1) FLASH ( default location)
2)TFTP server
3)ROM ( used when no other source is found )
Boot process of a router :
When you turn on the router ,POST ( Power-On Self Test) checks the router's hardware,if the system is OK,LED is on.The router checks the configuration register and finds out the location from where IOS image can be loaded.
0*2102 setting means it uses the information from start-up config file to locate the IOS image.If start-up config file is missing it checks 3 locations to locate IOS image.
1) FLASH ( Default Location)
2) TFTP server
3) ROM ( used when no other source is found )
NOTE : configuration file is loaded from
1) NVRAM ( start-up configuration file)
2)TFTP Server
The router loads configuration file into RAM which configures the router.
If configuration file is not found ,router starts setup mode.
In conclusion:
configuration file ( from NVRAM ,TFTP server) to RAM and if it is missing router starts set-up mode
start-up config file information gives IOS image location and if it is missing it checks
1) FLASH ( Default Location)
2) TFTP server
3) ROM ( if no other source is found )
2) WHY NETWORK ADMINISTRATOR WOULD USE CDP ?
CDP (CISCO DISCOVERY PROTOCOL) is used to find out
1) protocol of neighboring devices
2) platform used
3) interface used
CDP (CISCO DISCOVERY PROTOCOL) is
1) an intermediate media protocol
2) runs on all cisco devices like routers,bridges,switches etc.
3) works on layer 2
NOTE : multicast advertise is sent to 01-00-0 c-cc-cc-cc as destination address in every 60 seconds.
on every 180 seconds hold time,if neighboring devices advertise is not received,then the information of neighboring devices will be cleared.
So,network administrator would use CDP :
1) to verify layer 2 connectivity of two devices when layer 3 fails
2) to identify the ip address of connected devices ( to telnet)
commands used are :
show cdp neighbor
show cdp neighbor details
3)WHAT HAPPENS WHEN CHANGING CONFIGURATION REGISTER TO 0*2142 ?
0*2142 setting ignores NVRAM configuration entries and router will prompt to enter the initial configuration mode.
4) Quality of Service (QoS) prioritize the traffic and more important traffic passes first. Debug command is used to show the effect on real time.
5) COMMAND USED TO DEBUG A PING COMMAND
debug ip icmp
6) COMMAND USED TO DISPLAY CPU UTILIZATION
show process ( or " show processes" in full )
The output of this command gives lots of information about each processes.
7) COMMAND USED TO REVEAL THE LAST COMMAND METHOD USED TO POWER-CYCLE A ROUTER
show version
8)TERMINAL MONITOR
By default CISCO IOS doesn't send log messages to a terminal session over IP like Telnet,SSH.To display the debug command output and error messages ,the command " terminal monitor " is used.
but console connection do have logging feature enabled.
In short,CISCO IOS have no logging feature and the command " terminal monitor " is used.to display
and console connection have logging feature enabled.
9)
In above figure, core and core2, are both catalyst 2950s and the addressing scheme is as
Router Ethernet port - 1st usable address
core-second usable address
core2 -third usable address
The commands used at core2 so that it can be managed remotely from any subnet on the network are
core2 (config)# interface vlan 1
core2 (config-if)# ip address 192.168.1.11 255.255.255.248
core2(config)# line vty 0 4
core2(config-line)# password cisco
core2(config)# ip default-gateway 192.168.1.9
10) BACKING UP AN IOS IMAGE TO TFTP SERVER
In order to back up IOS image to TFTP server,the first step is to make sure it is reachable to router,second step is to check it has adequate space to load IOS image and third step is to verify file naming and path requirements.
11) TRACEROUTE COMMAND
traceroute command shows the path a packet will take to reach to the destination address.
12)
In above figure,there are only 2 cisco devices and the serial network between 2 devices has the mask of 255.255.255.252.Given the output the following statements are true
1) The London router is a cisco 2310
2) The Manchester serial address is 10.1.1.1
3) The CDP information was received on port Serial0/0 of the Manchester Router.
13) ROMMON MODE
If the cisco router boots in rommon mode it means,
the configuration register is set to xxx0(the boot field-4th bit -0)
The router is unable to locate IOS image ( use " dir flash " to find out IOS in flash and try to boot that flash with "boot flash:<IOS image>")
If the IOS image is corrupted,copy it from TFTP server ( use "tftpdnld" )
14)
In above output it is seen that administrator erased the flash before copying by pressing enter.
For not enough space availabe system delivers error message like
%Error copying tftp://192.168.2.167/c1600-k8sy-mz.123-16a.bin (Not enough space on device)
15)
In above it is seen that configuration register is 0*2102 ,this means it try to load IOS image from flash first,but line System image file is "tftp://172.16.1.129/hampton/nitro/c7200-j-mz" tells us that IOS image is loaded from tftp server because it couldn't load IOS image from flash.
16) COMMANDS USED TO DETERMINE A CISCO ROUTER CHASSIS SERIAL NUMBER
1) show inventory
2) show diag
17) COMMAND USED TO MANAGE MEMORY BY DISPLAYING FLASH MEMORY AND NVRAM UTILIZATION
1) show file systems
18)
This means SSH protocol is used via the virtual terminal ports.
19) COMMAND TO PERMIT SSH AND TELNET ACCESS TO A CATALYST
1) transport input all
20)
The network administrator run show cdp neighbors at R2 then entries from R1 and SW-B are displayed.
21)
User exec mode is limited to basic monitoring command
privileged exec mode provides access to all other router commands
commands in global configuration mode affect the entire system
commands in specific configuration mode affect the interfaces/processes only
set up mode is for interactive configuration dialog
