Upgrade Cisco 851 IOS Step by Step

Instructions for upgrading IOS images on Cisco routers is already well documented and can easily be found on the Cisco website or general web search. This post is a review of the upgrade procedure as it relates to the 851 router.

Last week I received a new 851 router for a customers new office buildout. I skipped the web based initial setup procedure outlined in the setup guide and instead dropped in a template config through a console port session. Upgrading to the latest IOS image is part of my usual new router deployment routine. (See related entries section below for sample configs)

Prior to upgrading, have available or install and configure a tftp server. On my connecting pc, I have SolarWinds tftp server installed. From console or telnet session issue the "sh ver" command in privileged exec mode to view the current image:

Cisco851#sh ver
Cisco IOS Software, C850 Software (C850-ADVSECURITYK9-M), Version 12.4(15)T7, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2008 by Cisco Systems, Inc.
Compiled Thu 14-Aug-08 07:18 by prod_rel_team

ROM: System Bootstrap, Version 12.3(8r)YI4, RELEASE SOFTWARE

Cisco851 uptime is 48 minutes
System returned to ROM by power-on
System image file is "flash:c850-advsecurityk9-mz.124-15.T7.bin"

The current image file is c850-advsecurityk9-mz.124-15.T7.bin. The latest available image from CCO, as of this post is c850-advsecurityk9-mz.124-15.T9.bin

Download the latest image to your tftp root directory. (In order to download IOS images from CCO you'll need to be registered and associated with a SMARTnet or Comprehensive Maintenance service contract)

Next, issue the "sh flash" command to view the flash contents.

Cisco851#sh flash
20480K bytes of processor board System flash (Intel Strataflash)

Directory of flash:/

    2  -rwx    12701008   --- -- ---- --:--:-- -----  c850-advsecurityk9-mz.124-15.T7.bin
    3  -rwx        3179   Mar 1 2002 00:04:00 +00:00  sdmconfig-8xx.cfg
    4  -rwx      931840   Mar 1 2002 00:04:18 +00:00  es.tar
    5  -rwx     1505280   Mar 1 2002 00:04:41 +00:00  common.tar
    6  -rwx        1038   Mar 1 2002 00:04:55 +00:00  home.shtml
    7  -rwx      112640   Mar 1 2002 00:05:07 +00:00  home.tar

19353600 bytes total (4091904 bytes free)

Delete the existing image file. Issue the following command then enter and confirm.

Cisco851#del flash:c850-advsecurityk9-mz.124-15.T7.bin
Delete filename [c850-advsecurityk9-mz.124-15.T7.bin]?
Delete flash:c850-advsecurityk9-mz.124-15.T7.bin? [confirm]
Cisco851#

Just to be safe, startup your tftp server then backup the current config with the following command:

Cisco851#copy running-config tftp
Address or name of remote host []? 192.168.1.78 <-- enter tftp server ip
Destination filename [Cisco851-confg]?
!!!
7031 bytes copied in 0.060 secs (117183 bytes/sec)
Cisco851#

Issue the following command to transfer the new image to the router:

Cisco851#copy tftp flash:
Address or name of remote host []? 192.168.1.78  <-- enter tftp server ip
Source filename []? c850-advsecurityk9-mz.124-15.T9.bin
Destination filename [c850-advsecurityk9-mz.124-15.T9.bin]?
Accessing tftp://192.168.1.78/c850-advsecurityk9-mz.124-15.T9.bin...
Loading c850-advsecurityk9-mz.124-15.T9.bin from 192.168.1.78 (via BVI1):
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
[OK - 12747284 bytes]

12747284 bytes copied in 277.896 secs (45871 bytes/sec)
Cisco851#

Issue the reload command, confirm or save modified config if prompted. That's it. Any comments or questions welcomed.