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#1: The "?"
It may seem entirely too obvious that you should know how to type ? to ask for help when using
the Cisco IOS. However, the Cisco IOS is completely different from other operating systems
when it comes to using the question mark (help key). As the IOS is a command-line operating
system with thousands of possible commands and parameters, using the ? can save your day.
You can use the command in many ways. First, use it when you don't know what command to
type. For example, type ? at the command line for a list of all possible commands. You can also
use ? when you don't know what a command's next parameter should be. For example, you
might type show ip ? If the router requires no other parameters for the command, the router will
offer <CR> as the only option.
Finally, use ? to see all commands that start with a particular letter. For example, show c? will
return a list of commands that start with the letter "c".
#2: show running-configuration
The show running-config command shows the router, switch, or firewall's current configuration.
The running-configuration is the config that is in the router's memory. You change this config
when you make changes to the router. Keep in mind that config is not saved until you do a copy
running-configuration startup-configuration. This command can be abbreviated sh run.
SEE: Server deployment/migration checklist (Tech Pro Research)
#3: copy running-configuration startup-configuration
This command will save the configuration that is currently being modified (in RAM), also
known as the running-configuration, to the nonvolatile RAM (NVRAM). If the power is lost, the
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NVRAM will preserve this configuration. In other words, if you edit the router's configuration,
don't use this command and reboot the router—those changes will be lost. This command can be
abbreviatedcopy run start. The copy command can also be used to copy the running or startup
configuration from the router to a TFTP server in case something happens to the router.
#4: show interface
The show interface command displays the status of the router's interfaces. Among other things,
this output provides the following:
• Interface status (up/down)
• Protocol status on the interface
• Utilization
• Errors
• MTU
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This command is essential for troubleshooting a router or switch. It can also be used by
specifying a certain interface, like sh int g0/0.
#5: show ip interface
More about Networking
Even more popular than show interface are show ip interface and show ip interface brief.
The show ip interface command provides tons of useful information about the configuration and
status of the IP protocol and its services, on all interfaces. The show ip interface brief command
provides a quick status of the interfaces on the router, including their IP address, Layer 2 status,
and Layer 3 status.
#6: config terminal, enable, interface, and router
Cisco routers have different modes where only certain things can be shown or certain things can
be changed. Being able to move between these modes is critical to successfully configuring the
router.
For example, when logging in, you start off at the user mode (where the prompt looks like >).
From there, you type enable to move to privileged mode (where the prompt looks like #). In
privileged mode, you can show anything but not make changes. Next, type config
terminal (or config t) to go to global configuration mode (where the prompt looks like
router(config)# ). From here, you can change global parameters. To change a parameter on an
interface (like the IP address), go to interface configuration mode with the interface command
(where the prompt looks like router(config-if)#). Also from the global configuration mode, you
can go into router configuration using the router {protocol} command. To exit from a mode,
type exit.
#7: no shutdown
The no shutdown command enables an interface (brings it up). This command must be used in
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interface configuration mode. It is useful for new interfaces and for troubleshooting. When
you're having trouble with an interface, you may want to try a shut and no shut. Of course, to
bring the interface down, reverse the command and just say shutdown. This command can be
abbreviated no shut.
#8: show ip route
The show ip route command is used to show the router's routing table. This is the list of all
networks that the router can reach, their metric (the router's preference for them), and how to get
there. This command can be abbreviated sh ip ro and can have parameters after it, like sh ip ro
ospf for all OSPF routes. To clear the routing table of all routes, you do clear ip route. To clear
it of just one routes, issue the command clear ip route x.x.x.x (where x.x.x.x is the network you
want to clear).
TO SCORE A RATED A+
#1: The "?"
It may seem entirely too obvious that you should know how to type ? to ask for help when using
the Cisco IOS. However, the Cisco IOS is completely different from other operating systems
when it comes to using the question mark (help key). As the IOS is a command-line operating
system with thousands of possible commands and parameters, using the ? can save your day.
You can use the command in many ways. First, use it when you don't know what command to
type. For example, type ? at the command line for a list of all possible commands. You can also
use ? when you don't know what a command's next parameter should be. For example, you
might type show ip ? If the router requires no other parameters for the command, the router will
offer <CR> as the only option.
Finally, use ? to see all commands that start with a particular letter. For example, show c? will
return a list of commands that start with the letter "c".
#2: show running-configuration
The show running-config command shows the router, switch, or firewall's current configuration.
The running-configuration is the config that is in the router's memory. You change this config
when you make changes to the router. Keep in mind that config is not saved until you do a copy
running-configuration startup-configuration. This command can be abbreviated sh run.
SEE: Server deployment/migration checklist (Tech Pro Research)
#3: copy running-configuration startup-configuration
This command will save the configuration that is currently being modified (in RAM), also
known as the running-configuration, to the nonvolatile RAM (NVRAM). If the power is lost, the
,CNE THEORY DOCUMENT Q & A DOWNLOAD
TO SCORE A RATED A+
NVRAM will preserve this configuration. In other words, if you edit the router's configuration,
don't use this command and reboot the router—those changes will be lost. This command can be
abbreviatedcopy run start. The copy command can also be used to copy the running or startup
configuration from the router to a TFTP server in case something happens to the router.
#4: show interface
The show interface command displays the status of the router's interfaces. Among other things,
this output provides the following:
• Interface status (up/down)
• Protocol status on the interface
• Utilization
• Errors
• MTU
,CNE THEORY DOCUMENT Q & A DOWNLOAD
TO SCORE A RATED A+
This command is essential for troubleshooting a router or switch. It can also be used by
specifying a certain interface, like sh int g0/0.
#5: show ip interface
More about Networking
Even more popular than show interface are show ip interface and show ip interface brief.
The show ip interface command provides tons of useful information about the configuration and
status of the IP protocol and its services, on all interfaces. The show ip interface brief command
provides a quick status of the interfaces on the router, including their IP address, Layer 2 status,
and Layer 3 status.
#6: config terminal, enable, interface, and router
Cisco routers have different modes where only certain things can be shown or certain things can
be changed. Being able to move between these modes is critical to successfully configuring the
router.
For example, when logging in, you start off at the user mode (where the prompt looks like >).
From there, you type enable to move to privileged mode (where the prompt looks like #). In
privileged mode, you can show anything but not make changes. Next, type config
terminal (or config t) to go to global configuration mode (where the prompt looks like
router(config)# ). From here, you can change global parameters. To change a parameter on an
interface (like the IP address), go to interface configuration mode with the interface command
(where the prompt looks like router(config-if)#). Also from the global configuration mode, you
can go into router configuration using the router {protocol} command. To exit from a mode,
type exit.
#7: no shutdown
The no shutdown command enables an interface (brings it up). This command must be used in
, CNE THEORY DOCUMENT Q & A DOWNLOAD
TO SCORE A RATED A+
interface configuration mode. It is useful for new interfaces and for troubleshooting. When
you're having trouble with an interface, you may want to try a shut and no shut. Of course, to
bring the interface down, reverse the command and just say shutdown. This command can be
abbreviated no shut.
#8: show ip route
The show ip route command is used to show the router's routing table. This is the list of all
networks that the router can reach, their metric (the router's preference for them), and how to get
there. This command can be abbreviated sh ip ro and can have parameters after it, like sh ip ro
ospf for all OSPF routes. To clear the routing table of all routes, you do clear ip route. To clear
it of just one routes, issue the command clear ip route x.x.x.x (where x.x.x.x is the network you
want to clear).
