The Power-On Self Test (POST) is a process which occurs on almost every computer during bootup. This process is used to test the router hardware. When the router is powered on, software on the ROM chip performs tests on several hardware components, such as CPU, RAM and NVRAM. After the POST is completed, the router executes the bootstrap program.
After the POST has passed all the tests, the router copies the bootstrap program from ROM into RAM. After the program got into RAM, the CPU executes the instructions in the bootstrap. The main task of the bootstrap is to locate the Cisco IOS and load it into RAM. If you are connected with a console cable, at this point you will see text like the following on the console, depending on your platform:
System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fcl)
Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.
Generally, the IOS is stored in the flash memory, but it can be also stored in other places, such as a TFTP server. At the third step, the router loads the IOS image into RAM for execution by the CPU. If the IOS image can’t be located, a minimal version of the IOS is loaded from ROM into RAM. This version can be used to diagnose problems and load a complete version of IOS. When the IOS begins to load, you may see a string of pound signs (#), while the image decompresses.
Self decompressing the image :
###################################################################### [OK]
The last step in the router boot-up process is to locate and load the startup configuration file, also known as startup-config, in NVRAM. The startup-config contains configuration commands and parameters such as interface addresses, routing information, passwords and any other configurations saved by the network administrator. The router copies the startup-config from NVRAM into RAM as running-config. If a startup-config file is not found, the router prompts the user to enter setup mode. The setup mode is a series of questions prompting the user for basic configuration information. When the startup-config is not found, you will see a prompt like the following:
Would you like to enter the initial configuration dialog? [yes/no]
After the router is up and running, you can check the show version command to check some of the basic hardware and software components of your router.
Router>show version
Cisco Internetwork Operating System Software
IOS ™ C2600 Software (C2600-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by cisco Systems, Inc.
Compiled Wed 27-Apr-04 19:01 by miwang
Image text-base: 0x8000808C, data-base: 0x80A1FECC
ROM: System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE (fc1)
Copyright (c) 2000 by cisco Systems, Inc.
ROM: C2600 Software (C2600-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
System returned to ROM by reload
System image file is “flash:c2600-i-mz.122-28.bin”
cisco 2620 (MPC860) processor (revision 0x200) with 60416K/5120K bytes of memory
.
Processor board ID JAD05190MTZ (4292891495)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
32K bytes of non-volatile configuration memory.
63488K bytes of ATA CompactFlash (Read/Write)
Configuration register is 0x2102
As you can see, you will find here information like: IOS version, bootstrap version, location of the IOS image, CPU type, amount of memory, interfaces, amount of NVRAM, amount of flash memory, and the configuration register.
The configuration register has several uses, including password recovery. The default setting is 0x2102, which tells the router to load the Cisco IOS image from flash memory and the startup configuration file from NVRAM.
Understanding how a router boots up is important for your troubleshooting tasks. We hope you found this CCNA topic helpful and we will discuss more about IOS configuration and troubleshooting in other topics from our Cisco CCNA exam preparation series.
The last step in the router boot-up process is to locate and load the startup configuration file, also known as startup-config, in NVRAM. The startup-config contains configuration commands and parameters such as interface addresses, routing information, passwords and any other configurations saved by the network administrator. The router copies the startup-config from NVRAM into RAM as running-config. If a startup-config file is not found, the router prompts the user to enter setup mode. The setup mode is a series of questions prompting the user for basic configuration information. When the startup-config is not found, you will see a prompt like the following:
Would you like to enter the initial configuration dialog? [yes/no]
After the router is up and running, you can check the show version command to check some of the basic hardware and software components of your router.
Router>show version
Cisco Internetwork Operating System Software
IOS ™ C2600 Software (C2600-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by cisco Systems, Inc.
Compiled Wed 27-Apr-04 19:01 by miwang
Image text-base: 0x8000808C, data-base: 0x80A1FECC
ROM: System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE (fc1)
Copyright (c) 2000 by cisco Systems, Inc.
ROM: C2600 Software (C2600-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
System returned to ROM by reload
System image file is “flash:c2600-i-mz.122-28.bin”
cisco 2620 (MPC860) processor (revision 0x200) with 60416K/5120K bytes of memory
.
Processor board ID JAD05190MTZ (4292891495)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
32K bytes of non-volatile configuration memory.
63488K bytes of ATA CompactFlash (Read/Write)
Configuration register is 0x2102
Copyright (c) 2000 by cisco Systems, Inc.
ROM: C2600 Software (C2600-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)
System image file is “flash:c2600-i-mz.122-28.bin”
Processor board ID JAD05190MTZ (4292891495)
M860 processor: part number 0, mask 49
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
32K bytes of non-volatile configuration memory.
63488K bytes of ATA CompactFlash (Read/Write)
As you can see, you will find here information like: IOS version, bootstrap version, location of the IOS image, CPU type, amount of memory, interfaces, amount of NVRAM, amount of flash memory, and the configuration register.
The configuration register has several uses, including password recovery. The default setting is 0x2102, which tells the router to load the Cisco IOS image from flash memory and the startup configuration file from NVRAM.
Understanding how a router boots up is important for your troubleshooting tasks. We hope you found this CCNA topic helpful and we will discuss more about IOS configuration and troubleshooting in other topics from our Cisco CCNA exam preparation series.