Bringing up a Cisco Router

When you first bring up a Cisco router, it will run a power-on self-test (POST). If it passes, it will then look for and load the Cisco IOS from flash memory-if an IOS file is present. (Just in case you don’t know, flash memory is an electronically erasable programmable read-only memory- an EEPROM.) After that, the IOS loads and looks for a valid configuration-the startup-config- that’s stored by default in nonvolatile RAM, or NVRAM.

The next that router outputs is boot process. It’s information about the bootstrap program that first runs the POST, and then tells the router how to load, which by default is to find the IOS in flash memory. After the IOS is decompressed into RAM, the IOS is then loaded and starts running the router, as shown below (notice that the IOS version is stated as version 12.3[22]):

Cisco Internetwork Operating System Software
IOS (tm) 3700 Software (C3745-ADVIPSERVICESK9-M), Version 12.3(22), RELEASE SOFTWARE (fc2)
Technical Support:
Copyright (c) 1986-2007 by cisco Systems, Inc.
Compiled Wed 24-Jan-07 18:55 by ccai
Image text-base: 0x60008AF4, data-base: 0x61F60000

Once the IOS is loaded, the information learned from the POST will be displayed next, as shown here:

cisco 3745 (R7000) processor (revision 2.0) with 121856K/9216K bytes of memory.
Processor board ID XXXXXXXXXXX
R7000 CPU at 100MHz, Implementation 39, Rev 2.1, 256KB L2, 512KB L3 Cache
Bridging software.
X.25 software, Version 3.0.0.
2 FastEthernet/IEEE 802.3 interface(s)
DRAM configuration is 64 bits wide with parity enabled.
151K bytes of non-volatile configuration memory.
16384K bytes of ATA System CompactFlash (Read/Write)

Once the IOS is loaded, and up and running, a valid configuration will be loaded from NVRAM. If there isn’t a configuration in NVRAM, the router will go into setup mode – a step-by-step process to help you configure the router. You can also enter setup mode at any time from the command line by typing the command setup from something called privileged mode, which we’ll get to in a minute.

Setup Mode

You have two options when using setup mode: Basic Management and Extended Setup. Basic Management only gives you enough configurations to allow connectivity to the router, but Extended Setup gives you the power to configure some global parameters as well as interface configuration parameters. To enter setup mode, just say “yes” or “y” to the following question:

--- System Configuration Dialog --- 

Would you like to enter the initial configuration dialog? [yes/no]: y

Basic Management setup configures only enough connectivity for management of the system. But since you can do so much more with Extended Setup, this mode will ask you to configure each interface on the system, as seen here:

Would you like to enter basic management setup? [yes/no]: n 

First, would you like to see the current interface summary? [yes]:

Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES unset administratively down down
FastEthernet0/1 unassigned YES unset administratively down down

Configuring global parameters:

Enter host name [Router]:

I’ll stop here with this type of setup mode configurtion, because until now I didn’t saw someone to use it ;-)

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