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How to Upload Cisco IOS from ROMmon mode using xmodem via console cable

This document explains how to upload Cisco IOS® software onto Cisco Routers or Switches  from ROMmon mode using xmodem via Cisco console cable. This is used in disaster recovery situations where the Router Cisco IOS software is corrupted or crashed. I suggest you to use this procedure only where there are no Trivial File Transfer Protocol (TFTP) server software or RJ-45 network connections, and a direct PC connection to the router’s console port via console cable is the only viable option. Because this procedure depends on the console speed of the Router and the serial port of the PC, it can take a long time to download an image. The information in this document is based on Cisco IOS Software Release 12.1 and later. Xmodem command syntax on ROMmon Mode via Console cable xmodem [-c] [-y] [-e] [-f] [-r] [-x] [-s data-rate] In order to find out the syntax and […]

Difference between Xmodem, Ymodem and Zmodem

These three Xmodem, Ymodem and Zmodem are file transferring methods are the preferred methods. They have built-in error correction scheme and this means if there are any errors encountered while transferring a file, the computer will try to fix the error by having erroneous pieces of the file re-sent. These errors typically occur when there is some line noise, which could garble the characters, or in other instances. Xmodem Xmodem developed in 1977 by Ward Christensen and Xmodem is one of the most popular file-transfer protocols. Although Xmodem is a relatively simple protocol, it is fairly effective at detecting errors. It works by sending blocks of data together with a checksum and then waiting for acknowledgment of the block’s receipt. The waiting slows down the rate of data transmission considerably, but it ensures accurate transmission. Xmodem can be implemented either in software or in hardware. Many modems, and almost all […]