Cisco notes 101

cdp timer   10  -> how often cdp packet transmited out all active interface.  (19sec)
cdp holdtime 5  -> amount time device wil hold packet received from neighbor address.  (5 sec)


no cdp run -> turn off cdp all interface
no cdp enable-> turn off cdp neihgboor on one interface
cdp enabl.



show cdp neighbor          -> show list devices directly connected neighbor
show cdp *                 -> show all directly connected information
show cdp * protocol        -> check directly connected device IP ADDRESS
show cdp entry * version   -> list all directly connected devices
show cdp traffic           -> check traffic!


show cdp interface         -> check interface status



from show running config we can get ip information!
from cdp neighbor we can mapping directly connected devices!


^ best tool for information gathering.
^ can create topology!




!! how to configure telnet !!

activate telnet on router:

- conf t
- line vty 0 807
- password telnet
- login
- ^Z




ctrl+shift6+x    ->  back to original router but keep session alive.
enter twice      ->  back to remote router ( after ctrl + shift +  6 )

#show session -> checking session ( who logged on to this device)




----------------------
no ip domain-lookup      -> disable ip domain lookup  ( if wrong input command cisco will search from dns ).
ip domain-lookup         -> enable ip domain lookup
ip name-server 192.168.10.1    -> setting domain server
ip domain-name toro.com       -> appends domain name to host name  (FQDN)
sh hosts                     -> check domain and check domain cached information from host table


---------------------



debug all -> turn on debug all ( turn debug all on ->> carefull with high traffic router / switch  as it can make the device hang up :) )
no debug all -> turn off all
debug ip rip ->  debug rip




^ proceed with caution!!   check router utilization first!   using command:

show process -> showing process. ( if cpu utilization 50% ++ carefull to turn debug all).

Cisco configuration Register

Im recently graduated from my bachelor degree study. Now im working as Network Engineer at one of biggest cisco gold partner in indonesia. If any of u know Multipolar thats where i make some progress in my career.

Im responsible in managing biggest local bank indonesia network distribution switch, access, wireless, video conference and nexus for SOSA application, and datacenter.  

Below is some note / documentation that maybe useful for u guys.

 

Cisco Configuration Register

All cisco router have  16 bit software register that is written on NVRAM.

By default the configuration register is set to load IOS from flash memory and look for and load startup-config file from NVRAM.

there are many useful of cisco configuration register. One of them is to enter ROM monitor mode to recover cisco password.

first we need to know our cisco configuration register by typing command:

# show version.

Configuration Register is 0x2102     ->  find this line.   ( default setting )

!!to change the configuration register!!

#conf terminal

(config)#config register 0x2142          -> change register 

(config)#end

#wr                                                      -> save config

#reload                                                -> reload router to apply new configuration register.

to recover password on cisco router:

1 boot router

2 while boot perform break to enter router into ROM monitor mode.

3 change register to 0x2142

4 reload router

5 enter privileged mode

6 copy startup-config running-configuration

7 change password

8 reset configuration regiter using default value (0x2102)

9 save and reload

there are other purpose of changing configuration register as:

• select boot source
• control broadcast address
• set terminal baud rate
• enable booting from TFTP server
• disable / enable break button

done.