Stuck in ROMMON: Cisco ISR 4000 series router

 Today I am going to talk about the issue which is sometimes you get in the Cisco 4300 or Cisco 4400 ISR routers. It is one of the basic article for network engineers where if the ISR router is struck in the ROMMON mode then how to recover that ISR router back with the IOS image.

Cisco 4400 and Cisco 4300 series routers have IOS-XE images looks very similar hence in case you configured Cisco 4400 with IOS-XE release for Cisco 4300 or vice-versa, router will not boot-up completely, instead will get stuck in ROMMON.
Fig 1.1- Cisco ISR 4451-X

Here you have Cisco 4400 configured with an IOS-XE release of Cisco 4400

Let me now talk about the step by step configuration which will help you guys to come out of the ROMMON mode as below 

Break router into ROMMON mode using break sequence during boot-up
rommon 1 >

Change the config-register value to 0x0 to ignore the boot variable configured in startup config
rommon 1 > confreg 0x0

You must reset or power cycle for new config to take effect
rommon 2 > reset

This will bring router into ROMMON mode once again. Now change the config-register value to 0x2102
rommon 3 > confreg 0x2102

Now we need to configure correct boot variable from ROMMON
rommon 4 > boot bootflash:isr4400-universalk9.03.15.01.S.155-2.S1-std.SPA.bin

Once router is up and running, you can delete the incorrect boot variable and configure the correct IOS-XE release

Save the changes
NDNA#write memory