1. Cisco 2 - Routers Perrine & modified by Brierley Page 18/18/2015 Chapter 5 IOS Internet Operating System (IOS)

2. Cisco 2 - Routers Perrine & modified by Brierley Page 28/18/2015 Chapter 5 IOS Internet Operating System What are its components How does it work

3. Cisco 2 - Routers Perrine & modified by Brierley Page 38/18/2015 Chapter 5 IOS Components Flash TFTP Rom RAM NVRAM Non Volatile RAM Random Access Memory Read Only Memory EPROM – Erasable Programmable Memory Trivial File Transfer Protocol Usually a hard disk

4. Cisco 2 - Routers Perrine & modified by Brierley Page 48/18/2015 Chapter 5 IOS Components Flash TFTP Rom RAM NVRAM Start Run

5. Cisco 2 - Routers Perrine & modified by Brierley Page 58/18/2015 Chapter 5 IOS Components Flash TFTP Rom RAM NVRAM Start Run Loads boot instruction set (bootstrap) to RAM on startup Back up server for configs and IOS IOS Configuration

6. Cisco 2 - Routers Perrine & modified by Brierley Page 68/18/2015 Chapter 5 Router Startup Sequence BootstrapROM loads bootstrap to RAM on start-up locate & load IOS Default sequence: flash TFTP Server ROM locate & load configuration file or enter ‘Setup’ mode NVRAM TFTP Server console

7. Cisco 2 - Routers Perrine & modified by Brierley Page 78/18/2015 Chapter 5 Locating IOS Software (Operating System) Use the configuration register that is saved in NVRAM to determine the sequence. (show version) provides the register address If NVRAM does not contain boot system commands that the router can use, the system by default will then go to flash memory. You can modify the sequence via the ‘configuration-register’ command: Router# configure terminal Router(config)# boot system flash IOS_filename Router(config)# boot system tftp IOS_filename tftp_address Router(config)# boot system rom [Ctrl-Z] Router# copy running-config startup-config

8. Cisco 2 - Routers Perrine & modified by Brierley Page 88/18/2015 Chapter 5 Configuration Register The configuration register is a 16-bit register located in NVRAM. The lowest four order bits of the register consists of the boot field.

9. Cisco 2 - Routers Perrine & modified by Brierley Page 98/18/2015 Chapter 5 Configuration Register There are 3 monitor modes: ROM monitor 0xnnn0 ROM 0xnnn1 from NVRAM 0xnnn2 TO 0xnnnF NOTE: When one enters the ROM monitor mode, use the b command at the ROM monitor prompt. For example to enter the ROM mode enter: Router(config)# config-register 0x2101

10. Cisco 2 - Routers Perrine & modified by Brierley Page 108/18/2015 Chapter 5 Configuration Register If the config-register is set to 0x2102 It tells the router to look in the startup configuration for boot system commands.

11. Cisco 2 - Routers Perrine & modified by Brierley Page 118/18/2015 Chapter 5 Trouble Shooting - IOS boot failures If a router doesn’t boot, then the following could be the problem : configuration file has missing incorrect boot system statement incorrect configuration register value corrupted flash image hardware failure Possible solutions: do a s run, and look for a boot system statement. If incorrect, go to global configuration mode and put a no in front of the statement. do a s version, and see if the configuration register is incorrectly set if the flash is corrupted, an error message during boot will appear none of the above, then it is possibly a hardware error. Call TAC.

12. Cisco 2 - Routers Perrine & modified by Brierley Page 128/18/2015 Chapter 5 Trouble Shooting - IOS boot failures Remember the configuration register is shown in show version (s ver). The configuration register is NOT displayed in show run or show start.

13. Cisco 2 - Routers Perrine & modified by Brierley Page 138/18/2015 Chapter 5 IOS File System Overview There are two types of software required for switches & routers to operate: 1.Operating system (IOS) 2.Configuration IOS image is in flash Running config is in RAM. Startup config is in NVRAM. Some of the functions specified by the config file are: IP addresses of the interfaces Routing protocols Networks to be advertised NOTE: To restore a previously good copy of the config file which is in NVRAM type: copy start run

14. Cisco 2 - Routers Perrine & modified by Brierley Page 148/18/2015 Chapter 5 IOS File System Overview Beginning with version 12 of the IOS, a single interface to all the file systems that a router uses is provided in the Cisco IOS File System (IFS). Some prefixes used: Bootflash: flash: ftp: nvram: rcp: Slot0: Slot1: system: Tftp:

15. Cisco 2 - Routers Perrine & modified by Brierley Page 158/18/2015 Chapter 5 IOS Naming Convention C2600-js-1_121-3.bin Hardware Platform (2600) Feature Set (enterprise w/ extended features) File format (relocatable; not compressed) Version number (12.13)

16. Cisco 2 - Routers Perrine & modified by Brierley Page 168/18/2015 Chapter 5 Backing up configuration files From the router to TFTP: copy running-config tftp at the prompt, enter the IP address of the TFTP server enter the name assigned to the config file or accept default name confirm each choice by typing yes each time From TFTP server to the router: copy tftp running-config at the prompt, select a host or network config file at the system prompt,enter the IP address of TFTP server where the configuration file is located at the system prompt, enter the name of the config file or accept the default name confirm the configuration filename & the server address that the system supplies

17. Cisco 2 - Routers Perrine & modified by Brierley Page 178/18/2015 Chapter 5 Backing up configuration files Another way to managing config files is to use the Transfer command of the HyperTerminal screen.

18. Cisco 2 - Routers Perrine & modified by Brierley Page 188/18/2015 Chapter 5 Upgrading/restore IOS files If you restore or upgrade the IOS file, backup the original file first!!!! Do: copy flash tftp router will prompt for the IP address of the TFTP server. router will prompt to erase flash if there is not sufficient room available a series of “e”s will appear to show the erase process. a series of “!”s will be displayed while the file is downloading. After the new flash successfully down loads it is then verified.

19. Cisco 2 - Routers Perrine & modified by Brierley Page 198/18/2015 Chapter 5 Upgrading/restore IOS files If the IOS image in flash has been erased or corrupted, you can restore the file while in ROM monitor mode. It is identified by: rommon 1 > As an example: rommon 1 > boot flash:c2600-is-mz.121-5 You can also us Xmodem from ROMmon: rommon 1 > Xmodem -c c2600-is-mz.122-10a.bin

20. Cisco 2 - Routers Perrine & modified by Brierley Page 208/18/2015 Chapter 5 IOS Components REVIEW Flash TFTP Rom RAM NVRAM Start Run Loads boot instruction set (bootstrap) to RAM on startup Back up server for configs and IOS IOS Configuration