Route switch operating system backup and upgrade

This article describes in detail how to back up and upgrade the Cisco router operating system. What operations do you need? The following articles will provide detailed answers.

Based on security considerations, network administrators need to back up the configuration information of network devices and IOS devices. If you need to deploy new features on network devices, in many cases, you need to upgrade the IOS version.

Accidentally deleting IOS by mistake or failing to upgrade IOS, it is common to enter the ROMMONROMMON status after restart, Which is abbreviated as rom monitor. This article introduces two methods for IOS backup and recovery.

Problem: It is difficult to try the operating system of network devices.

Many people who want to test CISCO certification often suffer from drills without equipment. A training center in Beijing opens an experimental environment for some VIP students free of charge based on their business development. In addition, many complex functions are configured and implemented on the topology composed of these devices. However, students often plug in the Console line, which causes great damage to the Console port. Based on the above considerations, the training center has established a remote lab on the basis of the original training lab. Most of the lab environments are isolated. That is to say, students have little access to real equipment.

The lab has also made some provisions, such as some dangerous command erase flash. However, some students do not comply with these Rules, resulting in IOS damage to some devices. Some devices are no longer available and can only enter the ROMMON status. Normal routing and forwarding functions and software configuration are not allowed. In this mode, most of the commands in the original IOS cannot be used.

When the network administrator fixes these devices, the Administrator first checks the configuration of config-register. The configuration of config-register should be 0x2102, it can be confirmed that IOS has suffered a fatal injury. In addition, the IOS features of some network devices have been upgraded. You also need to update these devices after obtaining new IOS devices. The network maintenance requirements of the Training Center are as follows:
* Upgrade the IOS version of some vswitches to support more features.
* Repair the damaged router IOS.
*
Tip:
In the experiment environment, IOS upgrades are also common. For example, if a CISCO 2950 switch is frequently suspended, the switch that is suspended does not have any warning information. After the switch is restarted, it returns to normal. By upgrading the IOS version of The vswitch from 12.11EA1 to the version later than 12.12 (EA2), the fault will disappear.

Router operating system backup solution
When you use config-register to check whether the register is correct, you need to check whether the IOS size and file name have been changed. Run dir flash: Command. Note that the flash is followed by the colon ":" in the command. After the command is executed, the existing IOS size and file name of flash are displayed, as shown below:
Rommon 1> dir flash:
File size Checksum File name
2179331 bytes (0x214103) 0x7b95 c1600-nsy-mz_112-15a_p

If the two items of File name and File size are inconsistent with the previous snapshots of the system, you need to restore the operating system. In this case, the administrator can recover the system based on the IOS backup and use the "TFTP" and "XMODEM" methods. The following describes the preparations before the upgrade and backup.

Select Transfer Protocol
There are three methods to upgrade or restore IOS: TFTP, XMODEM, and FTP. However, the first two methods are commonly used.
Upgrading the operating system of network devices in the lab is still relatively simple. Risks only exist in the lab network, but the risks of upgrading IOS in the production network are everywhere. Some unexpected things may occur during the upgrade of high-end devices. For example, if you use TFTP to transmit the Cisco 6509 switch to IOS, the problem may occur because TFTPTrivial File Transfer Protocol) the normal file transfer protocol supports transferring up to 32 MB of files, and the new IOS will exceed this limit, so you need to use FTP for upgrade.

1) TFTP
TFTPTrivial File Transfer Protocol, simple File Transfer Protocol) is a Protocol used in the TCP/IP Protocol set to transmit simple files between the client and the server, provides File Transfer services that are not complex and costly. TFTP is carried on UDP and provides unreliable data stream transmission services. It does not provide access authorization and authentication mechanisms, and uses the timeout retransmission method to ensure data arrival.
It can be seen from its name that it is suitable for transferring "simple" files. What is different from FTP is that it uses the UDP 69 interface, so it can traverse many firewalls. However, it also has disadvantages, such as unreliable transmission and no password verification. Even so, it is very suitable for transferring small files, such as IOS files on network devices.

2) XMODEM
The XMODEM protocol is the first communication protocol standard for two computers to transmit files through the RS232 asynchronous serial port. Compared with other file transfer protocols such as YMODEM and ZMODEM, The XMODEM protocol is easy to implement, suitable for scenarios with limited memory.
The XMODEM file sender splits the file into a fixed-length 128-byte data block. Each time a data block is sent, the next data block is sent after the other Party responds. The data verification adopts vertical accumulation and verification, you can also use 16-bit CRC verification. It is a simple ARQ automatic request re-transmission protocol, so it is also suitable for use in a 2-wire half-duplex RS485 network.