Hi and welcome to this CertificationKits CCNA training video in dealing with basic router configuration. We are going to be talking about the basic CCNA level router configuration, configuring hostnames, the configuration of IP addresses, banners, and interface descriptions and just verification of all these configurations with some show commands.
I brought up the router prompt and what we are going to do is go in and get in global mode and take a look at configuring the hostname and the router. So the first command I put in here is enable to get me into privilege mode. Now let’s say I forgot what mode I need to be in or I want to see what the router command is to configure the hostname in the first place. What I can do is I can do the show run and which is short for show running-config and I can go in and take a look. Right now the hostname of the router is router and what’s nice about the show run is I can actually see the command in the show run that I use to change the name of the router. Hostname, space router, router being the router’s name, hostname being the command to enter the router’s name. Now the running-configuration is how the router is currently configured. There is also a startup-configuration which is a saved configuration which has stored a non-volatile memory. So if the router were to be shut down, the startup-configuration would be loaded to configure the router. The running-configuration and the startup-configuration do not have to match so if I make a change that I don’t like, I could load the startup-configuration and overwrite the running-configuration and any changes that I’ve made that the router would be gone which is nice if you are troubleshooting.
Maybe you are going to somebody’s business and you make a mistake, things don’t work out the way you planned it, you can just go ahead and overwrite all mistakes you made. In worst case scenario if you can fix the device, you can get it back to the state it was in before you got there. So again I’m looking at the running-configuration. I want to go in and change the name of the device. So what I’ll do is I will get out of the show run, I hit any letter on the keyboard to get me out and then I’m going to go in the global mode. Every command you see in the running-configuration, at last you need to be in global mode to enter it. Some commands you need to go to a further mode so hostname router is a global mode command so I get in the global mode by typing in configure terminal. Now all I have to do is look at the exact command that I put up here, well that’s already in the running-configuration which is hostname and then I give the router the name and I’ll call this router “Router 1”. By typing in router1 or hostname router1, go in and I’ve actually changed the name of the router. Now, that name change that I’ve done will be lost if I reboot the router, this is in RAM, RAM is Random Access Memory and it’s volatile. Meaning if I shut the router off, it loses power, I lose the change. So I don’t want to shut the router off until I’ve saved it. To verify that, I can do show startup-config and then getting this nonvolatile configuration memory is not present. I thought I was getting an error there for a second but it’s not an error, it’s just telling me that nonvolatile configuration memory is not present. What that means is there isn’t a saved configuration on the router. So if I were to shut down, the router would come up with all default configurations. If I want to save this, so if I do shut down the router, this configuration change I’ve just made will be saved. I type copy, running-config, startup-config. Running-config being the source configuration file, startup-config meaning the destination and I hit enter and I’ve saved the configuration.
Now, if I want to view what is an NVRAM, so if the router is restarted inadvertently I could go in and I can check it out, and here it is, here is my command in the startup-configuration, so that’s the name of the router. If we were to shut down, that router name will be saved. Now that’s how I configure the hostname. Let’s go in and take a look at configuring in an IP address. I’m going to go in and do a show run just to take a look at the current configuration of the interfaces and see what IP addresses are on there automatically. Since this router has a minimal configuration changes from the default, each interface should not have any IP address on there. I’ve got two interfaces. Interface serial0 which is from my LAN connection and interface Ethernet0 which is from my LAN connection. Notice it says “No IP address on each interface” or under each interface. So what I want to do is, if I want to go in and actually change the IP address or set an IP address on each interface, I’m going to have to follow the steps that I actually see right in front of me with the show run and I’ll start in global mode to do that, I’ll follow the steps and I’ll go in and add an IP address to the interface.
Let’s take a look. Configure terminal or config tfor short. It gets me into global mode. Now I notice that it says “No IP address underneath interface serial0.” So what that tells me is if I want to set an IP address on interface serial0, I have to type interface serial0 first to enter the interface mode and then I can go ahead and set the IP address. INT for short, tab it out so I can see what I’m typing in, interface S0, “S” is for serial, and it’s taking me the serial0 interface. I know I’m in interface mode because if we could go in and take a look right here, it has the router name, space or no space but parenthesis, config dash if, end of parenthesis and then have the pound sign. The config dash if, tells me I’m in interface mode. Let’s say I forgot the command to set the IP address. All I have to do is look up here and it says “No IP address” so the opposite of no IP address would be IP address so I can go in and type ID address but if I just hit enter, IP address it says “Incomplete command” so I’m going to bring up my previous command with the up arrow, space, put a question mark, oh yeah I’m entering the IP address so I can go in and it shows me what that help command, what I’m entering or what I can’t enter or what command component is expected next.
Now take a look right here, IP address is what’s expected next and A.B.C.D stands for dotted decimal notation so it’s expecting an IP address in dotted decimal notation. So I’m going to go in and put an IP address in there, 102168.1.1 with the default subnet mask for a class C network and I hit enter. I didn’t get an error. Now remember what the router prompts if I do everything right, it’s not going to give me an error but it’s also not going to tell me I did anything right, it’s just not going to give me an error. So let’s go in and set an IP address on the other interface as well as view this IP address we’ve just set. Control-z takes me back to privilege mode show running-config will show me any changes I’ve made. I always do and show running-config after making some changes to the router just to verify that they are there. Hostname router1 I said earlier, interface serial0, IP address 192.168.1.1 255. 255. 255.0 exactly what I typed in. I’ve got one more interface to go and again I can use what’s in front of me in the show run to help guide me into setting that IP address on interface Ethernet0. All configuration starts from global mode, I type interface serial0, oh I’m sorry interface Ethernet0, E for Ethernet, I don’t have to type the whole thing out but when you are just starting out with the router prompt it’s a good idea to type the whole command or at least put the first few letters and then hit tab and make sure it completes it for you. That way you get some familiarity with the complete commands. Ethernet0 on the CCNA exam by the way, they do take shortcuts in the CCNA simulators. I hit enter just like this and I take a look. No IP address, again the opposite of that would be IP address and I go in and put an IP address.
Watch what happens if I put an IP address 192.168.1.2, same subnet mask. If the interface was up, I didn’t get any errors right here and I didn’t get any errors because my interfaces are down. If my interface was up, what would happen is my router would look at my Ethernet0 interface and look at this IP address 192.168.1.2 and the class C subnet mask and notice that this serial interface has an IP address that is in the same subnet or network. In this case it’s a network address so the serial0 interface is in the same network, that’ not going to work for the router. The router is not going to like it when you put IP addresses on different interfaces that are a part of the same network address or a part of the subnet address. The reason it doesn’t like that is because every different broadcast domain on the router needs its own subnet or network address, that’s how the router routes.
Having multiple broadcast domains with the same subnet or network address is very similar to a couple of different cities in California using the same zip code. If multiple cities had the same zip code, the post office wouldn’t know the best way or which was the appropriate office to forward the mail to. So what I’m going to do is I’m going to use my up… to bring up the previous command and change the network address here to that two network, in that way the router can function appropriately and I’ll put it .1 for the gateway and that way the router can function appropriately when I enable the interfaces. Here I’ve used control-z to get out of the interface back to privilege mode. I’m going in and I’m verifying the IP addresses that I’ve just set. So again I see the hostname I’ve set earlier, interface serial0 with the IP address 192.16811. I go enter one line at a time. I can see the IP address on Ethernet0 which is 192.168.2.1 just like I typed it in. I’ve exited out of the router and the reason I exited out is I want to show you the point; our starting point from the router. Now the starting point is going to look very similar whether we tell that in using the auxiliary port to connect to the router or the line console. Now what you can do is you can put a little message here for people to see when they are connecting up to the router and it’s basically a descriptor you can use for the router. The message is called the banner message of the day to give people who are connecting to the router some information about it. Very helpful for remote situation or remoting into a router. You don’t physically see the router in front of you, large organizations with multiple routers, it’s a nice idea to put that there. That way if somebody does connect up or they are… in, they know that they are… into the right device. Let’s put a description on router1 so when people connects up to it, they know what router they are connecting to.
I start off in user mode, get into privilege mode, type config t which takes me into global mode. Global mode is the mode where I’m going to specify this banner message of the day and all I type is banner, MOTD. MOTD is standing for Message of the Day and I’ll put a question mark if I don’t know what to do next. What it wants is it wants a character called the delimiting character and what that is, that character marks the beginning and the end of the router message. Now when you are creating the banner message of the day, you want to use a character for the delimiting character that something is not going to be using when you are typing your message so I’ll put a pound sign. What I like to do is I like to hit enter after I put the delimiting character because what it allows me to do is it allows me to enter my message in paragraph format. This is router1. And I put… this is router1, please to do not make any changes. When I’m done, I’ll put a space in there, put the delimiting character again, I hit enter and notice I did not get any errors. If I don’t get any errors that’s a good thing again it’s not going to pat me on the back when I do something right which is not going to reprimand me for doing something wrong. Control-z and again like always, I will do show running-configuration and check out my banner message of the day and here it is. The banner message of the day, this represents the delimiting character which is the pound sign that I used and it shows my message. If I want to see my message in action, what I need to do is exit out of the router and watch what happens when I hit return before I get to user mode. I get the message, so this is router1, please do not make any changes. And again this can be very helpful when the need for identifying routers in a larger routed environment, when there is a lot of routers is important, so banner messages are helpful for identifying routers.
Let’s take a look at a couple of other descriptions that we can put on interfaces. These are little message we can put on the interface to tell people where a particular interface is connected. So let’s go in and when we do this you go to remember it might not be a big deal to put a description on an interface when there are only two interfaces on the router. When you got routers with hundreds of interfaces out there and you’ve got 30 routers in a network, it’s a pretty good idea. So to put a description on an interface, we need to get to interface mode and type enable to get into privilege mode, config t for a configured terminal to get in the global mode and from here is where I can go to the interface. I type interface, S for serial0 and now I’m in interface serial0’s configuration. Again I know I’m at interface mode because it says config-if. The description command, I’ll have to type out this des and I can hit tab to complete it, it’s a little bit different. I don’t have to specify a delimiting character all I do is type description and type something that describes where the link goes.
In this situation I’m just going to put this is the LAN connection and hit enter. Just like everything else, control-z gets me back to privilege mode, I’m going to go in and check my work. Show run and right here underneath interface serial0, I can see the description. This can be helpful when people are remoting in, don’t know where it’s connecting to or like I said some routers with multiple interfaces need descriptions just so you can remember which one goes where. Looking at Ethernet0, I notice there is no description on E0 interface so I’m going to go back in and put a description on Ethernet0. Ethernet0 in small networks typically would be the gateway so I’m just going to put a little description here, I’m going to put this is the LAN gateway, LAN being Local Area Network is I need to say that so I hit enter. Control-z, show my work, do a show run and I can see interface Ethernet0 description, this is the LAN gateway and again we’re just giving people information about the router so if somebody knew where to come in or your memory is short, you forget what interface goes where you can put a little description on there as a reminder.
We’ve gone ahead and exited out of the router and we’ve configured the banner message of the day. We have configured the router name which is router1. If I get into privilege mode and I do a show running-config, I can see that we’ve also set descriptions and IP addresses on the interfaces. Now I want to point out that we are not always going to be configuring a router from a scratch. There may be configuration on the router already and we have to change that configuration. Let’s take a look at just changing the hostname of the router. So if I want to change the hostname of the router, I do it much in the same way that I set the hostname in the first place with the hostname command. I go into global mode and I just type hostname correctly, router and I’ll put router “A” this time. Notice, I did not have to remove the old variable which would be the command no hostname router1, all I have to do is type in hostname and the new variable which is router “A” and it configures it automatically for me. I don’t have to get rid of anything. If I do want to get rid of it, no hostname router “A” and go back to the default factory configuration which would just be router as the hostname and all I have to do is put a no in front of that command and it will go ahead and get rid of it for me. Now if I do a control-z in a show running-config, I can see that I’ve gotten rid of the hostname on the router and anything else in here that I want to get rid of. I can do it the same way.
If you want to get rid of the description on an interface serial0 or I want to change the description I’ll just go “No description” this is LAN connection, I will get rid of it. If I want to change it I just type description and the new variable or the new description. I want to get rid of the IP address, it’s no IP address so everything in here that I see if I want to get rid of it. All I have to do is put a no in front of it as long as I’m in the right mode. If you notice right here, the simple command shut down turns off the interface. It doesn’t allow connectivity. So if type no shut down underneath interface serial0, I will go ahead and turn that interface on. Now there is one more show command I want to go over before we conclude this CCNA lesson. If you will notice I really like running-configuration, the show running-configuration command because everything that I type in that changes the configuration on the router shows up when I type show running-configuration but if I want to get more detailed information or status-oriented information by the particular interface, there are some other commands I can check out like show interfaces. Show interfaces shows me status information about the interface, shows me the description I put in there, I can go in and check that out, it shows me my IP address, bandwidth, maximum transmission unit and buffer information as well as traffic information about a particular interface.
I can do show interfaces serial0 to see just serial0 or show interfaces will show me all the interfaces on the router. Another command is show IP interface which will show me just IP specific information about an interface that’s why it’s show IP interface for the IP protocol. Here I can check out my IP address, status of the interface and IP specific information. ICMP, a popular example of that is the ping. So I can go in and check information… Now I’d go in and do the show IP interface brief command and I get… I’m using short cuts here, show IP interface brief and it gives me brief information about my interfaces namely the interface; IP address and up or down and right now it says administratively down, meaning the shut down command is still active on that interface. Now again to reiterate, I really like to show running-configuration command for a quick look in how the router is configured. Show interface is good to get some information about the router. Show IP interface is also good but as far as just checking out what I’ve gone and then configured.
To see the configuration of the router itself, show running-configuration is a good one and if I want to save that configuration, I can use a copy command; copy, running-configuration to start up configuration. So it’s copy source destination, I take what’s in RAM, put it in an NVRAM. That way if somebody trips over the power plug on the router or it inadvertently gets shut down, power outage and I’ve seen people losing configuration information because they didn’t save it because of the power outage, I can go in and save it. Now if the power does go off, the router reboots, start configuration will get loaded and will be configured exactly the way I have it right now. So we have talked about the basic CCNA level router configuration, setting the hostname on the router, specifying IP addresses on interfaces, setting some banners to identify the router, the descriptions that actually identify the interface and verification of our configuration with the great show running-config command as well as a couple of show interfaces and show IP interface commands. I hope you have enjoyed this CertificationKits CCNA training video dealing with the basic configuration of your router.