Filter on our cisco router ports right to protect our servers is an essential duty. In the example below how to filter the only port ssh:

• at the console enter the command:
• enable
• Then enter the password.
• hours to give a look to the configuration in use with the command:
• show running-config
• Take vision of the interfaces that you want to filter (in our example will be a serial)
• hours enter the command:
• config ends
• Following the commands needed to make an access list named minimal but functional 101:
• access-list 101 permit tcp any any established
• access-list 101 deny tcp 212.69.128.0 0.0.0.255 any eq 22 log
• access-list 101 permit ip any any
• our access list that is pretty ready. now we must go to our interface:
• interface serial1/1.1
• and then activate the access list you want with the following command:
• ip access-group 101 in
• voila, you're done, given that if something goes wrong you will go over even a package, you can always restart the router. If everything smoothly row then you have to do is give the commands:
• write
• ctrl + z
• prorpio and if you want before you leave, you can look at the statistics the access list:
• show access-list

To get to this extreme synthesis we must pass through broader horizons, at this link you can find the know-how from which I fed to cisco router to filter at least part of what it should.

Here are the steps to reset a cisco router (tested on series 800 and 1800):

1. Connect the console cable (the blue ribbon cable) to the serial PC on one side and the router console port
2. Turn on the router
3. Within the first 30 seconds you enter the sequence of break in the window of the terminal (HyperTerminal Ctrl-Break or Ctrl-F6-Break, Ctrl-a minicom f). Ctrl + C or Ctrl + Stop, or Ctrl + Del
4. If you completed the previous step you are in the rom monitor prompt, and should dartene confirmation showing rommon 1>
5. confreg 0 × 2142 <ENTER>
6. reset <ENTER>
7. At this point the route ignoring restart the configuration correntementein use
8. Answer no to the request to enter setup mode
9. ena <ENTER> or enable <ENTER>
10. copy startup-config running-config <ENTER>
11. Now you have loaded into memory the current configuration of which can not remember your password
12. configure terminal <ENTER>
13. enable secret <nuova_password> <ENTER>
14. config-register 0 × 2102 <ENTER>
15. end <ENTER>
16. The next step is to make permanent changes to the password
17. copy running-config startup-config <ENTER>
18. Now the router has the new password after reboot. Wishing you can change other parameters at this stage, our goal cmq