Cisco. First edition. We connect two networks.

Let's start.

How does a Cisco router start? Right from the console cable.
This is the light blue wire with RS-232 and RJ-45 connectors that came with the equipment. It needs to be connected to the computer to a free COM port. Now you can do anything with your hardware. Unless, of course, you have set a password for console connections (we'll talk about how to overcome someone else's password on your hardware later).
')
So, open the terminal connection client software, for example, PuTTY. In the program, specify the connection port (COM1) and the connection speed (9600).
What we see? Black screen, blinking cursor and nothing else? It means, most likely, the connection speed on the router is different. As a rule, it can be a speed of 115200. If it does not fit (and this is rare), then you will have to pick it up. In any case, it is still worth checking which COM port is indicated to which connection is made.

Great, sorted out! Everything is normal and we see an invitation from the router. By default, it will look like this: Router>
This means that we are in user mode. From this mode, very few commands are available. All these commands only allow you to monitor the operation of the router, but do not provide an opportunity to make changes to the configuration. From this mode you can execute, for example, the command Ping or show ip interface .

In order to change the working configuration (read, configure) of the router, you must enter the privileged mode. Privileged mode can be password protected. In order to enter the privileged mode, type the command enable . After that, the command line prompt will change to Router #

Many more teams are already available here. In this mode, you can make changes to the working configuration and save the modified configuration in the ROM.

But the basic configuration of the router is carried out from the global configuration mode. It can be accessed from privileged mode by running the configure terminal command. The prompt will change to Router (config) # . As you have already noticed, the command line prompt indicates which mode you are in.

Get to the point.

To begin with, let's do the simplest - connect two networks using our router.
The Internal network has an address range of 192.168.10.1/24 , the router's address in it is 192.168.10.254 , the network adapter is FastEthernet0/0
The External network has an address range of 10.54.0.0/16 , the router's address in it is 10.54.0.1 , and the network adapter is FastEthernet0 / 1 .
In global configuration mode, enter the Interface FastEthernet0 / 0 command. The invitation will be: Router (config-if) # . The default interface has no address and is even turned off. First enter the IP address. This is done by the following command: ip address 192.168.10.254 255.255.255.0 .
Remember that interface is off? It is turned on with the no shutdown command . If all is well, then run through the inscription:

Router(config-if)#no shutdown

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up

The first line says that everything is fine with the network interface in terms of the physical and data link layer (the network cable is connected and compatible equipment is working at the other end). The second line says that the Network Layer (IP Layer) also works as it should.

Next you need to exit the FastEthernet0 / 0 interface configuration mode, enter the FastEthernet0 / 1 interface and configure its IP parameters.
With this, you can do it yourself.

You can check whether everything is configured correctly by returning to the privileged mode ( exit command ) and issuing the show ip interface brief command. It will show information about the status of network interfaces. The output of the command will be something like this:

Router#show ip interface brief
Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 192.168.10.254 YES manual up up

FastEthernet0/1 10.54.0.1 YES manual up up

Hooray!

Done! A router can transfer packets from one network to another and vice versa.
Almost done =) All changes and settings that we have made now are saved only in the RAM of the router. To save the configuration after rebooting, it must be copied to the ROM. This is done easy. From the privileged mode, the copy running-config startup-config command is entered. Now reboot is not scary!

Yes, one more small detail. If you turn on a router that does not have a configuration, then IOS will suggest using the wizard to configure the basic parameters of the router operation. Politely refuse him. Why just when it can be difficult? =)

Total:

To work, we need 4 basic configuration modes:

Custom mode: Router>
Privileged mode: Router #
Global configuration mode: Router (config) #
Object configuration mode (interface, routing protocol, etc.): Router (config-if) #

That's all. Agree, you thought it would be more difficult!

In the next issue, I plan to write about using the Packet Tracer 5.0 simulator and the GNS3 emulator. I will try to prepare a video about how these necessary and useful programs work. Issues I plan to cook once a week.