Cisco Rommon – IOS downloading

If for some reason your Cisco IOS doesn’t boot properly then Cisco device stays into ROMMON (a mini operating system that boot the actual IOS).

ROMMON offers CLI which you can use to download the proper IOS from TFTP server – this post shows the example of this operation. In this post I assume your TFTP server is already configured (you can read my post about TFTP server here)

ROMMON session:

//
// init tftp, ether port, flash
//
ap: tftp_init
ap: ether_init
ap: flash_init

//
// setup your IP settings
//
ap: set IP_ADDR 192.168.0.105
ap: set NETMASK 255.255.255.0
ap: set DEFAULT_ROUTER 192.168.0.1


// I found that a different ROMMON can use another set of IP variables.
// If you are not sure - you can use both configurations in the same time
ap: set IP_ADDRESS=192.168.0.105
ap: set IP_SUBNET_MASK=255.255.255.0
ap: set DEFAULT_GATEWAY=192.168.0.1


// download the IOS from your TFTP server
ap: tar -xtract tftp://192.168.0.103/c1200-k9w7-mx.123-8.JED.tar flash:


// If the command above failed then you can check if your AP has at leases IP (Layer 3) connection with TFTP server
ap: arp
     255.255.255.255  ff:ff:ff:ff:ff:ff  0  6
       192.168.0.103  24:0a:64:56:37:01  0  35


//
// setup boot variable
//
ap: set BOOT flash:/c1200-k9w7-mx.123-8.JED/c1200-k9w7-mx.123-8.JED

// That's it - now you can reload your AP.


//
// TIP: use set command to display variable values
//
ap: set
BOOT=flash:/c1200-k9w7-mx.123-8.JED/c1200-k9w7-mx.123-8.JED
DEFAULT_GATEWAY=192.168.0.1
DEFAULT_ROUTER=192.168.0.1
IP_ADDR=192.168.0.105
IP_ADDRESS=192.168.0.105
IP_SUBNET_MASK=255.255.255.0
NETMASK=255.255.255.0
RELOAD_REASON=41
ROM_PERSISTENT_UTC=1445179570


Sources

  1. https://supportforums.cisco.com/(…)

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