Passing The Cisco CCNA Exam: An Illustrated Guide To Router Modes

When you're getting started on your CCNA studies, learning the different router modes is key to passing your Intro and ICND exams. But keeping those modes straight can be very difficult. (At least it was for me!) Let's take a look at the various router modes you'll need to know about to pass your CCNA, and use IOS Help to illustrate the different uses of each mode.

The first mode you'll see on a router (if the person before you logged off as they should have) is user exec mode. This is also the default mode a user is placed into when using Telnet to connect to a router. The prompt will look like this:

R1>

You can't write or add to a configuration in this mode, but you can run quite a few show commands. This is a good mode to have users in who need to see the configuration, but shouldn't be allowed to change it.

To get to the next level, type enable at the user exec prompt:

R1>enable

R1#

Notice that the prompt changed. This mode has two names, the official one being privileged exec mode. It's more commonly referred to as enable mode, since "enable" is what you type to get into this mode.

This mode gives you more options for show and other commands, but you still can't configure anything. To configure global commands, use "configure terminal", or "conf t", to enter global configuration mode.

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#

The prompt has changed again, and now global configuration commands such as hostname and no ip domain-lookup can be entered.

From here, you've got a lot of options, but we'll look at three you need to know for your CCNA exams. To apply configuration commands to an interface, enter interface configuration mode, as shown here:

R1(config)#interface serial0

R1(config-if)#

You must be in global config mode to get into interface config mode you cannot go from enable mode straight to interface configuration mode.

R1#interface serial0

^
% Invalid input detected at '^' marker.

Interface configuration mode allows you to apply an IP address to the interface, as well as many other commands related to frame relay, ISDN, and dynamic routing protocols.

For the CCNA, you need to know about two other configuration modes. To configure console commands (such as password protection), enter line configuration mode as shown here:

Four Important Commands For Your CCNA - CCNP Home Lab

More CCNA and CCNP candidates than ever before are putting together their own home practice labs. It's more affordable than it ever has been, and I receive emails daily from new CCNAs and CCNPs who say it's the best thing they could have done to improve their studies.

There are some commands you can configure on your lab routers that won't necessarily be on your CCNA or CCNP exams, but they will make life a lot easier for you. Let's take a look at just a few of these.

The command "no exec" is short, yet powerful. Occasionally you'll have what is referred to as a "rogue EXEC" process tie up a line, and you end up having to continually clear lines, which disrupts your practice. If you have an access server, I highly recommend you configure this command on your lines, as shown here:

ACCESS_SERVER(con)#line 1 8

ACCESS_SERVER(con)#no exec

From your CCNA studies, you know that the command "no ip domain-lookup" prevents a Cisco router from sending a broadcast to find a DNS server anytime you enter something that is not an IOS command - and that includes mistyped commands, which happens to all of us sooner or later. Make sure to run that command in global configuration mode on all your practice routers.

There are two commands I like to configure on the console line on all my practice routers and switches. The first is "exec-timeout 0 0", which prevents you from being kicked out of enable mode and back into user exec after a few minutes of inactivity. (This doesn't sound like much, but you'll get pretty tired of typing "enable" after a while.) The first zero refers to minutes, the second zero to seconds. Setting them both to zero disables the exec-timeout function.

The second command prevents the router from interrupting the command you're typing with a console message. If you've ever been in the middle of typing a router command and suddenly you're interrupted with a logging message, you know that can be pretty annoying. We don't want the router to not display the message, but we do want the router to wait until we're done entering data. The command to perform this is "logging synchronous".

R1(config)#line console 0

R1(config-line)#exec-timeout 0 0

R1(config-line)#logging synchronous

You won't see many of these commands on your exams, but after you configure them on your home lab devices, you'll wonder how you did without them!