| A | B |
|---|
| Routers boot Cisco IOS software from | Flash memory; TFTP; ROM (limited) |
| most commonly the router looks to the boot system commands saved | in NVRAM |
| If Flash memory is empty | router can try its next TFTP alternative |
| Configuration register values | 0x---0; 0x---1; 0x---2 to 0x---F |
| 0x---0 | Use ROM monitor mode (manually boot using the "b" command) |
| 0x---1 | Automatically boot from ROM (default if no router has Flash) |
| 0x---2 to 0x---F | Examin NVRAM for boot boot system commands (0x---2 is the default if the router has FLASH) |
| Show Version | displays information about the Cisco IOS software version that is currently running on the router. As it continues to output, the show version command displays information about the type of platform on which the version of Cisco IOS software is currently running |
| Boot from Flash memory | You can load a system image from electrically erasable programmable read-only memory (EEPROM). The advantage is that information stored in Flash memory is not vulnerable to network failures that can occur when loading system images from TFTP servers. |
| Boot from network server | In case Flash memory becomes corrupted, you provide for a backup by specifying that a system image should be loaded from a TFTP server |
| Boot from ROM | If Flash memory is corrupted and the network server fails to load the image, booting from ROM is the final bootstrap option in software. However, the system image in ROM will likely be a subset of Cisco IOS software, that lacks the protocols, features, and configurations of full Cisco IOS software. Also, if you have updated the software since you purchased the router, it may be an older version of Cisco IOS software |
| Preparing for the use of TFTP | ยท 1) From the router, check to make sure that you can access the TFTP server over the TCP/IP network. The ping command is one method that can help you check this. 2) On the router, check to make sure that you can see and write into Flash memory. Verify that the router has sufficient room in Flash memory to accommodate the Cisco IOS software image. 3) On the UNIX TFTP server, check to make sure you know the file or file space for the Cisco IOS software image. For upload and download operations, you need to specify a path or filename |
| Use the show flash command | to verify that you have sufficient memory on your system for the Cisco IOS software that you want to load. |
| Cisco's IOS naming conventions | 1. 1) the platform on which the image runs; 2) a letter or series of letters identifies the special capabilities and feature sets supported in the image 3) specifics as to where the image runs and whether it has been zipped or compressed |
| copy flash tftp | [NOTE: Becareful when you use this - if nothing on TFTP and transpose will erase Flash) copy the system image to a TFTP server. The files can be renamed during transfer |
| copy tftp flash | After you have a backup copy of the current Cisco IOS software image, you can load a new image. You download the new image from the TFTP server by using the command |
| After you enter the copy tftp flash command, | the system prompts you for the IP address (or name) of the TFTP server. This can be another router serving ROM or Flash software images. The system then prompts you for the filename of the software image. |
