. “telnet” can not provide authorization to itself . So , it is mostly
different from Rlogin in which it can not provide password verification to
itself.
command format to
create telnet session is following:
telnet server-ip-addr/server-host-name
[/port port][/source-interface interface] [/local
local-ip-addr] [/debug][echo/noecho] [/script scriptname]
parameter:
server-ip-addr:
|
Remote server’s IP address is expressed by decimal
system. |
server-host-name: |
The host name of the remote server, it need use command
“ip host” to configure. |
port: |
The port providing telnet service of the remote server. |
interface: |
Local interface to launch telnet connection |
local-ip-addr: |
Local IP address to launch telnet connection |
/debug: |
Open debug switch of client , print negotiation course
when connection. |
echo/noecho: |
Open/turnoff local echo, default is noecho. |
scriptname: |
The script name used to automatically login |
Default:
port default is 23, interface does not have default.
command mode:
supervisor mode
explanation:
User can use one of following commands to telnet
telnet server-ip-addr/server-host-name
In this condition, application program will transmit telnet
request to 23 interface of the remote server, the used IP address is the nearnest
IP address according to route table.
telnet server-ip-addr/server-host-name /port port
At this time,
application program transmit telnet request to the peer port.
telnet server-ip-addr/server-host-name /source-interface interface
At this time,
application use interface’s IP address as local address.
telnet server-ip-addr/server-host-name /debug
At this time,
application program opens debug switch of client, and will output link
negotiation course.
telnet server-ip-addr/server-host-name echo/noecho
server-ip-addr:
|
Remote server’s IP address is expressed by decimal
system. |
server-host-name: |
The host name of the remote server, it need use command
“ip host” to configure. |
port: |
The port providing telnet service of the remote server. |
interface: |
Local interface to launch telnet connection |
local-ip-addr: |
Local IP address to launch telnet connection |
/debug: |
Open debug switch of client , print negotiation course
when connection. |
echo/noecho: |
Open/turnoff local echo, default is noecho. |
scriptname: |
The script name used to automatically login |
At this time , application program opens/closes local echo.
Usually, Local echo is closed ,echo is finished by the server. Only when the
server is not responsible for echo, local echo switch will open.
telnet server-ip-addr/server-host-name /script scriptname
Before
execute automatically login command of this script , use command “ip telnet
script” to configure.
Above
command parameters can be used united.
When in the course
of session with the remote server ,user can use “q” key to quit .If do not exit
by hand, it will exit after 10 seconds waiting.
Example:
If user want to telnet to the server “ 192.168.20.124”, and the server has
two telnet ports: 23 and 2323, and local has two ports: e1/1(192.168.20.240)
and s1/0(202.96.124.240).User can use following commands to telnet.
1.telnet 192.168.20.124
/port 2323
In such a condition , telnet will
connect to peer 2323 port .The local IP address seen by the peer is
192.168.20.240.
2.telnet 192.168.20.124
/source-interface s1/0
In such a condition, telnet will connect to peer 23
port .The local IP address seen by the peer is 202.96.124.240.
3.telnet 192.168.20.124
/local 192.168.20.240
In such
a condition , telnet will connect to peer 23 port .The local IP address seen by
the peer is 192.168.20.240.
4.telnet 192.168.20.124
/debug
In such a condition, telnet will print
negotiation course to setup telnet connection to peer
23 port.
5.telnet 192.168.20.124
/echo
In such
a condition, telnet will open local echo switch. At his time, if the sever runs
echo also, all input will be echoed for two times.
6.telnet 192.168.20.124
/script s1
Use login script named “s1” to
automatically login.
configuration commands’ format about telnet session are following:
ip telnet source-interface interface
ip telnet access-class
accesslist
ip telnet listen-port
start-port [end-port]
ip telnet script scriptname
‘user_prompt’ user_answer ‘pwd_prompt’ pwd_answer
parameter:
interface: |
The local interface launching telnet |
accesslist: |
When local is receiving connection,
accessing list name to limit source address. |
start-port: |
user appoint the start-port number of
interception field |
end-port: |
user
appoint the end-port number of interception field |
scriptname: |
login script name |
user_prompt: |
user
name prompt information sent back by the telnet server |
user_answer: |
user
answer information submitted by client |
pwd_prompt: |
user
password prompt information sent back by the telnet server |
pwd_answer: |
password
answer information submitted by client |
default
none
command mode
global
configuration mode
explanation
User
can use following commands to configure local source interface to launch
telnet.
ip
telnet source-interface interface
In such
a condition, all subsequent telnet use this interface. This configuration
command is similar to “telnet source-interface interface”, but it does not need
to add parameter when using command ‘telnet”. If not only configure a interface
,but also add interface parameter in command “telnet”, it should be determined
by the latter.
User
can use following commands to configure access list names limited by local
telnet connection.
ip
telnet access-class accesslist
In such
a condition, after that, when the server accepts all telnet connections, it
needs to check access list.
User
can use following commands to configure other interfaces except default (23) to receive telnet connection.
ip telnet listen-port
start-port [end-port]
Explanation: if not appoint end-port number, it will intercept on
a special port. The numbers of appointed interception ports can not be more
than 16,and ports can be limited between 3001 and 3999.
ip telnet script s1
‘login:’ router ‘Password:’ test
Explanation: when
configuring script , user name prompt, answer, password prompt ,answer must
fully match. And user must pay attention to prompt information, it differs
whether capitalization or not, and prompt information must add (‘’). If any
item is not configured properly, it can not automatically login successfully .
Note: above four commands can add prefix “no” to cancel setting.
example
1.ip telnet source-interface s1/0
In such a condition,
all coming launching telnet
connections use s1/0 interface.
2.ip telnet access-class abc
In such a condition, all coming
accepting telnet connections will be checked by access-list “abc”.
3.ip telnet listen-port 3001 3010
Besides 23,user can use all port
between 3001 and 3010 to accept telnet connections.
4.ip telnet script s1 ‘login:’ router
‘Password:’ test
configure a login script named
s1,user name prompt is ‘login:’, answer is router,
password prompt is ‘Password:’,
answer is test.
ctrl-shift-6+x(suspend
current telnet connection)
suspend telnet connection on client
ctrl-shift-6+x
parameter
none
default
none
command mode
any time on current telnet session
explanation
user can use this short key to suspend current telnet connection
from client.
example
RouterA>telnet
192.168.20.1
Welcome to Multi-Protocol 1700
Series Router
RouterB>ena
RouterB#(按ctrl-shift-6+x)
RouterA>
If user press “ctrl-shift-6+x”on current telnet session connection
to RouterB , it will suspend connection to RouterB, and go back to RouterA’s
current state
check current suspend telnet session on client:
where
parameter
none
default
none
command mode
global configration mode
explanation
User can use this command to check current suspend out telnet
connection on client .Displayed information include number, peer address, peer port ,local
address, local port.
note: command ”where” is different from command “show telnet”. The
former is used on client to show out telnet connection, while the latter is
used on server client to show in telnet connection.
example
RouterA>telnet
192.168.20.1
Welcome to Multi-Protocol 1700
Series Router
RouterB>ena
RouterB#(按ctrl-shift-6+x)
RouterA>
telnet 192.168.20.2
Welcome to Multi-Protocol 1700
Series Router
RouterC>ena
RouterC#(按ctrl-shift-6+x)
RouterA>where
NO.
Remote Addr
Remote Port Local
Addr Local
Port
1 192.168.20.1
23
192.168.20.180 20034
2 192.168.20.2
23
192.168.20.180 20035
User input command ”where”on RouterA to show out and suspend
information on RouterA.
resume current out and suspend telnet session on client:
resume no
parameter
no:current suspend telnet session number seen through command “where”
default
none
command mode
global configuration mode
explanation
User can use this command to resume current out and suspend telnet
connection on client.
example
RouterA>telnet
192.168.20.1
Welcome to Multi-Protocol
1700 Series Router
RouterB>ena
RouterB#(按ctrl-shift-6+x)
RouterA>
telnet 192.168.20.2
Welcome to Multi-Protocol 1700
Series Router
RouterC>ena
RouterC#(按ctrl-shift-6+x)
RouterA>where
NO.
Remote Addr
Remote Port Local
Addr Local
Port
1 192.168.20.1
23
192.168.20.180 20034
2 192.168.20.2
23
192.168.20.180 20035
RouterA>Resume
1
[Resuming connection 1 to 192.168.20.73
. . . ]
(enter)
RouterB#
User input command “where”on RouterA, after displaying out and
suspend information on RouterA, input “Resume 1”,displayed information will prompt
user “ resume to connection 1”,
after enter, it will appear: “RouterB#”
clear current suspend out telnet session on client:
disconnect no
parameter
no: current suspend telnet session number through command “where”
default
none
command mode
global configuration state
expanation
User can use this command
to clear current suspend out telnet connection on client.
note: command ”disconnect” is different from command “clear
telnet”. The former is used on client to clear out telnet connection, while the
latter is used on server client to clear in telnet connection.
example
RouterA>telnet
192.168.20.1
Welcome to Multi-Protocol 1700
Series Router
RouterB>ena
RouterB#(按ctrl-shift-6+x)
RouterA>
telnet 192.168.20.2
Welcome to Multi-Protocol 1700
Series Router
RouterC>ena
RouterC#(按ctrl-shift-6+x)
RouterA>where
NO.
Remote Addr
Remote Port Local
Addr Local
Port
1 192.168.20.1
23
192.168.20.180 20034
2 192.168.20.2
23
192.168.20.180 20035
RouterA>disconnect
1
<Closing connection to 192.168.20.1> <y/n>y
Connection closed by
remote host.
RouterA>
User inputs command “where”on RouterA, after displaying out and
suspend information on RouterA, input “disconnect 1”,displayed information will
prompt user “ whether close connection to RouterB”, after enter”Y”, connection closes.
terminal
switch function
it adds terminal switch function in this version telnet. Perform
following steps to use this function:
1)
configure alias (alias command) for command “connect” in global
configuration mode
2)
configure terminal switch key in line configuration mode
(switchkey command)
3)
configure terminal character sequence in line configuration
mode(sequence-char command)(optional, if without this step, screen information
can not be saved.)
4)
configure asynchronous interface to interactive mode(async
command) in interface configuration mode
5)
Connect real terminal to asynchronous interface and open the
terminal
now ,user can switch terminal free by pressing
random configured short keys when operation and can display switch menu by
“ctrl+\”keys.
relevant
command
the commands to configure terminal switch keys on line are
following:
switchkey key cmdalias server-name
parameter:
key: can use “ctrl-a-ctrl-z”, do not use “ctrl-h”
cmdalias: alias of command “connect”
server-name: the remote server’s name, it will appear in switch
prompt information and switch menu
none
line configuration mode
explanation
User can configure terminal
switch keys and their correspond alias and remote host name through using this
command.
note: 1:cmdalias parameter
must appoint to a correct “connect”command
2) “key” parameter can not be “ctrl-h”
3)
“server-name” parameter will appear in switch prompt information and
switch menu
4) do not configure “autocommand” on
this line ,or terminal switch function will not work
example
RouterA>switchkey
ctrl-a cona ServerA
configure switch-key “ctrl-a”, use command alias “cona”, switch to
the server “ServerA”.
the command determining whether to output terminal switch prompt
information on line are following:
switchmsg enable/disable
parameter:
enable: output
terminal switch prompt information
disable:forbid to output terminal switch prompt information
default:
disable
command mode:
line configuration mode
explanation:
User can use this command to configure on line whether to output
switch prompt information when terminal switch.
example:
RouterA>switchmsg
enable
output switch prompt information when terminal switch
the commands to configure switch keys on line are following:
sequence-char key char1 char2 char3 …
parameter:
key: can use “ctrl-a-ctrl-z”, can not configure”ctrl-h”
char1 char2 char3 …: screen sequence-char associated special terminal
default
none
command mode
line configuration mode
explanation:
User can use this command
to configure terminal switch keys and sequence-char on line.
note 1) key parameter can not be “ctrl-h”
2) Sequence-char parameter is associated with specific terminal
,user can search terminal manual to obtain usually.
3) Sequence-char parameter
must be hex number, begins with Ox,
and
distinguish each character with space key.
example
RouterA>sequence-char
ctrl-a 0x1b 0x21 0x38 0x51
sequence-char to configure switch key “ctrl-a” is “0x1b 0x21 0x38
0x5”
Other alias, async commands can refer to related configuration
explanation .
example
The router’s configurations are following:
…
…
...
interface Serial1/1
physical-layer mode
async
no ip
directed-broadcast
async mode
interactive
line tty 1
switchkey
CTRL-U cona ServerA
sequence-char CTRL-U
0x1b 0x21 0x38 0x51
switchkey CTRL-V conb ServerB
sequence-char CTRL-V
0x1b 0x21 0x39 0x51
switchkey CTRL-W conc ServerC
sequence-char CTRL-W 0x1b 0x21 0x31 0x30 0x51
switchmsg enable
…
...
alias cona connect 192.168.20.1
alias conb connect 192.168.20.2
alias conc connect 192.168.20.3
After finish all configurations and connection, open terminal,
switch menu will automatically appear in the screen. The system will switch to
ServerA automatically after entering “CTRL-U”(and output prompt information of
current host ServerA).
The system will switch to ServerB automatically after entering
“CTRL-V”(and output prompt information of current host ServerB).
The system will switch to ServerC automatically after entering
“CTRL-W”(and output prompt information of current host ServerC).
At any time, after entering“CTRL-\”,switch menu will appear in
current screen, and add “*”behind current server.
The following is display content after input “CTRL-\”:
======================================
Terminal Switch Menu
1)
CTRL-U
ServerA *
2)
CTRL-V
ServerB
3)
CTRL-W
ServerC
NOTE:
1)
In the operation of several connections, if exiting from one of
the connections (not switch), system will take the first connection as current
connection, screen will restore to the first host’s interface, if the first
connection is exiting , system will take the second connection as current
connection, screen will restore to the second host’s interface.
2)
after finish all tasks, the suggested way to exit the system is
to close terminal directly regardless how many connections are open curremtly.
3)
do not exit the first connection before exiting other
connections
4)
user had better not exit some connection in the operation, and
only switch. To close the terminal after finish all operations.
5)
in the operation of terminal switch, the functions of
connections suspending and restoring through ctrl-shift-6+x will be forbidden.
the command format to clear telnet session on the server is
following:
clear telnet no
parameter
no: the telnet
session number displayed by show telnet
default
none
command mode
supervisor mode
explanation:
User can use this command to clear telnet session on the server.
example
1. clear telnet 1
clear
telnet 1 seesion (192.168.20.220:1097) on the server
the command format to show telnet session of the server is
following:
show telnet
parameter
none
default
none
command mode
other modes except user mode
explanation:
User can use this command to show telnet session of the server.
The displayed information include number, peer address, peer port, local
address, local port.
example
1. show telnet
Display
connect-in telnet session information of the server.
perform
results are following:
NO. Remote Addr Remote Port Local Addr Local Port
1
192.168.20.220
1097
192.168.20.240
23
2
192.168.20.180 14034
192.168.20.240
23
command”debug”’s format of telnet session is following:
debug telnet
parameter
none
default
none
command mode
supervisor mode
explanation:
User can use this command to open telnet’s debug switch.
Now, all connect-in telnet session’s negotiation course print in
debug output windows.
This command is different from telnet command with debug parameter
in: the former is output connect-in telnet session’s debug information of the
server, the latter is output launching telnet session’s debug information of
the client.
example
debug telnet
User
open connect-in telnet session’s debug of the server.