Downgrade Software on Router That Runs Cisco IOS-XE SD-WAN to Classic Cisco IOS-XE Software

By | September 9, 2022
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Problem

The user cannot configure boot system flash bootflash: image settings in order to boot the original Cisco IOS-XE image:

router#config-transaction 

admin connected from 127.0.0.1 using console on router
router(config)# boot ?
                   ^
% Invalid input detected at '^' marker.
router(config)# boot system flash bootflash:c1100-universalk9_ias.16.06.05.SPA.bin
-------------------^
syntax error: unknown command

Solution

The procedure is similar to a software upgrade to Cisco IOS-XE SD-WAN software.

  1. Copy the required software to the bootflash or upload to a USB flash drive.
  2. Ensure that the router is connected to a management console.
  3. If PnP is running, stop PnP in order to allow access to the CLI:
    router# pnpa service discovery stop
  4. Change the config-register to 0x0:
    router# config-transaction
    router(config)# config-register 0x0
    router(config)# commit
    router(config)# end
  5. Verify that the config-register is set to 0x0 when the router reboots:
    router# show bootvar BOOT variable = bootflash:packages.conf,1;bootflash:prev_packages.conf,1; CONFIG_FILE variable does not exist BOOTLDR variable does not exist Configuration register is 0x0 Standby not ready to show bootvar
  6. Reboot the router:
    router# reload
    Proceed with reload? [confirm] Yes
    The router reboots and goes into ROMMON mode.
  7. Check the router’s bootflash in order to obtain the software image name to load:
    rommon 1> dir bootflash:
    rommon 2> boot bootflash:c1100-universalk9_ias.16.06.05.SPA.bin
    The router reboots with the previous software image.
  8. Set config-register to the original value (for example, 0x2102) after the reload and save it:
    router# config terminal
    router(config)# config-register 0x2102
    router(config)# boot system bootflash:xxxx.bin
    router# copy run start

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