Cisco practices-IOS software Backup Recovery

This article mainly introduces the backup and recovery of IOS software. An important method is the backup and recovery of IOS software. Today, I will share with you some tips on the backup and recovery of this IOS software. We hope to make progress together with readers.

I. a principled suggestion

Before upgrading the IOS software of a Cisco router or vswitch, copy the software from the original Cisco flash memory to a network device such as a TFTP server for backup. To prevent the new impression files from being broken or burned out and not running properly.

This principled suggestion is very important. Because the IOS impression file is like a flower in the greenhouse, it will strike after a slight carelessness. For example, when the new IOS software impression on TFTP is copied to the flash memory of the router during the IOS software upgrade process, if the flash memory is insufficient, the original IOS impression will be overwritten. In this case, if there is a problem with the new version of IOS software, the previous IOS software cannot be restored because it has been replaced by the new version. This will cause a router startup fault. If you have backed up the old version of IOS software in advance, you only need to perform a simple restoration job when this problem occurs.

Ii. Prepare for IOS software backup and recovery

Before backing up or recovering the IOS software, our network administrator must make some preparations to ensure smooth operation. Generally, the network administrator needs to verify four tasks.

First, ensure the normality of connecting vrouters and other network devices to the network server. If the vro cannot smoothly access similar network servers, such as TFTP, the backup or restoration cannot be completed. This is because ordinary PCs, such as routers, are different after all. There is not enough space on the router and other network devices to save the backup file of the router IOS software. That is to say, to back up the IOS software of the router, remote backup is required. This requires that vrouters and other network devices can smoothly access servers on the enterprise network.

Second, ensure that the network server has enough space to store IOS software backups. Although IOS software is generally not as large as Windows operating software. Generally, IOS software backups do not exceed 100 MB. However, for the sake of security, before backing up the IOS software, the network administrator needs to check whether there is enough space on the network server that saves the backup file.

Third, verify the IOS file name and path to be backed up. Generally, IOS software for Cisco switches and other network devices is stored in flash memory. However, in some special cases, the router can run IOS software from a remote TFTP server. Therefore, before backing up or upgrading the IOS software, the network administrator needs to check which IOS software is running on the router to be backed up or upgraded.

Fourth, if you restore the IOS software, you need to verify that the IOS software to be used is saved in the default path of the TFTP server. This task is very important. Generally, when the TFTP server restores the IOS software to the flash memory of the router, it copies the IOS software in the default path of the TFTP server to the flash memory of the router. If no IOS software is available on the TFTP server, the restoration job will fail.

Only when the above four jobs are correctly verified can the next job be performed.

Iii. Verify flash memory

As I have mentioned, Cisco routers and other network devices use IOS software in flash memory in most cases. This is also the recommended configuration for Cisco. Therefore, whether you are backing up IOS software or restoring or upgrading IOS software, you must first verify the relevant content in flash memory.

For example, when the IOS software in flash memory is restored or upgraded, You need to verify that flash memory has enough space to save New impression files. Because the space required for different versions of IOS software is different, this verification becomes very important when the IOS software is upgraded.

To verify that there is sufficient available space in flash memory, the network administrator can use the show flash command. This command displays the number of memory used by the current IOS software for network devices such as routers. At the same time, it will show whether there is enough space to accommodate the current impression file and the new impression file. As I mentioned earlier, if there is not enough space to accommodate the existing and new image files that the network administrator wants to use at the same time, the original image files will be deleted. This is very dangerous.

In addition, in some vro versions, you can use the show version command to display the number of Flash files more accurately. However, the network administrator must be clear that these two commands are still different. The former command will display the names of all files in flash memory. The latter command only displays the file names used by network devices such as the current vro. If the router has a large flash memory, it also has multiple versions of IOS software. The Network Administrator only needs to back up the IOS software currently used by the router, and can use the latter command to confirm the IOS software currently used by the router. However, generally, only the IOS software version is saved in the flash memory of the router. This is mainly because the flash memory space is usually not large.

Iv. backup and recovery of common IOS software configurations

In practice, I prefer to back up and restore the IOS software through the console on my laptop. For example, when I back up and restore the IOS software, I like to use the laptop's Ethernet port to connect directly to the router's Ethernet port, and then back up the IOS software to the TFTP server through the console.

To use this configuration, the following conditions must be met.

First, the Administrator's workstation must have the TFTP server software installed. That is to say, up to now, TFTP servers must be used to back up and restore network devices such as Cisco routers. There are no other methods.

Second, the connection between the router and the notebook must use a crossover cable. That is to say, the dual-host couplet network cable is used. In this regard, many Cisco network equipment management personnel who are just getting started will often ignore this, resulting in failure to connect to the router normally.

Third, the IP address of the laptop must be the same as the IP address of the router interface. By double-clicking the direct connection to access the vro, their IP addresses must be in the same subnet. Otherwise, even if the vro has the function of connecting different subnets, The Notebook cannot be smoothly connected to the vro.

Fourth, if the IOS software is copied from the router flash memory to the notebook, the network administrator also needs to provide the correct IP address of the TFTP server. In practice, the network administrator can use the Ping command to test whether the IP address entered by the network administrator is valid. By default, the destination file name of the backup is the current source file name. We do not recommend that you make changes if you do not have special requirements.

5. Additional reminders for IOS software upgrade or job recovery

Although IOS software upgrades are similar to backup jobs. However, because the recovery of the IOS software is directly related to the operation of the router, I still need to say a few words about the upgrade of the IOS software.

Reminder 1: If the network administrator copies the backup file on the TFTP server to the flash memory of the vro, if the two files have the same name, the network administrator will be asked whether to overwrite the previous IOS file, that is, the IOS file in the router flash memory. Therefore, it is very important not to change the name of the backup software during software backup. As a reminder, you can tell the network administrator whether to back up or upgrade the existing IOS software.

Reminder 2: After the IOS software is restored, it takes effect only after it is restarted. That is to say, after the network administrator copies the backup file to the flash memory, if the file is damaged due to overwriting, the router will not immediately remind the network administrator. Only the vro can be found the next time it is started. Therefore, the network administrator must be careful when using the software recovery function. Because vrouters lack relevant self-detection functions. If the update fails, the network administrator only restores the IOS software through ROM monitoring. This is not a good solution. The network administrator should try to avoid this situation. In addition, if a new IOS file is being loaded and there is not enough space in flash memory to store the new and existing files at the same time, the router will ask whether to delete the existing content in the flash memory before writing the new file to the flash memory. Before selecting this option, make sure that the existing files have been backed up and will not affect the subsequent operation of the router. After all, whether during the upgrade or backup process, the primary task is to ensure the normal operation of network devices such as routers.

Reminder 3: If you need to recover the IOS software in the flash memory of the router, the network administrator must ensure that the IOS file to be copied to the flash memory is on the default TFTP server of the server. Unlike backup, the TFTP server does not ask the specific location of the original file during restoration, but directly reads the file from the default location on the TFTP server. If you do not place the recovered files in the default TFTP server directory, the restoration or upgrade process will fail.

The above is the summary of my work in recent years. We hope these suggestions can help you better manage the backup and recovery operations of Cisco network devices. Finally, the author repeatedly stressed that it is difficult to guarantee a one-time success for software restoration or upgrade. Therefore, before performing these jobs, the network administrator must ensure the security of the original IOS software. Do not be too confident about yourself. When you do not back up the original IOS software, you can immediately restore and upgrade the software.