Chabot College
ELEC 99.08
telnet
CISCO NETWORKING ACADEMY
telnet
• Uses services of Layers 7 - 1
CISCO NETWORKING ACADEMY
telnet
• Functions:
– Tests layers 7 - 1
– Remote access over the network to virtual
terminal console of router.
Useful for remote administration.
CISCO NETWORKING ACADEMY
telnet
• Listener:
– by default, hosts “listen” on port 23
– telnet listener called “daemon” on unix,
“service” on NT
– Cisco routers listen for telnet on port 23
– telnet login should be controlled with
password.
CISCO NETWORKING ACADEMY
telnet
• When you telnet to a remote router, your screen
shows the remote router’s prompt:
hayward# telnet fremont
trying 10.2.0.1…open
User access verification
Password:
fremont>
hayward
CISCO NETWORKING ACADEMY
fremont
telnet
• When you exit your telnet session on a remote
router, you return to the previous router’s
prompt:
hayward# telnet fremont
trying 10.2.0.1…open
User access verification
Password:
fremont> exit
hayward#
hayward
CISCO NETWORKING ACADEMY
fremont
telnet - out & back
• As you telnet from ‘hayward’ to other routers,
you can return to your “home” router each time:
hayward
oakland
sanfranciso
home router
telnet to oakland
oakland
hayward
sanfranciso
exit oakland
hayward
oakland
telnet to sanfranciso
CISCO NETWORKING ACADEMY
sanfranciso
telnet - daisy chain
• As you telnet from router to router, you can
“daisy chain” your sessions:
hayward
oakland
sanfranciso
home router
telnet to oakland
hayward
oakland
sanfranciso
telnet to sanfranciso
CISCO NETWORKING ACADEMY
telnet - daisy chain
• As you you exit, you will return one hop at a
time along the chain:
hayward
oakland
sanfranciso
home router
telnet to oakland
oakland
hayward
sanfranciso
telnet to sanfranciso
hayward
oakland
sanfranciso
exit sanfrancisco
oakland
hayward
CISCO NETWORKING ACADEMY
exit oakland
sanfranciso
IOS telnet Commands
• To telnet to another router, use any of these:
hayward# telnet 10.0.2.1
hayward# connect 10.0.2.1
hayward# 10.0.2.1
hayward
CISCO NETWORKING ACADEMY
10.0.2.1
IOS telnet Commands
• You may also use host names, but only if
– DNS services are running and enabled, or
– your router has an IP host table in its config
hayward# telnet fremont
hayward# connect fremont
hayward# fremont
hayward
CISCO NETWORKING ACADEMY
fremont (10.0.2.1)
IOS telnet Commands
• To exit your telnet session and return to the
previous router’s prompt, use any of these:
fremont> exit
hayward#
fremont> logout
hayward#
hayward
CISCO NETWORKING ACADEMY
fremont
telnet - exit
• Be sure to exit your telnet session when done!
• Don’t just close your hyperterm session and
leave yourself connected to the remote router.
If you don’t exit, the VTY port you were using
will remain busy and unusuable by other
students.
• Remember, there are only 5 VTY ports!
fremont> exit
hayward#
CISCO NETWORKING ACADEMY
telnet practice - Router e_SIM
Try it now with Router e-SIM:
– Start Router e-SIM
– Give all your routers a configuration:
• click SHOW DONE
• in the row of SET buttons at the bottom, click A, B, C, D, E
• click HIDE DONE
– Login - Password - cisco
Limitations: Router e-SIM understands only these commands:
– telnet xxx.xxx.xxx.xxx (IP Address)
– exit
CISCO NETWORKING ACADEMY
telnet practice - Router e_SIM
• Try these, in order:
Lab_A>
Lab_B>
Lab_A>
Lab_C>
Lab_A>
Lab_E>
telnet 201.100.11.2
exit
telnet 199.6.13.2
exit
telnet 210.93.105.2
exit
Lab_A>
Lab_B>
Lab_C>
Lab_D>
Lab_E>
Lab_D>
Lab_C>
Lab_B>
Lab_A>
telnet
telnet
telnet
telnet
exit
exit
exit
exit
CISCO NETWORKING ACADEMY
201.100.11.2
199.6.13.2
204.204.7.2
210.93.105.2
Out & back
Daisy chain